1657720800
An Opiniated Generator for OpenAPI Definitions For Dart
openapi_schema_generator
An opiniated generator for OpenAPI definitions.
It only works for a subset of definitions and aims to make generated code more human readable by using freezed package for modeling data.
Install
> dart pub global activate openapi_schema_generator
Usage
> dart pub global run openapi_schema_generator:generate -o ./package/ ./definitions/pets.json
For generating models :
cd package
flutter pub get
flutter pub run build_runner build
Definition rules #
- All schemas must be defined in
components.schemaand referenced from child objects and routes. - Route parameters must be of basic types (
string,integer,number).
FAQ
Why don`t you simply use the official OpenAPI generator ?
The OpenAPI official generator supports dart language, but the generated code seems over complicated in my opinion. It also generates mutable objects which makes object instantiation less simple that a simply constructor/copyWith combination.
And the other reason is that oneOf isn't supported yet for Dart.
What do you mean by "opiniated"?
The supported definition subset is only designed to support my own needs. So there are specific rules that may not fit the way you write your OpenAPI definitions, but this limitations allow me to simplify the maintenance since I work on it alone, on my spare time.
Where can I find an example supported definition and generated code ?
You have one in the repository.
Use this package as an executable
Install it
You can install the package from the command line:
dart pub global activate openapi_schema_generatorUse it
The package has the following executables:
$ generateAuthor:
Source code: https://pub.dev/packages/openapi_schema_generator/install
License:
#flutter #dart
What is GEEK
Buddha Community
1648873833
A Collection of Flutter and Dart Tips and Tricks
Table of Contents
LazyStreamin Flutter and Dart- Cancelable APIs in Flutter
- Asset Data in Flutter
- API Caching in Flutter
FutureGroupin Dart- Flatten
Iterable<bool>in Dart - Caching Temp Files in Flutter
- Custom Lists in Dart
- Optional Chaining in Dart
- MapList in Flutter
Future<bool>in Flutter- Async Bloc Init in Flutter
- Firebase Auth Errors in Flutter
- Debug Strings in Flutter
- Keyboard Appearance in Flutter
- Get
StringData in Dart Stream.startWithin Flutter- Optional Functions in Dart
AnnotatedRegionin Flutter- Unordered
MapEquality in Dart IterabletoListViewin Flutter- Password Mask in Flutter
- Fast
Object.toString()in Dart - Copying Bloc State in Flutter
IterableSubscripts in DartuseStatein Flutter Hooks- Folding Iterables in Dart
- Custom Iterables in Dart
- Class Clusters in Dart
Iterable+/- in Dart- Periodic Streams in Dart
EmptyOnErrorin DartStream<T>Initial Value in FlutterDouble.normalizein Dart- Hide Sensitive Information in Flutter
Iterable.compactMapin DartuseEffectin Flutter Hooks- Merging Streams in Dart
IsolateStream in Dart- Network Image Retry in Flutter
- Reusable APIs in Flutter
ListTileShadow in Flutter- Transparent AppBar in Flutter
- Constructors on Abstract Classes in Dart
@useResultin Dart@mustCallSuperin DartObject.hashin Dart- Expanded Equally in Flutter
- Random Iterable Value in Dart
- Hardcoded Strings in Flutter
- Manually Scroll in List View in Flutter
AsyncSnapshottoWidgetin Flutter- Breadcrumbs in Flutter
- Unique
MapValues in Dart - Smart Quotes/Dashes in Flutter
- Haptic Feedback in Flutter
- Localization Delegates in Flutter
- Extending Functions in Dart
- Paginated
ListViewin Flutter - Immutable Classes in Dart
- Card Widget in Flutter
- List Equality Ignoring Ordering in Dart
- Shorten GitHub URLs in Dart
- Time Picker in Flutter
- Throttled Print in Flutter
- Map Equality in Dart
- Unique Maps in Dart
- Raw Auto Complete in Flutter
- Title on
Objectin Dart - Compute in Flutter
- Filter on
Mapin Dart - Type Alias in Dart
ValueNotifierin Flutter- Object to Integer in Dart
- Image Opacity in Flutter
- Covariant in Dart
- Custom Errors in Streams in Dart
- Shake Animation in Flutter
- Throw Enums in Dart
FutureError Test in Flutter- Generic URL Retrieval in Dart
- Custom Error Widget in Flutter
- Handle Multiple
FutureErrors in Dart FutureError Handling in Dart- String to Toast in Flutter
- Waiting in Dart
- Loading Dialog in Flutter
- Compact Map on
Map<K,V>in Dart - Query Parameters in Dart
- Multiple Gradients in Container in Flutter
- Filter on
Stream<List<T>>in Dart - Generic Route Arguments in Flutter
- Generic Dialog in Flutter
- GitHub API in Flutter
ChangeNotifierin Flutter- Refresh Indicator in Flutter
- FlatMap in Dart
OrientationBuilderin Flutter- Linear Gradient in Flutter
- Bloc Text Editing Controller in Flutter
- Blurred TabBar in Flutter
- Play YouTube in Flutter
- ListView Background in Flutter
- Integer to Binary in Dart
- Split String by Length in Dart
- Image Tint in Flutter
- SlideTransition in Flutter
- Expansion Panels and Lists in Flutter
- Complete CRUD App in Flutter
- SQLite Storage in Flutter
- Circular Progress with Percentage in Flutter
- Opening URLs in Flutter
- Commodore 64 Screen in Flutter
- Animated Lists in Flutter
CheckboxListTilein Flutter-Operator onStringin Dart- Dart Progress for
Future<T> - Move Widget Shadows with Animation
- Gallery with Blurred Backgrounds in Flutter
- Custom Path Clippers in Flutter
- Frost Effect on Images in Flutter
- Custom Clippers in Flutter
- Check if Website is Up or Down in Dart
- Section Titles on ListView in Flutter
- Circular Progress in Flutter
- Displaying Scroll Wheels in Flutter
- Post Messages to Slack with Dart
- Unwrap
List<T?>?in Dart - Avoiding UI Jitters When Switching Widgets in Flutter
- Detect Redirects in Dart
- Proportional Constraints in Flutter
- Displaying Cupertino Action Sheets in Flutter
- Rotating
List<T>in Dart - Displaying SnackBars in Flutter
- Custom Tab Bar Using ToggleButtons in Flutter
- Hashable Mixins in Dart
- Flutter Tips and Tricks in Terminal
- Searching
List<List<T>>in Dart - Cloning Objects in Dart
- Color Filters in Flutter
- Flattening Lists in Dart
- Managing Duplicates in
List<T>in Dart - FlatMap and CompactMap in Dart
- Equality of
List<T>in Dart - Constants in Dart
- Displaying Scrollable Bottom Sheets in Flutter
- YouTube Ad Remover in Dart
- Fade Between Widgets in Flutter
- Sort Descriptors in Dart
- User Sortable Columns and Tables in Flutter
- Content-Length of
List<Uri>in Dart - Recursive Dot Notation on Maps in Dart
- Allow User Selection of Text in Flutter
- Placing Constraints on Widgets in Flutter
- Animating Position Changes in Flutter
- Transitioning Between Widgets in Flutter
- Doubly Linked Lists in Dart
- Reordering Items Inside List Views in Flutter
- Custom Stream Transformers in Dart
- Expanding Stream Elements in Dart
- Consume Streams for a Duration in Dart
- Shortening URLs in Dart
- LimitedBox Widget as ListView Items in Flutter
- Generically Convert Anything to Int in Dart
- Validating URL Certificates in Dart
- Displaying Popup Menus in Flutter
- Implementing Drag and Drop in Flutter
- Dismissing List Items in Flutter
- Animating Widgets with Ease in Flutter
- Displaying Tool Tips in Flutter
- Displaying Assorted Widgets Inside TableView in Flutter
- Page Indicator with Page View in Flutter
- Animating and Moving a Floating Action Button in Flutter
- Fading Network Image Widget in Flutter
- Transparent Alert Dialogs in Flutter
- Network Image Size in Dart
- Animated Icons in Flutter
- Custom Scroll Views in Flutter
- Parallax App Bar in Flutter
- JSON HTTP Requests in Dart
- URL Timeouts in Dart
- Detecting URL File Types in Dart
- Paginated Lists in Dart
- Requesting DELETE on APIs in Dart
- Animated Containers in Flutter
- Hiding Widgets in Flutter
- Simple Opacity Animation in Flutter
- Vignette Widget in Flutter
- Drop Down Button Configuration and Usage in Flutter
- Expandable List Items in Flutter
- Infinite Scrolling in Flutter
- Infinite Arrays in Dart
- Custom Color Picker Component in Flutter
- Displaying and Reacting to Switches in Flutter
- Displaying Bottom Bars in Flutter
- Displaying Buttons on AppBar in Flutter
- Displaying Bottom Sheets in Flutter
- Converting Enums to Radio Buttons in Flutter
- Check Existence of Websites in Flutter
- Images inside AlertDialog in Flutter
- Returning Values from AlertDialog in Flutter
- Simple Grid View in Flutter
- Rendering Bullet Points in Flutter
- Retrying Futures in Flutter
- Containers as ClipOvals in Flutter
- Rich Texts in Flutter
- Wrapping Widgets in Flutter
- Sweep Gradients in Flutter
StreamandStreamBuilderin Flutter- Blur Effect in Flutter
- Convert Enums to Strings in Dart
- Replacing Text in TextField in Flutter
- Aspect Ratio in Flutter
- Zoom and Pan in Flutter
- Resizing Images in Flutter to Fit Screen Height
- Validating URLs in Flutter
- FrameBuilder for Network Images in Flutter
- Adding Shadow to Icons in Flutter
- Calculating Median of Lists in Dart
- Generic Functions with Reduce in Dart
- Passing Back Data From a Screen to the Previous One in Flutter
- Flinging an Animation in Flutter
- Fade Animations in Flutter
- Throttling User Input in Flutter
- Censoring TextFields in Flutter
- Customizing TextButton in Flutter
- Multiline TextFields in Flutter
- Filtering TextField Input in Flutter
- Focusing Manually on TextFields in Flutter
- Data Streams Over HTTP/HTTPs in Dart
- Catching Nonexistent Accessors or Methods in Dart
- Using Expando in Dart
- Implementing Custom Maps in Dart
- Dynamically Calling Functions in Dart
- Factory Constructors in Dart
- Calculating the Sum of List Items in Dart
- Removing Duplicate Strings in Lists in Dart (Case-Insensitive)
- Implementing Range in Dart
- Converting Lists to Maps in Dart
- Implementing Hashable in Dart
- Random Name Generator in Dart
- Capturing Stack Traces in Dart Exceptions
- Removing Duplicates from Lists in Dart
- Optional Spread Operator in Dart
- Calling Optional Functions in Dart
- Odd-Even Sort in Dart
- Implementing Zip and Tuples in Dart
- Swapping Values in Lists with XOR in Dart
- Waiting for Multiple Futures in Dart
- Using Queues as Stacks in Dart
- Custom Iterators in Dart
- Iterables as Ranges + Transform in Dart
- Errors vs Exceptions in Dart
- Custom Annotations in Dart
- Classes as Enums in Dart
- Spread Operator in Collection Literals in Dart
StreamBuilderandStreamControllerin Dart- Almost Equal in Dart
- Enum Associated Values in Dart
- Implementing
Comparablein Dart - Implementing Custom Integer Types in Dart
- Custom Subscripts in Dart
- Dart List Enumeration with Index
- Applying Mixins to Other Mixins in Dart
- Parameter Types in Dart
- Custom Exceptions in Dart
rethrowing Exceptions in Dartmixins and JSON Parsing in Dartmixins vsabstract classes in Dart- Drawing Shapes in Flutter with
LayoutBuilder,CustomPaintandCustomPainter - Generic Type Aliases in Dart
- Callable Classes in Dart
- Synchronous Generators in Dart
- Implicit Interfaces in Dart
constConstructors in Dartasync-awaitOver RawFutures in Dart- Initializer List and Default Values as Convenience Intializers in Dart
- Extract Elements of Certain Type from Lists in Dart
- Type Promotion in Dart
- Extract Minimum and Maximum Values in
List<num>in Dart - Functions as First Class Citizens in Dart
LazyStream in Flutter and Dart
import 'dart:developer' as devtools show log;
import 'dart:typed_data' show Uint8List;
import 'package:flutter/services.dart' show NetworkAssetBundle, rootBundle;
import 'package:async/async.dart' show LazyStream;
extension LocalFileData on String {
Future<Uint8List> localFileData() => rootBundle.load(this).then(
(byteData) => byteData.buffer.asUint8List(),
);
}
extension Log on Object {
void log() => devtools.log(toString());
}
void testIt() async {
final stream = LazyStream(
() async {
final allData = await calculateAllData();
return getImagesData(allData);
},
);
await for (final data in stream) {
'Got data, length = ${data.length}'.log();
}
}
Stream<Uint8List> getImagesData(
List<Future<Uint8List>> allData,
) async* {
for (final data in allData) {
yield await data;
}
}
Future<List<Future<Uint8List>>> calculateAllData() async {
final futures = Iterable.generate(
3,
(i) => 'images/image_list${i + 1}.txt'
.localFileData()
.then((data) => String.fromCharCodes(data)),
);
final result = Future.wait(futures);
final lineSplitter = const LineSplitter();
List<Future<Uint8List>> allData = [];
for (final string in await result) {
final urls = lineSplitter.convert(string);
for (final url in urls) {
allData.add(
NetworkAssetBundle(Uri.parse(url))
.load(url)
.then((byteData) => byteData.buffer.asUint8List()),
);
}
}
return allData;
}
Cancelable APIs in Flutter
import 'dart:developer' as devtools show log;
import 'dart:typed_data' show Uint8List;
import 'package:flutter/services.dart' show NetworkAssetBundle, rootBundle;
import 'package:async/async.dart' show CancelableOperation;
extension Log on Object {
void log() => devtools.log(toString());
}
extension LocalFileData on String {
Future<Uint8List> localFileData() => rootBundle.load(this).then(
(byteData) => byteData.buffer.asUint8List(),
);
}
CancelableOperation<Uint8List> getImageOperation(String url) =>
CancelableOperation.fromFuture(
NetworkAssetBundle(Uri.parse(url))
.load(url)
.then((byteData) => byteData.buffer.asUint8List()),
onCancel: () => 'images/template.png'.localFileData(),
);
void testIt() async {
final operation = getImageOperation('http://127.0.0.1:5500/images/1.png');
final cancelledValue = await operation.cancel();
final result = await operation.valueOrCancellation(cancelledValue);
result?.log();
}
Asset Data in Flutter
import 'dart:typed_data' show Uint8List;
import 'package:flutter/services.dart' show rootBundle;
import 'dart:developer' as devtools show log;
extension Log on Object {
void log() => devtools.log(toString());
}
extension LocalFileData on String {
Future<Uint8List> localFileData() => rootBundle.load(this).then(
(byteData) => byteData.buffer.asUint8List(),
);
}
void testIt() async {
(await 'images/template.png'.localFileData()).log();
}
API Caching in Flutter
import 'dart:typed_data' show Uint8List;
import 'package:flutter/services.dart' show NetworkAssetBundle;
import 'dart:developer' as devtools show log;
import 'package:async/async.dart' show AsyncMemoizer;
extension Log on Object {
void log() => devtools.log(toString());
}
@immutable
class GetImageApi {
final String url;
final _fetch = AsyncMemoizer<Uint8List>();
GetImageApi({required this.url});
Future<Uint8List> fetch() => _fetch.runOnce(
() => NetworkAssetBundle(Uri.parse(url))
.load(url)
.then((byteData) => byteData.buffer.asUint8List()),
);
}
void testIt() async {
final api = GetImageApi(url: 'http://127.0.0.1:5500/images/1.png');
(await api.fetch()).log(); // fetched
(await api.fetch()).log(); // cached
}
FutureGroup in Dart
mixin FutureConvertible<T> {
Future<T> toFuture();
}
@immutable
class LoginApi with FutureConvertible<bool> {
@override
Future<bool> toFuture() => Future.delayed(
const Duration(seconds: 1),
() => true,
);
}
@immutable
class SignUpApi with FutureConvertible<bool> {
@override
Future<bool> toFuture() => Future.delayed(
const Duration(seconds: 1),
() => true,
);
}
extension Flatten on Iterable<bool> {
bool flatten() => fold(
true,
(lhs, rhs) => lhs && rhs,
);
}
extension Log on Object {
void log() => devtools.log(toString());
}
Future<bool> startup({
required bool shouldLogin,
required bool shouldSignUp,
}) {
final group = FutureGroup<bool>();
if (shouldLogin) {
group.add(LoginApi().toFuture());
}
if (shouldSignUp) {
group.add(SignUpApi().toFuture());
}
group.close();
return group.future.then((bools) => bools.flatten());
}
void testIt() async {
final success = await startup(
shouldLogin: true,
shouldSignUp: false,
);
success.log();
}
Flatten Iterable<bool> in Dart
extension Flatten on Iterable<bool> {
bool flatten() => fold(
true,
(lhs, rhs) => lhs && rhs,
);
}
void testIt() {
assert([true, false, true].flatten() == false);
assert([true, true, true].flatten() == true);
assert([false, false, false].flatten() == false);
assert([true].flatten() == true);
assert([false].flatten() == false);
}
Caching Temp Files in Flutter
@immutable
class NetworkImageAsset {
final String localPath;
final String url;
NetworkImageAsset({required int index})
: localPath = Directory.systemTemp.path + '/$index.png',
url = 'http://127.0.0.1:5500/images/$index}.png';
Future<bool> downloadAndSave() => NetworkAssetBundle(Uri.parse(url))
.load(url)
.then((byteData) => byteData.buffer.asUint8List())
.then((data) => File(localPath).writeAsBytes(data).then((_) => true))
.catchError((_) => false);
}
void testIt() async {
await Future.forEach(
Iterable.generate(
3,
(i) => NetworkImageAsset(index: i + 1),
),
(NetworkImageAsset asset) => asset.downloadAndSave(),
);
}
Custom Lists in Dart
import 'dart:developer' as devtools show log;
import 'dart:collection' show ListBase;
class LowercaseList extends ListBase<String> {
final List<String> _list = [];
@override
int get length => _list.length;
@override
set length(int newLength) => _list.length = newLength;
@override
String operator [](int index) => _list[index].toUpperCase();
@override
void operator []=(int index, value) => _list[index] = value;
@override
void addAll(Iterable<String> iterable) => _list.addAll(iterable);
@override
void add(String element) => _list.add(element);
}
extension Log on Object {
void log() => devtools.log(toString());
}
void testIt() {
final myList = LowercaseList();
myList.addAll(['foo', 'bar', 'baz']);
myList[0].log(); // FOO
myList[1].log(); // BAR
for (final item in myList) {
item.log(); // FOO, BAR, BAZ
}
}
Optional Chaining in Dart
@immutable
class Address {
final String? firstLine;
final String? secondLine;
const Address(this.firstLine, this.secondLine);
}
@immutable
class Person {
final Person? father;
final Address? address;
const Person(this.father, this.address);
}
extension GetFathersFirstAddressLine on Person {
String? get firstAddressLineOfFather => father?.address?.firstLine;
}
MapList in Flutter
extension MapToList<T> on Iterable<T> {
List<E> mapList<E>(E Function(T) toElement) =>
map(toElement).toList();
}
Future<bool> in Flutter
Future<bool> uploadImage({
required File file,
required String userId,
}) =>
FirebaseStorage.instance
.ref(userId)
.child(const Uuid().v4())
.putFile(file)
.then((_) => true)
.catchError((_) => false);
Async Bloc Init in Flutter
class App extends StatelessWidget {
const App({
Key? key,
}) : super(key: key);
@override
Widget build(BuildContext context) {
return BlocProvider<AppBloc>(
create: (context) => AppBloc()..add(const AppEventInitialize()),
child: MaterialApp(
title: 'Photo Library',
theme: ThemeData(
primarySwatch: Colors.blue,
),
debugShowCheckedModeBanner: false,
home: BlocConsumer<AppBloc, AppState>(
listener: (context, state) {
// handle loading
if (state.isLoading) {
LoadingScreen().show(
context: context,
text: 'Loading...',
);
} else {
LoadingScreen().hide();
}
... rest of your code goes here
Firebase Auth Errors in Flutter
const authErrorMapping = {
'user-not-found': AuthErrorUserNotFound(),
'project-not-found': AuthErrorProjectNotFound(),
};
@immutable
abstract class AuthError {
factory AuthError.from(FirebaseAuthException exception) =>
authErrorMapping[exception.code.toLowerCase().trim()] ??
const AuthErrorUnknown();
}
@immutable
class AuthErrorUnknown implements AuthError {
const AuthErrorUnknown();
}
@immutable
class AuthErrorUserNotFound implements AuthError {
const AuthErrorUserNotFound();
}
@immutable
class AuthErrorProjectNotFound implements AuthError {
const AuthErrorProjectNotFound();
}
Debug Strings in Flutter
extension IfDebugging on String {
String? get ifDebugging => kDebugMode ? this : null;
}
class LoginView extends HookWidget {
const LoginView({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
final emailController = useTextEditingController(
text: 'foo@bar.com'.ifDebugging,
);
final passwordController = useTextEditingController(
text: 'foobarbaz'.ifDebugging,
);
// rest of your code would be here ...
Keyboard Appearance in Flutter
class LoginView extends HookWidget {
const LoginView({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: const Text('Log in'),
),
body: Padding(
padding: const EdgeInsets.all(8.0),
child: Column(
children: const [
TextField(
keyboardType: TextInputType.emailAddress,
keyboardAppearance: Brightness.dark,
),
TextField(
obscureText: true,
obscuringCharacter: '◉',
),
],
),
),
);
}
}
Get String Data in Dart
extension ToList on String {
Uint8List toUint8List() => Uint8List.fromList(codeUnits);
}
final text1Data = 'Foo'.toUint8List();
final text2Data = 'Bar'.toUint8List();
Stream.startWith in Flutter
import 'package:async/async.dart' show StreamGroup;
import 'dart:developer' as devtools show log;
extension Log on Object {
void log() => devtools.log(toString());
}
extension StartWith<T> on Stream<T> {
Stream<T> startWith(T value) => StreamGroup.merge([
this,
Stream<T>.value(value),
]);
}
void testIt() {
Stream.periodic(const Duration(seconds: 1), (i) => i + 1)
.startWith(0)
.take(4)
.forEach((element) {
element.log();
}); // 0, 1, 2, 3
}
Optional Functions in Dart
typedef AppBlocRandomUrlPicker = String Function(Iterable<String> allUrls);
extension RandomElement<T> on Iterable<T> {
T getRandomElement() => elementAt(
math.Random().nextInt(length),
);
}
class AppBloc extends Bloc<AppEvent, AppState> {
String _pickRandomUrl(Iterable<String> allUrls) => allUrls.getRandomElement();
AppBloc({
required Iterable<String> urls,
AppBlocRandomUrlPicker? urlPicker,
}) : super(const AppState.empty()) {
on<LoadNextUrlEvent>(
(event, emit) {
emit(
const AppState(
isLoading: true,
data: null,
),
);
// pick a random URL to load
final url = (urlPicker ?? _pickRandomUrl)(urls);
HttpClient().getUrl(Uri.parse(url)); // continue here...
},
);
}
}
AnnotatedRegion in Flutter
class HomePage extends StatelessWidget {
const HomePage({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
return Scaffold(
body: AnnotatedRegion<SystemUiOverlayStyle>(
value: SystemUiOverlayStyle.dark,
child: Column(
mainAxisSize: MainAxisSize.max,
children: [
Expanded(child: Container(color: Colors.blue)),
Expanded(child: Container(color: Colors.yellow)),
],
),
),
);
}
}
Unordered Map Equality in Dart
import 'package:collection/collection.dart';
import 'dart:developer' as devtools show log;
extension Log on Object {
void log() => devtools.log(toString());
}
extension UnorderedEquality<K, V> on Map<K, V> {
bool isEqualTo(Map<K, V> other) =>
const DeepCollectionEquality.unordered().equals(this, other);
}
void testIt() {
final dict1 = {
'name': 'foo',
'age': 20,
'values': ['foo', 'bar'],
};
final dict2 = {
'age': 20,
'name': 'foo',
'values': ['bar', 'foo'],
};
dict1.isEqualTo(dict2).log(); // true
}
Iterable to ListView in Flutter
extension ToListView<T> on Iterable<T> {
Widget toListView() => IterableListView(
iterable: this,
);
}
class IterableListView<T> extends StatelessWidget {
final Iterable<T> iterable;
const IterableListView({
Key? key,
required this.iterable,
}) : super(key: key);
@override
Widget build(BuildContext context) {
return ListView.builder(
itemCount: iterable.length,
itemBuilder: (context, index) {
return ListTile(
title: Text(
iterable.elementAt(index).toString(),
),
);
},
);
}
}
@immutable
class Person {
final String name;
final int age;
const Person({required this.name, required this.age});
@override
String toString() => '$name, $age years old';
}
const persons = [
Person(name: 'Foo', age: 20),
Person(name: 'Bar', age: 30),
Person(name: 'Baz', age: 40),
];
class HomePage extends StatelessWidget {
const HomePage({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: const Text('Home Page'),
),
body: persons.toListView(),
);
}
}
Password Mask in Flutter
class PasswordTextField extends StatelessWidget {
const PasswordTextField({
Key? key,
required this.passwordController,
}) : super(key: key);
final TextEditingController passwordController;
@override
Widget build(BuildContext context) {
return TextField(
controller: passwordController,
obscureText: true,
obscuringCharacter: '◉',
decoration: const InputDecoration(
hintText: 'Enter your password here...',
),
);
}
}
Fast Object.toString() in Dart
@immutable
class AppState {
final bool isLoading;
final Object? loginError;
final String? loginHandle;
final Iterable<String>? fetchedNotes;
@override
String toString() => {
'isLoading': isLoading,
'loginError': loginError,
'loginHandle': loginHandle,
'fetchedNotes': fetchedNotes
}.toString();
const AppState({
required this.isLoading,
required this.loginError,
required this.loginHandle,
required this.fetchedNotes,
});
}
Copying Bloc State in Flutter
@immutable
class AppState {
final bool isLoading;
final LoginHandle? loginHandle;
final Iterable<Note>? fetchedNotes;
const AppState.empty()
: isLoading = false,
loginHandle = null,
fetchedNotes = null;
const AppState({
required this.isLoading,
required this.loginHandle,
required this.fetchedNotes,
});
AppState copiedWith({
bool? isLoading,
LoginHandle? loginHandle,
Iterable<Note>? fetchedNotes,
}) =>
AppState(
isLoading: isLoading ?? this.isLoading,
loginHandle: loginHandle ?? this.loginHandle,
fetchedNotes: fetchedNotes ?? this.fetchedNotes,
);
}
Iterable Subscripts in Dart
// Free Flutter Course 💙 https://linktr.ee/vandadnp
// Want to support my work 🤝? https://buymeacoffee.com/vandad
import 'dart:developer' as devtools show log;
extension Log on Object? {
void log() => devtools.log(toString());
}
extension Subscript<T> on Iterable<T> {
T? operator [](int index) => length > index ? elementAt(index) : null;
}
void testIt() {
Iterable.generate(10, (i) => i + 1)[0].log(); // 1
Iterable.generate(1, (i) => i)[2].log(); // null
Iterable.generate(10, (i) => i + 1)[9].log(); // 10
Iterable.generate(0, (i) => i)[0].log(); // null
}
useState in Flutter Hooks
import 'package:flutter_hooks/flutter_hooks.dart';
import 'dart:math' show min;
@immutable
class VirtualTab {
final Icon icon;
final String text;
const VirtualTab({
required this.icon,
required this.text,
});
}
const tabs = [
VirtualTab(
icon: Icon(Icons.picture_as_pdf),
text: 'All PDF files',
),
VirtualTab(
icon: Icon(Icons.ac_unit_outlined),
text: 'Data page',
),
VirtualTab(
icon: Icon(Icons.person),
text: 'Profile page',
),
];
class HomePage extends HookWidget {
const HomePage({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
final tabCount = useState(1);
return DefaultTabController(
length: tabCount.value,
initialIndex: tabCount.value - 1,
child: Scaffold(
appBar: AppBar(
bottom: TabBar(
tabs: tabs
.take(tabCount.value)
.map((tab) => Tab(icon: tab.icon))
.toList(),
),
),
body: CustomTabBarView(tabCount: tabCount),
),
);
}
}
class CustomTabBarView extends StatelessWidget {
const CustomTabBarView({
Key? key,
required this.tabCount,
}) : super(key: key);
final ValueNotifier<int> tabCount;
@override
Widget build(BuildContext context) {
return TabBarView(
children: tabs
.take(tabCount.value)
.map(
(tab) => Padding(
padding: const EdgeInsets.all(8.0),
child: Column(
children: [
Text(tab.text),
TextButton(
onPressed: () {
final newLength = min(
tabs.length,
tabCount.value + 1,
);
tabCount.value = newLength;
},
child: const Text('Create next tab'),
)
],
),
),
)
.toList(),
);
}
}
Folding Iterables in Dart
import 'dart:developer' as devtools show log;
extension Log on Object {
void log() => devtools.log(toString());
}
void testIt() {
final values = ['foo', 'bar', 'baz', '1.0'];
values.fold<int>(0, (pe, e) => pe + e.length); // 12
values.fold<String>('', (pe, e) => '$pe$e'); // foobarbaz1.0
values.fold<Map<String, int>>(
{},
(pe, e) => pe..addAll(<String, int>{e: e.length}),
).log(); // {foo: 3, bar: 3, baz: 3, 1.0: 3}
values.fold<double>(
0.0,
(pe, e) => pe + (double.tryParse(e) ?? 0.0),
); // 1.0
}
Custom Iterables in Dart
class Address with IterableMixin {
final String line1;
final String line2;
final String postCode;
Address({
required this.line1,
required this.line2,
required this.postCode,
});
@override
Iterator<String> get iterator => [line1, line2, postCode].iterator;
}
void testIt() {
final address = Address(
line1: 'Foo bar avenue, #10',
line2: 'Baz street',
postCode: '123456',
);
for (final line in address) {
devtools.log(line);
}
}
Class Clusters in Dart
enum AnimalType { dog, cat }
@immutable
abstract class Animal {
const Animal();
factory Animal.fromType(AnimalType type) {
switch (type) {
case AnimalType.dog:
return const Dog();
case AnimalType.cat:
return const Cat();
}
}
void makeNoise();
}
@immutable
class Dog extends Animal {
const Dog();
@override
void makeNoise() => 'Woof'.log();
}
@immutable
class Cat extends Animal {
const Cat();
@override
void makeNoise() => 'Meow'.log();
}
void testIt() {
final cat = Animal.fromType(AnimalType.cat);
cat.makeNoise();
final dog = Animal.fromType(AnimalType.dog);
dog.makeNoise();
}
Iterable +/- in Dart
extension AddRemoveItems<T> on Iterable<T> {
Iterable<T> operator +(T other) => followedBy([other]);
Iterable<T> operator -(T other) => where((element) => element != other);
}
void testIt() {
final values = ['foo', 'bar']
.map((e) => e.toUpperCase()) + 'BAZ';
values.log(); // (FOO, BAR, BAZ)
(values - 'BAZ').log(); // (FOO, BAR)
}
Periodic Streams in Dart
import 'dart:io';
import 'package:flutter/material.dart';
import 'dart:convert';
import 'dart:developer' as devtools show log;
extension Log on Object {
void log() => devtools.log(toString());
}
@immutable
class Person {
final String name;
final int age;
const Person({
required this.name,
required this.age,
});
Person.fromJson(Map<String, dynamic> json)
: name = json["name"] as String,
age = json["age"] as int;
@override
String toString() => 'Person ($name, $age years old)';
}
mixin ListOfThingsAPI<T> {
Future<Iterable<T>> get(String url) => HttpClient()
.getUrl(Uri.parse(url))
.then((req) => req.close())
.then((resp) => resp.transform(utf8.decoder).join())
.then((str) => json.decode(str) as List<dynamic>)
.then((list) => list.cast());
}
class GetPeople with ListOfThingsAPI<Map<String, dynamic>> {
Future<Iterable<Person>> getPeople(url) => get(url).then(
(jsons) => jsons.map(
(json) => Person.fromJson(json),
),
);
}
Stream<dynamic> every(Duration duration) => Stream.periodic(duration);
extension IntToDuration on int {
Duration get seconds => Duration(seconds: this);
}
void testIt() async {
await for (final people in every(3.seconds).asyncExpand(
(_) => GetPeople()
.getPeople('http://127.0.0.1:5500/apis/people1.json')
.asStream(),
)) {
people.log();
}
}
/* people1.json
[
{
"name": "Foo 1",
"age": 20
},
{
"name": "Bar 1",
"age": 30
}
]
*/
EmptyOnError in Dart
import 'dart:io';
import 'package:flutter/material.dart';
import 'dart:convert';
import 'dart:developer' as devtools show log;
extension Log on Object {
void log() => devtools.log(toString());
}
@immutable
class Person {
final String name;
final int age;
const Person({
required this.name,
required this.age,
});
Person.fromJson(Map<String, dynamic> json)
: name = json["name"] as String,
age = json["age"] as int;
@override
String toString() => 'Person ($name, $age years old)';
}
const people1Url = 'http://127.0.0.1:5500/apis/people11.json';
const people2Url = 'http://127.0.0.1:5500/apis/people2.json';
extension EmptyOnError<E> on Future<List<Iterable<E>>> {
Future<List<Iterable<E>>> emptyOnError() => catchError(
(_, __) => List<Iterable<E>>.empty(),
);
}
Future<Iterable<Person>> parseJson(String url) => HttpClient()
.getUrl(Uri.parse(url))
.then((req) => req.close())
.then((resp) => resp.transform(utf8.decoder).join())
.then((str) => json.decode(str) as List<dynamic>)
.then((json) => json.map((e) => Person.fromJson(e)));
void testIt() async {
final persons = await Future.wait([
parseJson(people1Url),
parseJson(people2Url),
]).emptyOnError();
persons.log();
}
Stream<T> Initial Value in Flutter
import 'dart:async';
import 'package:flutter/material.dart';
import 'package:flutter_hooks/flutter_hooks.dart';
void main() {
runApp(
MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
),
debugShowCheckedModeBanner: false,
home: const HomePage(),
),
);
}
const url = 'https://bit.ly/3x7J5Qt';
class HomePage extends HookWidget {
const HomePage({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
late final StreamController<double> controller;
controller = useStreamController<double>(onListen: () {
controller.sink.add(0.0);
});
return Scaffold(
appBar: AppBar(
title: const Text('Home page'),
),
body: StreamBuilder<double>(
stream: controller.stream,
builder: (context, snapshot) {
if (!snapshot.hasData) {
return const CircularProgressIndicator();
} else {
final rotation = snapshot.data ?? 0.0;
return GestureDetector(
onTap: () {
controller.sink.add(rotation + 10.0);
},
child: RotationTransition(
turns: AlwaysStoppedAnimation(rotation / 360.0),
child: Center(
child: Image.network(url),
),
),
);
}
}),
);
}
}
Double.normalize in Dart
import 'dart:developer' as devtools show log;
extension Normalize on double {
double normalized(
double selfRangeMin,
double selfRangeMax, [
double normalizedRangeMin = 0.0,
double normalizedRangeMax = 1.0,
]) =>
(normalizedRangeMax - normalizedRangeMin) *
((this - selfRangeMin) / (selfRangeMax - selfRangeMin)) +
normalizedRangeMin;
}
extension Log on Object {
void log() => devtools.log(toString());
}
void testIt() async {
2.0.normalized(0, 2.0).log(); // 1.0
4.0.normalized(0, 8.0).log(); // 0.5
5.0.normalized(4.0, 6.0, 10.0, 20.0).log(); // 15
}
Hide Sensitive Information in Flutter
import 'package:flutter/material.dart';
import 'package:flutter_hooks/flutter_hooks.dart';
void main() {
runApp(
MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
),
debugShowCheckedModeBanner: false,
home: const HomePage(),
),
);
}
class HomePage extends HookWidget {
const HomePage({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
final state = useAppLifecycleState();
return Scaffold(
appBar: AppBar(
title: const Text('Home Page'),
),
body: Padding(
padding: const EdgeInsets.all(8.0),
child: Opacity(
opacity: state == AppLifecycleState.resumed ? 1.0 : 0.0,
child: Container(
decoration: BoxDecoration(
boxShadow: [
BoxShadow(
blurRadius: 10,
color: Colors.black.withAlpha(100),
spreadRadius: 10,
),
],
),
child: Image.asset('assets/card.png'),
),
),
),
);
}
}
Iterable.compactMap in Dart
import 'dart:developer' as devtools show log;
extension Log on Object {
void log() => devtools.log(toString());
}
extension CompactMap<T> on Iterable<T?> {
Iterable<T> compactMap<E>([
E? Function(T?)? transform,
]) =>
map(transform ?? (e) => e).where((e) => e != null).cast();
}
const list = ['Hello', null, 'World'];
void testIt() {
list.log(); // [Hello, null, World]
list.compactMap().log(); // [Hello, World]
list.compactMap((e) => e?.toUpperCase()).log(); // [HELLO, WORLD]
}
useEffect in Flutter Hooks
import 'package:flutter/material.dart';
import 'package:flutter_hooks/flutter_hooks.dart';
void main() {
runApp(
MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
),
debugShowCheckedModeBanner: false,
home: const HomePage(),
),
);
}
class HomePage extends HookWidget {
const HomePage({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
final controller = useTextEditingController();
final text = useState('');
useEffect(
() {
void listener() {
text.value = controller.text;
}
controller.addListener(listener);
return () => controller.removeListener(listener);
},
[controller],
);
return Scaffold(
body: Column(
children: [
TextField(
controller: controller,
),
Text('You typed ${text.value}')
],
),
);
}
}
Merging Streams in Dart
import 'package:async/async.dart' show StreamGroup;
import 'dart:developer' as devtools show log;
extension Log on Object {
void log() => devtools.log(toString());
}
void testIt() async {
final streams = Iterable.generate(
3,
(i) => Stream.periodic(
const Duration(seconds: 1),
(_) => 'Stream $i: ${DateTime.now().toIso8601String()}',
).take(i + 1),
);
await for (final now in StreamGroup.merge(streams)) {
now.log();
}
}
Isolate Stream in Dart
Stream<String> getMessages() {
final rp = ReceivePort();
return Isolate.spawn(_getMessages, rp.sendPort)
.asStream()
.asyncExpand((_) => rp)
.takeWhile((element) => element is String)
.cast();
}
void _getMessages(SendPort sp) async {
await for (final now in Stream.periodic(
const Duration(seconds: 1),
(_) => DateTime.now().toIso8601String(),
).take(10)) {
sp.send(now);
}
Isolate.exit(sp);
}
void testIt() async {
await for (final msg in getMessages()) {
msg.log();
}
}
Network Image Retry in Flutter
@immutable
class RetryStrategy {
final bool shouldRetry;
final Duration waitBeforeRetry;
const RetryStrategy({
required this.shouldRetry,
required this.waitBeforeRetry,
});
}
typedef Retrier = RetryStrategy Function(String url, Object error);
class NetworkImageWithRetry extends StatelessWidget {
final Widget loadingWidget;
final Widget errorWidget;
final String url;
final Retrier retrier;
final _controller = StreamController<Uint8List>.broadcast();
NetworkImageWithRetry({
Key? key,
required this.url,
required this.retrier,
required this.loadingWidget,
required this.errorWidget,
}) : super(key: key);
void getData() async {
while (true == true) {
try {
final networkAsset = NetworkAssetBundle(Uri.parse(url));
final loaded = await networkAsset.load(url);
final bytes = loaded.buffer.asUint8List();
_controller.sink.add(bytes);
break;
} catch (e) {
final strategy = retrier(url, e);
if (strategy.shouldRetry) {
await Future.delayed(strategy.waitBeforeRetry);
} else {
_controller.sink.addError(e);
break;
}
}
}
}
@override
Widget build(BuildContext context) {
getData();
return StreamBuilder(
stream: _controller.stream,
builder: (context, AsyncSnapshot<Uint8List> snapshot) {
if (snapshot.hasError) {
return errorWidget;
} else {
final data = snapshot.data;
if (snapshot.hasData && data != null) {
return Image.memory(data);
} else {
return loadingWidget;
}
}
},
);
}
}
class HomePage extends StatelessWidget {
const HomePage({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: const Text('Image Retry'),
),
body: NetworkImageWithRetry(
url: 'https://bit.ly/3qYOtDm',
errorWidget: const Text('Got an error!'),
loadingWidget: const Text('Loading...'),
retrier: (url, error) {
return RetryStrategy(
shouldRetry: error is! FlutterError,
waitBeforeRetry: const Duration(seconds: 1),
);
},
),
);
}
}
Reusable APIs in Flutter
import 'dart:io';
import 'package:flutter/material.dart';
import 'dart:developer' as devtools show log;
import 'dart:convert' show utf8;
import 'package:meta/meta.dart' show useResult;
extension Log on Object {
void log() => devtools.log(toString());
}
extension GetOnUri on Object {
Future<HttpClientResponse> getUrl(
String url,
) =>
HttpClient()
.getUrl(
Uri.parse(
url,
),
)
.then((req) => req.close());
}
mixin CanMakeGetCall {
String get url;
@useResult
Future<String> getString() => getUrl(url).then(
(response) => response
.transform(
utf8.decoder,
)
.join(),
);
}
@immutable
class GetPeople with CanMakeGetCall {
const GetPeople();
@override
String get url => 'http://127.0.0.1:5500/apis/people.json';
}
void testIt() async {
final people = await const GetPeople().getString();
devtools.log(people);
}
ListTile Shadow in Flutter
enum Currency { dollars }
extension Title on Currency {
String get title {
switch (this) {
case Currency.dollars:
return '\$';
}
}
}
@immutable
class Item {
final IconData icon;
final String name;
final double price;
final Currency currency;
const Item({
required this.icon,
required this.name,
required this.price,
required this.currency,
});
String get description => '$price${currency.title}';
}
const items = [
Item(
icon: Icons.camera_alt,
name: 'Camera',
price: 300,
currency: Currency.dollars,
),
Item(
icon: Icons.house,
name: 'House',
price: 1000000,
currency: Currency.dollars,
),
Item(
icon: Icons.watch,
name: 'Smart Watch',
price: 200,
currency: Currency.dollars,
),
];
class HomePage extends StatefulWidget {
const HomePage({Key? key}) : super(key: key);
@override
_HomePageState createState() => _HomePageState();
}
class _HomePageState extends State<HomePage> {
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: const Text('Home Page'),
),
body: ListView.builder(
itemCount: items.length,
itemBuilder: (_, index) {
return ItemTile(
item: items[index],
);
},
),
);
}
}
class ItemTile extends StatelessWidget {
final Item item;
const ItemTile({Key? key, required this.item}) : super(key: key);
@override
Widget build(BuildContext context) {
return Padding(
padding: const EdgeInsets.all(8.0),
child: Stack(
children: [
const TileBackground(),
CustomTile(item: item),
],
),
);
}
}
class CustomTile extends StatelessWidget {
final Item item;
const CustomTile({
Key? key,
required this.item,
}) : super(key: key);
@override
Widget build(BuildContext context) {
return Padding(
padding: const EdgeInsets.only(bottom: 7.0),
child: Container(
decoration: customDecoration(),
child: ListTile(
leading: Icon(
item.icon,
color: Colors.white,
),
title: Text(item.name),
subtitle: Text(item.description),
),
),
);
}
}
BoxDecoration customDecoration() {
return BoxDecoration(
color: const Color.fromARGB(255, 0x7d, 0xcf, 0xff),
borderRadius: BorderRadius.circular(10.0),
border: Border.all(
color: Colors.black,
width: 2.0,
),
);
}
class TileBackground extends StatelessWidget {
const TileBackground({
Key? key,
}) : super(key: key);
@override
Widget build(BuildContext context) {
return Positioned.fill(
child: Padding(
padding: const EdgeInsets.symmetric(horizontal: 6.0),
child: Container(
decoration: BoxDecoration(
color: const Color.fromARGB(255, 202, 255, 127),
borderRadius: BorderRadius.circular(10.0),
border: Border.all(
color: Colors.black,
width: 2.0,
),
),
),
),
);
}
}
Transparent AppBar in Flutter
const images = [
'https://bit.ly/3x7J5Qt',
'https://bit.ly/3ywI8l6',
'https://bit.ly/36fNNj9',
'https://bit.ly/3jOueGG',
'https://bit.ly/3qYOtDm',
'https://bit.ly/3wt11Ec',
'https://bit.ly/3yvFg7X',
'https://bit.ly/3ywzOla',
'https://bit.ly/3wnASpW',
'https://bit.ly/3jXSDto',
];
class HomePage extends StatelessWidget {
const HomePage({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
return Scaffold(
extendBodyBehindAppBar: true,
appBar: AppBar(
elevation: 0.0,
backgroundColor: Colors.blueAccent.withAlpha(200),
title: const Text('Transparent App Bar in Flutter'),
),
body: const ImagesScrollView(),
);
}
}
class ImagesScrollView extends StatelessWidget {
const ImagesScrollView({
Key? key,
}) : super(key: key);
@override
Widget build(BuildContext context) {
return SingleChildScrollView(
padding: const EdgeInsets.only(top: 80.0),
child: Padding(
padding: const EdgeInsets.only(
top: 40.0,
left: 10.0,
right: 10.0,
),
child: Column(
children: images
.map((url) => ElevatedNetworkImage(url: url))
.expand(
(img) => [
img,
const SizedBox(height: 30.0),
],
)
.toList(),
),
),
);
}
}
class ElevatedNetworkImage extends StatelessWidget {
final String url;
const ElevatedNetworkImage({Key? key, required this.url}) : super(key: key);
@override
Widget build(BuildContext context) {
return PhysicalShape(
color: Colors.white,
clipper: Clipper(),
elevation: 20.0,
clipBehavior: Clip.none,
shadowColor: Colors.white.withAlpha(200),
child: CutEdges(
child: Image.network(url),
),
);
}
}
class Clipper extends CustomClipper<Path> {
static const variance = 0.2;
static const reverse = 1.0 - variance;
@override
Path getClip(Size size) {
final path = Path();
path.moveTo(0.0, size.height * Clipper.variance);
path.lineTo(size.width * Clipper.variance, 0.0);
path.lineTo(size.width, 0.0);
path.lineTo(size.width, size.height * Clipper.reverse);
path.lineTo(size.width * Clipper.reverse, size.height);
path.lineTo(0.0, size.height);
path.lineTo(0.0, size.height * Clipper.variance);
path.close();
return path;
}
@override
bool shouldReclip(covariant CustomClipper<Path> oldClipper) => false;
}
class CutEdges extends StatelessWidget {
final Widget child;
const CutEdges({Key? key, required this.child}) : super(key: key);
@override
Widget build(BuildContext context) {
return ClipPath(
clipper: Clipper(),
child: child,
);
}
}
Constructors on Abstract Classes in Dart
import 'dart:developer' as devtools show log;
extension Log on Object {
void log() => devtools.log(toString());
}
enum Type { dog, cat }
abstract class CanRun {
final Type type;
const CanRun({required this.type});
}
class Cat extends CanRun {
const Cat() : super(type: Type.cat);
}
class Dog extends CanRun {
const Dog() : super(type: Type.dog);
}
@useResult in Dart
import 'package:meta/meta.dart' show useResult;
class Person {
final String firstName;
final String lastName;
const Person({
required this.firstName,
required this.lastName,
});
@useResult
String fullName() => '$firstName $lastName';
}
void printFullName() {
const Person(
firstName: 'Foo',
lastName: 'Bar',
).fullName();
}
@mustCallSuper in Dart
class Animal {
@mustCallSuper
void run() {}
}
class Dog extends Animal {
@override
void run() {}
}
Object.hash in Dart
class BreadCrumb {
final bool isActive;
final String name;
BreadCrumb({
required this.isActive,
required this.name,
});
BreadCrumb activated() => BreadCrumb(
isActive: true,
name: name,
);
@override
bool operator ==(covariant BreadCrumb other) =>
isActive == other.isActive && name == other.name;
@override
int get hashCode => Object.hash(isActive, name);
}
Expanded Equally in Flutter
import 'package:flutter/material.dart';
void main() {
runApp(
MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
),
debugShowCheckedModeBanner: false,
home: const HomePage(),
),
);
}
extension ExpandEqually on Iterable<Widget> {
Iterable<Widget> expandedEqually() => map(
(w) => Expanded(
flex: 1,
child: w,
),
);
}
class HomePage extends StatelessWidget {
const HomePage({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: const Text('Home Page'),
),
body: Column(
children: [
Row(
mainAxisSize: MainAxisSize.max,
children: [
Container(
height: 200,
color: Colors.yellow,
),
Container(
height: 200,
color: Colors.blue,
),
].expandedEqually().toList(),
)
],
),
);
}
}
Random Iterable Value in Dart
import 'dart:math' as math show Random;
extension RandomElement<T> on Iterable<T> {
T getRandomElement() => elementAt(
math.Random().nextInt(length),
);
}
final colors = [Colors.blue, Colors.red, Colors.brown];
class HomePage extends StatelessWidget {
final color = ValueNotifier<MaterialColor>(
colors.getRandomElement(),
);
HomePage({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: const Text('List.Random in Flutter'),
),
body: ColorPickerButton(color: color),
);
}
}
class ColorPickerButton extends StatelessWidget {
final ValueNotifier<MaterialColor> color;
const ColorPickerButton({
Key? key,
required this.color,
}) : super(key: key);
@override
Widget build(BuildContext context) {
return ValueListenableBuilder<Color>(
valueListenable: color,
builder: (context, value, child) {
return Padding(
padding: const EdgeInsets.all(8.0),
child: CenteredTight(
child: TextButton(
style: TextButton.styleFrom(backgroundColor: value),
onPressed: () {
color.value = colors.getRandomElement();
},
child: const Text(
'Change color',
style: TextStyle(
fontSize: 30,
color: Colors.white,
),
),
),
),
);
},
);
}
}
Hardcoded Strings in Flutter
extension Hardcoded on String {
String get hardcoded => '$this 🧨';
}
class HomePage extends StatelessWidget {
const HomePage({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(
'My hardcoded string'.hardcoded,
),
),
body: Row(
mainAxisAlignment: MainAxisAlignment.center,
children: [
Text('String in body'.hardcoded),
],
),
);
}
}
Manually Scroll in List View in Flutter
// Free Flutter Course 💙 https://linktr.ee/vandadnp
import 'package:scrollable_positioned_list/scrollable_positioned_list.dart';
class HomePage extends StatelessWidget {
final _controller = ItemScrollController();
HomePage({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: const Text('Testing'),
),
body: ScrollablePositionedList.builder(
itemScrollController: _controller,
itemCount: allImages.length + 1,
itemBuilder: (context, index) {
if (index == 0) {
return IndexSelector(
count: allImages.length,
onSelected: (index) {
_controller.scrollTo(
index: index + 1,
duration: const Duration(milliseconds: 370),
);
},
);
} else {
return ImageWithTitle(index: index);
}
},
),
);
}
}
class ImageWithTitle extends StatelessWidget {
final int index;
const ImageWithTitle({
Key? key,
required this.index,
}) : super(key: key);
@override
Widget build(BuildContext context) {
return Column(
children: [
Text(
'Image $index',
style: const TextStyle(fontSize: 30.0),
),
Image.network(allImages.elementAt(index - 1)),
],
);
}
}
typedef OnIndexSelected = void Function(int index);
class IndexSelector extends StatelessWidget {
final int count;
final OnIndexSelected onSelected;
final String prefix;
const IndexSelector({
Key? key,
required this.count,
required this.onSelected,
this.prefix = 'Image',
}) : super(key: key);
@override
Widget build(BuildContext context) {
return SingleChildScrollView(
scrollDirection: Axis.horizontal,
child: Row(
children: Iterable.generate(
count,
(index) => TextButton(
onPressed: () {
onSelected(index);
},
child: Text('$prefix ${index + 1}'),
),
).toList(),
),
);
}
}
const imageUrls = [
'https://bit.ly/3ywI8l6',
'https://bit.ly/36fNNj9',
'https://bit.ly/3jOueGG',
'https://bit.ly/3qYOtDm',
'https://bit.ly/3wt11Ec',
'https://bit.ly/3yvFg7X',
'https://bit.ly/3ywzOla',
'https://bit.ly/3wnASpW',
'https://bit.ly/3jXSDto',
];
AsyncSnapshot to Widget in Flutter
import 'package:flutter/material.dart';
import 'package:flutter_hooks/flutter_hooks.dart';
void main() {
runApp(
MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: const HomePage(),
),
);
}
final future = Future<String>.delayed(
const Duration(seconds: 3),
() => 'Hello world',
);
typedef ResolveToWidget<T> = Widget Function(
ConnectionState connectionState,
AsyncSnapshot<T> snapshot,
);
extension Materialize on AsyncSnapshot {
Widget materialize(ResolveToWidget f) => f(
connectionState,
this,
);
}
class HomePage extends HookWidget {
const HomePage({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: const Text('Hooks'),
),
body: useFuture(future).materialize((connectionState, snapshot) {
switch (connectionState) {
case ConnectionState.done:
return Text(snapshot.data ?? '');
default:
return const CircularProgressIndicator();
}
}),
);
}
}
Breadcrumbs in Flutter
@immutable
class BreadCrumbPath {
final String title;
final bool isActive;
const BreadCrumbPath({
required this.title,
required this.isActive,
});
BreadCrumbPath activated() {
return BreadCrumbPath(
title: title,
isActive: true,
);
}
@override
String toString() => title;
}
class BreatCrumbPathView extends StatelessWidget {
final BreadCrumbPath path;
const BreatCrumbPathView({
Key? key,
required this.path,
}) : super(key: key);
@override
Widget build(BuildContext context) {
final title = path.isActive ? '${path.title} →' : path.title;
return Padding(
padding: const EdgeInsets.all(2.0),
child: Text(
title,
style: TextStyle(
height: 1.0,
fontSize: 20.0,
color: path.isActive ? Colors.blueAccent : Colors.black,
),
),
);
}
}
typedef OnBreadCrumbPathTapped = void Function(BreadCrumbPath path);
class BreadCrumbView extends StatelessWidget {
final OnBreadCrumbPathTapped onTapped;
final Stream<List<BreadCrumbPath>> paths;
const BreadCrumbView({
Key? key,
required this.paths,
required this.onTapped,
}) : super(key: key);
@override
Widget build(BuildContext context) {
return StreamBuilder<List<BreadCrumbPath>>(
stream: paths,
builder: (context, snapshot) {
final List<Widget> views;
switch (snapshot.connectionState) {
case ConnectionState.waiting:
case ConnectionState.active:
final paths = snapshot.data ?? [];
final views = paths
.map(
(path) => GestureDetector(
onTap: () => onTapped(path),
child: BreatCrumbPathView(path: path),
),
)
.toList();
return Wrap(
spacing: 4.0,
children: views,
alignment: WrapAlignment.start,
crossAxisAlignment: WrapCrossAlignment.center,
);
default:
return Wrap();
}
},
);
}
}
class HomePage extends StatefulWidget {
const HomePage({Key? key}) : super(key: key);
@override
State<HomePage> createState() => _HomePageState();
}
class _HomePageState extends State<HomePage> {
List<BreadCrumbPath> _paths = [];
late final TextEditingController _textController;
late final StreamController<List<BreadCrumbPath>> _pathsController;
@override
void initState() {
_pathsController = StreamController<List<BreadCrumbPath>>.broadcast(
onListen: () {
_pathsController.add(_paths);
},
);
_textController = TextEditingController();
super.initState();
}
@override
void dispose() {
_textController.dispose();
_pathsController.close();
super.dispose();
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: const Text('Breadcrumb in Flutter'),
),
body: Padding(
padding: const EdgeInsets.all(16.0),
child: Column(
crossAxisAlignment: CrossAxisAlignment.start,
children: [
BreadCrumbView(
paths: _pathsController.stream,
onTapped: (path) async {
await showBreadCrumbPathTappedDialog(
context,
path,
);
},
),
TextField(
controller: _textController,
textAlign: TextAlign.center,
decoration: const InputDecoration(
hintText: 'Enter a new path here',
),
),
TextButton(
onPressed: () {
_paths = [
..._paths.map((p) => p.activated()),
BreadCrumbPath(
title: _textController.text,
isActive: false,
),
];
_pathsController.add(_paths);
_textController.clear();
},
child: const Center(
child: Text('Add new path'),
),
),
],
),
),
);
}
}
Future<void> showBreadCrumbPathTappedDialog(
BuildContext context,
BreadCrumbPath path,
) {
return showDialog(
context: context,
builder: (context) {
return AlertDialog(
content: Text('You tapped on $path'),
actions: [
TextButton(
onPressed: () {
Navigator.of(context).pop();
},
child: const Text('OK'),
),
],
);
},
);
}
Unique Map Values in Dart
import 'dart:developer' as devtools show log;
extension ContainsDuplicateValues on Map {
bool get containsDuplicateValues =>
{...values}.length != values.length;
}
extension Log on Object {
void log() => devtools.log(toString());
}
const people1 = {
1: 'Foo',
2: 'Bar',
};
const people2 = {
1: 'Foo',
2: 'Foo',
};
void testIt() {
people1.containsDuplicateValues.log(); // false
people2.containsDuplicateValues.log(); // true
}
Smart Quotes/Dashes in Flutter
class HomePage extends StatelessWidget {
const HomePage({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: const Text('Smart Quotes/Dashes in Flutter'),
),
body: const Padding(
padding: EdgeInsets.all(16.0),
child: TextField(
smartQuotesType: SmartQuotesType.disabled,
smartDashesType: SmartDashesType.disabled,
maxLines: null,
),
),
);
}
}
Haptic Feedback in Flutter
class CenteredTight extends StatelessWidget {
final Widget child;
const CenteredTight({
Key? key,
required this.child,
}) : super(key: key);
@override
Widget build(BuildContext context) {
return Row(
mainAxisAlignment: MainAxisAlignment.center,
children: [child],
);
}
}
class FullscreenImage extends StatefulWidget {
final String imageUrl;
const FullscreenImage({Key? key, required this.imageUrl}) : super(key: key);
@override
State<FullscreenImage> createState() => _FullscreenImageState();
}
class _FullscreenImageState extends State<FullscreenImage> {
var shouldDisplayAppbar = false;
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: shouldDisplayAppbar ? AppBar(title: const Text('Image')) : null,
body: GestureDetector(
onTap: () {
setState(() => shouldDisplayAppbar = !shouldDisplayAppbar);
},
child: Image.network(
widget.imageUrl,
alignment: Alignment.center,
width: double.infinity,
height: double.infinity,
fit: BoxFit.cover,
),
),
);
}
}
class HomePage extends StatelessWidget {
const HomePage({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: const Text('Haptic Feedback in Flutter'),
),
body: Padding(
padding: const EdgeInsets.all(16.0),
child: CenteredTight(
child: FractionallySizedBox(
heightFactor: 0.7,
child: GestureDetector(
onLongPress: () async {
await HapticFeedback.lightImpact();
Navigator.of(context).push(
MaterialPageRoute(
builder: (context) {
return const FullscreenImage(
imageUrl: imageUrl,
);
},
),
);
},
child: Image.network(imageUrl),
),
),
),
),
);
}
}
Localization Delegates in Flutter
import 'package:flutter_gen/gen_l10n/app_localizations.dart';
void main() {
WidgetsFlutterBinding.ensureInitialized();
runApp(
MaterialApp(
localizationsDelegates: AppLocalizations.localizationsDelegates,
supportedLocales: AppLocalizations.supportedLocales,
title: 'Flutter Demo',
debugShowCheckedModeBanner: false,
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: BlocProvider<AuthBloc>(
create: (context) => AuthBloc(FirebaseAuthProvider()),
child: const HomePage(),
),
routes: {
createOrUpdateNoteRoute: (context) => const CreateUpdateNoteView(),
},
),
);
}
Extending Functions in Dart
import 'dart:developer' as devtools show log;
extension ToTextButton on VoidCallback {
TextButton toTextButton(String title) {
return TextButton(
onPressed: this,
child: Text(title),
);
}
}
class HomePage extends StatelessWidget {
const HomePage({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: const Text('Extensions in Flutter'),
),
body: () {
devtools.log('I am pressed');
}.toTextButton('Press me'),
);
}
}
Paginated ListView in Flutter
@immutable
class Season {
final String name;
final String imageUrl;
const Season({required this.name, required this.imageUrl});
const Season.spring()
: name = 'Spring',
imageUrl = 'https://cnn.it/3xu58Ap';
const Season.summer()
: name = 'Summer',
imageUrl = 'https://bit.ly/2VcCSow';
const Season.autumn()
: name = 'Autumn',
imageUrl = 'https://bit.ly/3A3zStC';
const Season.winter()
: name = 'Winter',
imageUrl = 'https://bit.ly/2TNY7wi';
}
const allSeasons = [
Season.spring(),
Season.summer(),
Season.autumn(),
Season.winter()
];
class HomePage extends StatelessWidget {
const HomePage({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
final width = MediaQuery.of(context).size.width;
final height = width / (16.0 / 9.0);
return Scaffold(
appBar: AppBar(
title: const Text('PageScrollPhysics in Flutter'),
),
body: SizedBox(
width: width,
height: height,
child: ListView(
shrinkWrap: true,
scrollDirection: Axis.horizontal,
physics: const PageScrollPhysics(),
clipBehavior: Clip.antiAlias,
children: allSeasons.map((season) {
return SizedBox(
width: width,
height: height,
child: Image.network(
season.imageUrl,
height: height,
fit: BoxFit.cover,
),
);
}).toList(),
),
),
);
}
}
Immutable Classes in Dart
import 'package:flutter/foundation.dart' show immutable;
@immutable
abstract class Animal {
final String name;
const Animal(this.name);
}
class Cat extends Animal {
const Cat() : super('Cindy Clawford');
}
class Dog extends Animal {
int age;
Dog()
: age = 0,
super('Bark Twain');
}
Card Widget in Flutter
class HomePage extends StatelessWidget {
const HomePage({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: const Text('Card in Flutter'),
),
body: Image.network(
'https://bit.ly/36fNNj9',
frameBuilder: (context, child, frame, wasSynchronouslyLoaded) {
return Card(
child: child,
clipBehavior: Clip.antiAlias,
);
},
loadingBuilder: (context, child, loadingProgress) {
final totalBytes = loadingProgress?.expectedTotalBytes;
final bytesLoaded = loadingProgress?.cumulativeBytesLoaded;
if (totalBytes != null && bytesLoaded != null) {
return Row(
mainAxisAlignment: MainAxisAlignment.center,
children: const [CircularProgressIndicator()],
);
} else {
return child;
}
},
),
);
}
}
List Equality Ignoring Ordering in Dart
@immutable
class Person {
final String name;
const Person(this.name);
@override
bool operator ==(covariant Person other) => other.name == name;
@override
int get hashCode => name.hashCode;
@override
String toString() => name;
}
const people1 = [Person('Foo'), Person('Bar'), Person('Baz')];
const people2 = [Person('Foo'), Person('Bar'), Person('Baz')];
const people3 = [Person('Bar'), Person('Bar'), Person('Baz')];
const people4 = [Person('Bar'), Person('Baz')];
extension IsEqualToIgnoringOrdering<T> on List<T> {
bool isEqualToIgnoringOrdering(List<T> other) =>
length == other.length &&
{...this}.intersection({...other}).length == length;
}
void testIt() {
assert(people1.isEqualToIgnoringOrdering(people2));
assert(!people1.isEqualToIgnoringOrdering(people3));
assert(!people2.isEqualToIgnoringOrdering(people3));
assert(!people3.isEqualToIgnoringOrdering(people4));
}
Shorten GitHub URLs in Dart
// Want to support my work 🤝? https://buymeacoffee.com/vandad
import 'dart:developer' as devtools show log;
import 'dart:convert' show utf8;
Future<Uri> shortenGitHubUrl(String longUrl) =>
HttpClient().postUrl(Uri.parse('https://git.io/')).then((req) {
req.add(utf8.encode('url=$longUrl'));
return req.close();
}).then(
(resp) async {
try {
final location = resp.headers[HttpHeaders.locationHeader]?.first;
if (location != null) {
return Uri.parse(location);
} else {
throw 'No location was specified';
}
} catch (e) {
return Uri.parse(longUrl);
}
},
);
void testIt() async {
final uri = await shortenGitHubUrl(
'https://github.com/vandadnp/flutter-tips-and-tricks');
devtools.log(uri.toString());
// logs https://git.io/JS5Fm
}
Time Picker in Flutter
class HomePage extends StatelessWidget {
final timeOfDay = ValueNotifier<TimeOfDay?>(null);
HomePage({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
return ValueListenableBuilder(
valueListenable: timeOfDay,
builder: (context, value, child) {
final title = timeOfDay.value?.toString() ?? 'Time Picker in Flutter';
return Scaffold(
appBar: AppBar(title: Text(title)),
body: Center(
child: TextButton(
onPressed: () async {
timeOfDay.value = await showTimePicker(
context: context,
initialTime: TimeOfDay.now(),
initialEntryMode: TimePickerEntryMode.input,
);
},
child: const Text('Please Pick a time'),
),
),
);
},
);
}
}
Throttled Print in Flutter
Stream<String> getStream() => Stream.periodic(
const Duration(milliseconds: 100),
(e) => DateTime.now().toString(),
);
void testIt() async {
await for (final now in getStream()) {
debugPrintThrottled(now);
}
}
Map Equality in Dart
typedef Name = String;
typedef Age = int;
const Map<Name, Age> people1 = {
'foo': 20,
'bar': 30,
'baz': 40,
};
const Map<Name, Age> people2 = {
'baz': 40,
'foo': 20,
'bar': 30,
};
void testIt() {
assert(mapEquals(people1, people2));
}
Unique Maps in Dart
import 'dart:developer' as devtools show log;
typedef Name = String;
typedef Age = int;
const Map<Name, Age> people = {
'foo': 20,
'bar': 30,
'baz': 20,
};
extension Unique<K, V> on Map<K, V> {
Map<K, V> unique() {
Map<K, V> result = {};
for (final value in {...values}) {
final firstKey = keys.firstWhereOrNull((key) => this[key] == value);
if (firstKey != null) {
result[firstKey] = value;
}
}
return result;
}
}
void testIt() {
final uniques = people.unique();
devtools.log(uniques.toString());
// prints: {foo: 20, bar: 30}
}
Raw Auto Complete in Flutter
const emailProviders = [
'gmail.com',
'hotmail.com',
'yahoo.com',
];
const icons = [
'https://bit.ly/3HsvvvB',
'https://bit.ly/3n6GW4L',
'https://bit.ly/3zf2RLy',
];
class EmailTextField extends StatefulWidget {
const EmailTextField({Key? key}) : super(key: key);
@override
State<EmailTextField> createState() => _EmailTextFieldState();
}
class _EmailTextFieldState extends State<EmailTextField> {
late final TextEditingController _controller;
late final FocusNode _focus;
@override
Widget build(BuildContext context) {
return RawAutocomplete<String>(
textEditingController: _controller,
focusNode: _focus,
fieldViewBuilder: (_, controller, focusNode, onSubmitted) {
return TextFormField(
controller: controller,
focusNode: focusNode,
onFieldSubmitted: (value) {
onSubmitted();
},
);
},
optionsBuilder: (textEditingValue) {
final lastChar = textEditingValue.text.characters.last;
if (lastChar == '@') {
return emailProviders;
} else {
return [];
}
},
optionsViewBuilder: (context, onSelected, options) {
return OptionsList(
onSelected: onSelected,
options: options,
controller: _controller,
);
},
);
}
@override
void initState() {
_controller = TextEditingController();
_focus = FocusNode();
super.initState();
}
@override
void dispose() {
_focus.dispose();
_controller.dispose();
super.dispose();
}
}
class OptionsList extends StatelessWidget {
final Iterable<String> options;
final AutocompleteOnSelected<String> onSelected;
final TextEditingController controller;
const OptionsList({
Key? key,
required this.onSelected,
required this.options,
required this.controller,
}) : super(key: key);
@override
Widget build(BuildContext context) {
return Align(
alignment: Alignment.topLeft,
child: Material(
child: SizedBox(
height: 150,
child: ListView.builder(
padding: const EdgeInsets.all(0.0),
itemCount: options.length,
itemBuilder: (context, index) {
final option = options.elementAt(index);
return GestureDetector(
onTap: () => onSelected(controller.text + option),
child: ListTile(
horizontalTitleGap: 2.0,
leading: Image.network(
icons[index],
width: 24,
height: 24,
),
title: Text(option),
),
);
},
),
),
),
);
}
}
class HomePage extends StatefulWidget {
const HomePage({Key? key}) : super(key: key);
@override
_HomePageState createState() => _HomePageState();
}
class _HomePageState extends State<HomePage> {
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: const Text('Raw Auto Complete in Flutter'),
),
body: const Padding(
padding: EdgeInsets.all(16.0),
child: EmailTextField(),
),
);
}
}
Title on Object in Dart
import 'dart:developer' as devtools show log;
extension CapTitle on Object {
String get capitalizedTitle {
String str;
if (this is Enum) {
str = (this as Enum).name;
} else {
str = toString();
}
return str[0].toUpperCase() + str.substring(1);
}
}
enum EmailProviders { gmail, yahoo, hotmail }
void testIt() {
EmailProviders.values.map((p) => p.capitalizedTitle).forEach(devtools.log);
// prints these:
// Gmail
// Yahoo
// Hotmail
}
Compute in Flutter
import 'dart:developer' as devtools show log;
import 'dart:convert' show utf8, json;
@immutable
class Person {
final String name;
final int age;
const Person(this.name, this.age);
Person.fromJson(Map<String, dynamic> json)
: name = json["name"] as String,
age = json["age"] as int;
}
Future<Iterable<Person>> downloadAndParsePersons(Uri uri) => HttpClient()
.getUrl(uri)
.then((req) => req.close())
.then((response) => response.transform(utf8.decoder).join())
.then((jsonString) => json.decode(jsonString) as List<dynamic>)
.then((json) => json.map((map) => Person.fromJson(map)));
void testIt() async {
final persons = await compute(
downloadAndParsePersons,
Uri.parse('https://bit.ly/3Jjcw8R'),
);
devtools.log(persons.toString());
}
Filter on Map in Dart
import 'dart:developer' as devtools show log;
typedef Name = String;
typedef Age = int;
extension Filter<K, V> on Map<K, V> {
Iterable<MapEntry<K, V>> filter(
bool Function(MapEntry<K, V> entry) f,
) sync* {
for (final entry in entries) {
if (f(entry)) {
yield entry;
}
}
}
}
const Map<Name, Age> people = {
'foo': 20,
'bar': 31,
'baz': 25,
'qux': 32,
};
void testIt() async {
final peopleOver30 = people.filter((e) => e.value > 30);
devtools.log(peopleOver30.toString());
// ☝🏻 prints (MapEntry(bar: 31), MapEntry(qux: 32))
}
Type Alias in Dart
const Map<String, int> people1 = {
'foo': 20,
'bar': 30,
'baz': 25,
};
typedef Age = int;
const Map<String, Age> people2 = {
'foo': 20,
'bar': 30,
'baz': 25,
};
ValueNotifier in Flutter
class DynamicToolTipTextField extends StatelessWidget {
final TextInputType? keyboardType;
final ValueNotifier<String?> hint;
final TextEditingController controller;
const DynamicToolTipTextField({
Key? key,
required this.hint,
required this.controller,
this.keyboardType,
}) : super(key: key);
@override
Widget build(BuildContext context) {
return ValueListenableBuilder(
valueListenable: hint,
builder: (context, value, child) {
return TextField(
keyboardType: keyboardType,
controller: controller,
decoration: InputDecoration(
hintText: value as String?,
),
);
},
);
}
}
class HomePage extends StatefulWidget {
const HomePage({Key? key}) : super(key: key);
@override
State<HomePage> createState() => _HomePageState();
}
@immutable
abstract class HasText {
String get text;
}
enum Hint { pleaseEnterYourEmail, youForgotToEnterYourEmail }
extension GetText on Hint {
String get text {
switch (this) {
case Hint.pleaseEnterYourEmail:
return 'Please enter your email';
case Hint.youForgotToEnterYourEmail:
return 'You forgot to enter your email';
}
}
}
class _HomePageState extends State<HomePage> {
late final ValueNotifier<String?> _hint;
late final TextEditingController _controller;
@override
void initState() {
_hint = ValueNotifier<String?>(Hint.pleaseEnterYourEmail.text);
_controller = TextEditingController();
super.initState();
}
@override
void dispose() {
_hint.dispose();
_controller.dispose();
super.dispose();
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: const Text('ValueNotifier in Flutter'),
),
body: Padding(
padding: const EdgeInsets.all(8.0),
child: Column(
children: [
DynamicToolTipTextField(
hint: _hint,
controller: _controller,
keyboardType: TextInputType.emailAddress,
),
TextButton(
onPressed: () async {
final email = _controller.text;
if (email.trim().isEmpty) {
_hint.value = Hint.youForgotToEnterYourEmail.text;
await Future.delayed(const Duration(seconds: 2));
_hint.value = Hint.pleaseEnterYourEmail.text;
}
},
child: const Text('Log in'),
)
],
),
),
);
}
}
Object to Integer in Dart
enum ToIntStrategy { round, floor, ceil }
typedef ToIntOnErrorHandler = int Function(Object e);
extension ToInt on Object {
int toInteger({
ToIntStrategy strategy = ToIntStrategy.round,
ToIntOnErrorHandler? onError,
}) {
try {
final doubleValue = double.parse(toString());
switch (strategy) {
case ToIntStrategy.round:
return doubleValue.round();
case ToIntStrategy.floor:
return doubleValue.floor();
case ToIntStrategy.ceil:
return doubleValue.ceil();
}
} catch (e) {
if (onError != null) {
return onError(e);
} else {
return -1;
}
}
}
}
void testIt() {
assert('xyz'.toInteger(onError: (_) => 100) == 100);
assert(1.5.toInteger() == 2);
assert(1.6.toInteger() == 2);
assert('1.2'.toInteger(strategy: ToIntStrategy.floor) == 1);
assert('1.2'.toInteger(strategy: ToIntStrategy.ceil) == 2);
assert('1.5'.toInteger(strategy: ToIntStrategy.round) == 2);
}
Image Opacity in Flutter
class HomePage extends StatefulWidget {
const HomePage({Key? key}) : super(key: key);
@override
State<HomePage> createState() => _HomePageState();
}
class _HomePageState extends State<HomePage>
with SingleTickerProviderStateMixin {
late final AnimationController _controller;
late final Animation<double> _opacity;
@override
void initState() {
_controller = AnimationController(
vsync: this,
duration: const Duration(seconds: 1),
);
_opacity = Tween(begin: 0.0, end: 1.0).animate(_controller);
super.initState();
}
@override
Widget build(BuildContext context) {
return Scaffold(
body: Column(
children: [
Image.network(
'https://bit.ly/3ywI8l6',
opacity: _opacity,
),
Slider(
value: _controller.value,
onChanged: (value) {
setState(() => _controller.value = value);
},
),
],
),
);
}
@override
void dispose() {
_controller.dispose();
super.dispose();
}
}
Covariant in Dart
// Want to support my work 🤝? https://buymeacoffee.com/vandad
class Person {
final String name;
const Person(this.name);
@override
bool operator ==(Object other) {
if (other is! Person) throw ArgumentError('Was expecting a person');
return other.name == name;
}
@override
int get hashCode => name.hashCode;
}
class Person {
final String name;
const Person(this.name);
@override
bool operator ==(covariant Person other) => other.name == name;
@override
int get hashCode => name.hashCode;
}
Custom Errors in Streams in Dart
class Either<V, E extends Exception> {
final V? value;
final E? error;
const Either({this.value, this.error}) : assert((value ?? error) != null);
bool get isError => error != null;
bool get isValue => value != null;
@override
String toString() {
if (value != null) {
return "Value: $value";
} else if (error != null) {
return "Error: $error";
} else {
return 'Unknown state';
}
}
}
class DateTimeException implements Exception {
final String reason;
const DateTimeException({required this.reason});
}
Stream<Either<DateTime, DateTimeException>> getDateTime() async* {
var index = 0;
while (true) {
if (index % 2 == 0) {
yield Either(value: DateTime.now());
} else {
yield const Either(
error: DateTimeException(reason: 'Something is wrong!'),
);
}
index += 1;
}
}
void testIt() async {
await for (final value in getDateTime()) {
dev.log(value.toString());
}
}
Shake Animation in Flutter
class HomePage extends StatefulWidget {
const HomePage({Key? key}) : super(key: key);
@override
State<HomePage> createState() => _HomePageState();
}
const animationWidth = 10.0;
class _HomePageState extends State<HomePage>
with SingleTickerProviderStateMixin {
late final TextEditingController _textController;
late final AnimationController _animationController;
late final Animation<double> _offsetAnim;
final defaultHintText = 'Please enter your email here 😊';
var _hintText = '';
@override
void initState() {
_hintText = defaultHintText;
_textController = TextEditingController();
_animationController = AnimationController(
duration: const Duration(milliseconds: 370),
vsync: this,
);
_offsetAnim = Tween(
begin: 0.0,
end: animationWidth,
).chain(CurveTween(curve: Curves.elasticIn)).animate(
_animationController,
)..addStatusListener(
(status) {
if (status == AnimationStatus.completed) {
_animationController.reverse();
}
},
);
super.initState();
}
@override
void dispose() {
_textController.dispose();
_animationController.dispose();
super.dispose();
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: const Text('Shake Animation in Flutter'),
),
body: Padding(
padding: const EdgeInsets.all(8.0),
child: Column(
children: [
AnimatedBuilder(
animation: _offsetAnim,
builder: (context, child) {
return Container(
margin: const EdgeInsets.symmetric(
horizontal: animationWidth,
),
padding: EdgeInsets.only(
left: _offsetAnim.value + animationWidth,
right: animationWidth - _offsetAnim.value,
),
child: TextField(
controller: _textController,
keyboardType: TextInputType.emailAddress,
decoration: InputDecoration(
hintText: _hintText,
),
),
);
},
),
TextButton(
onPressed: () async {
if (_textController.text.isEmpty) {
setState(() {
_hintText = 'You forgot to enter your email 🥲';
_animationController.forward(from: 0.0);
});
await Future.delayed(const Duration(seconds: 3));
setState(() {
_hintText = defaultHintText;
});
}
},
child: const Text('Login'))
],
),
),
);
}
}
Throw Enums in Dart
import 'dart:developer' as dev show log;
enum Exceptions { invalidUserName, invalidPassword }
void thisMethodThrows() {
throw Exceptions.invalidPassword;
}
void testIt() {
try {
thisMethodThrows();
} on Exceptions catch (e) {
switch (e) {
case (Exceptions.invalidUserName):
dev.log("Invalid user name");
break;
case (Exceptions.invalidPassword):
dev.log("Invalid password");
break;
}
}
}
Future Error Test in Flutter
import 'dart:developer' as dev show log;
@immutable
abstract class UserException implements Exception {}
class InvalidUserNameException extends UserException {}
class InvalidUserAgeException extends UserException {}
@immutable
class User {
final String name;
final int age;
User({required this.name, required this.age}) {
if (!name.contains(RegExp(r'^[a-z ]+$'))) {
throw InvalidUserNameException();
} else if (age < 0 || age > 130) {
throw InvalidUserAgeException();
}
}
const User.anonymous()
: name = 'Anonymous User',
age = 0;
}
Future<User> getAsyncUser() => Future.delayed(
const Duration(seconds: 1),
() => User(name: 'Foo', age: 20),
);
void testIt() async {
final user = await getAsyncUser()
.catchError(
handleInvalidUsernameException,
test: (e) => e is InvalidUserNameException,
)
.catchError(
handleInvalidAgeException,
test: (e) => e is InvalidUserAgeException,
);
dev.log(user.toString());
}
User handleInvalidUsernameException(Object? e) {
dev.log(e.toString());
return const User.anonymous();
}
User handleInvalidAgeException(Object? e) {
dev.log(e.toString());
return const User.anonymous();
}
Generic URL Retrieval in Dart
import 'dart:developer' as dev show log;
typedef StatusCodeResultBuilder<T> = Future<T> Function(
int statusCode,
HttpClientResponse response,
);
extension Get on Uri {
Future<T?> getBody<T>({
StatusCodeResultBuilder<T>? statusBuilder,
T Function(Object error)? onNetworkError,
}) async {
try {
final apiCall = await HttpClient().getUrl(this);
final response = await apiCall.close();
final builder = statusBuilder;
if (builder == null) {
final data = await response.transform(convert.utf8.decoder).join();
if (data is T) {
return data as T?;
} else {
return null;
}
} else {
final result = await builder(response.statusCode, response);
return result;
}
} catch (e) {
if (onNetworkError != null) {
return onNetworkError(e);
} else {
return null;
}
}
}
}
extension ToUri on String {
Uri toUri() => Uri.parse(this);
}
const url = 'https://bit.ly/3EKWcLa';
void testIt() async {
final json = await url.toUri().getBody<String>(
statusBuilder: (statusCode, response) async {
if (statusCode == 200) {
return await response.transform(convert.utf8.decoder).join();
} else {
return "{'error': 'Unexpected status code $statusCode'}";
}
},
onNetworkError: (error) {
return "{'error': 'Got network error'}";
},
);
if (json != null) {
dev.log(json);
}
}
Custom Error Widget in Flutter
class MyErrorWidget extends StatelessWidget {
final String text;
const MyErrorWidget({Key? key, required this.text}) : super(key: key);
@override
Widget build(BuildContext context) {
return Scaffold(
body: SizedBox(
width: MediaQuery.of(context).size.width,
child: Padding(
padding: const EdgeInsets.all(16.0),
child: Column(
mainAxisAlignment: MainAxisAlignment.start,
children: [
Image.network('https://bit.ly/3gHlTCU'),
Text(
text,
textAlign: TextAlign.center,
style: const TextStyle(
color: Colors.red,
),
),
],
),
),
),
);
}
}
void main() {
ErrorWidget.builder = (FlutterErrorDetails details) {
bool isInDebugMode = false;
assert(() {
isInDebugMode = true;
return true;
}());
final message = details.exception.toString();
if (isInDebugMode) {
return MyErrorWidget(text: message);
} else {
return Text(
message,
textAlign: TextAlign.center,
);
}
};
runApp(
const MaterialApp(
home: HomePage(),
debugShowCheckedModeBanner: false,
),
);
}
class HomePage extends StatelessWidget {
const HomePage({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: const Text('Error Widget in Flutter'),
),
body: Builder(
builder: (context) {
throw Exception(
'Here is an exception that is caught by our custom Error Widget in Flutter');
},
),
);
}
}
Handle Multiple Future Errors in Dart
import 'dart:developer' as dev show log;
Future<Iterable<T>> waitOn<T>(
Iterable<Future<T>> futures,
Function onError,
) async {
List<T> result = [];
for (final future in futures) {
final value = await future.catchError(onError);
result.add(value);
}
return result;
}
void testIt() async {
final f1 = Future.error('First Error');
final f2 = Future.delayed(const Duration(seconds: 2), () => 10);
final f3 = Future.error('Second error');
final f4 = Future.delayed(const Duration(seconds: 2), () => 'Hello world');
final result = await waitOn([f1, f2, f3, f4], (error) => -1);
dev.log(result.toString()); // [-1, 10, -1, Hello world]
}
Future Error Handling in Dart
import 'dart:developer' as dev show log;
extension OnError<T> on Future<T> {
Future<T> onErrorJustReturn(T value) => catchError((_) => value);
}
Future<bool> isUserRegistered({required String email}) => HttpClient()
.postUrl(Uri.parse('https://website'))
.then((req) {
req.headers.add('email', email);
return req.close();
})
.then((resp) => resp.statusCode == 200)
.onErrorJustReturn(false);
void testIt() async {
final isFooRegistered = await isUserRegistered(email: 'foo@flutter.com');
dev.log(isFooRegistered.toString());
}
String to Toast in Flutter
extension Toast on String {
Future<void> showAsToast(BuildContext context,
{required Duration duration}) async {
final scaffold = ScaffoldMessenger.of(context);
final controller = scaffold.showSnackBar(
SnackBar(
content: Text(this),
backgroundColor: const Color(0xFF24283b),
behavior: SnackBarBehavior.floating,
elevation: 2.0,
shape: RoundedRectangleBorder(
borderRadius: BorderRadius.circular(10),
),
),
);
await Future.delayed(duration);
controller.close();
}
}
class HomePage extends StatefulWidget {
const HomePage({Key? key}) : super(key: key);
@override
_HomePageState createState() => _HomePageState();
}
class _HomePageState extends State<HomePage> {
@override
Widget build(BuildContext context) {
return Scaffold(
body: Center(
child: TextButton(
onPressed: () => 'Hello, World!'.showAsToast(
context,
duration: const Duration(seconds: 2),
),
child: const Text('Show the snackbar'),
),
),
);
}
}
Waiting in Dart
Future<void> wait(Duration d) async {
await Future.delayed(d);
}
extension Wait on int {
Future<void> get seconds => wait(Duration(seconds: this));
Future<void> get minutes => wait(Duration(minutes: this));
}
void testIt() async {
await 2.seconds;
'After 2 seconds'.log();
await 3.minutes;
'After 3 minutes'.log();
}
extension Log on Object {
void log() {
dev.log(toString());
}
}
Loading Dialog in Flutter
typedef CloseDialog = void Function();
CloseDialog showLoadingScreen({
required BuildContext context,
required String text,
}) {
final dialog = AlertDialog(
content: Column(
mainAxisSize: MainAxisSize.min,
children: [
const CircularProgressIndicator(),
const SizedBox(height: 10),
Text(text),
],
),
);
showDialog(
context: context,
barrierDismissible: false,
builder: (_) => dialog,
);
return () => Navigator.of(context).pop();
}
void testIt(BuildContext context) async {
final closeDialog = showLoadingScreen(
context: context,
text: 'Loading data...',
);
await Future.delayed(const Duration(seconds: 2));
closeDialog();
}
Compact Map on Map<K,V> in Dart
const foo = 'foo';
const bar = 'bar';
const baz = 'baz';
const namesAndAges = {
foo: 20,
bar: 25,
baz: 18,
};
const acceptedNames = [
foo,
bar,
];
void testIt() {
final acceptedAges = namesAndAges.compactMap(
(e) => acceptedNames.contains(e.key) ? e.value : null,
);
acceptedAges.log(); // [20, 25]
}
extension CompactMap<T, E> on Map<T, E> {
Iterable<V> compactMap<V>(V? Function(MapEntry<T, E>) f) sync* {
for (final entry in entries) {
final extracted = f(entry);
if (extracted != null) {
yield extracted;
}
}
}
}
Query Parameters in Dart
import 'dart:developer' as devtools show log;
const host = 'freecurrencyapi.net';
const path = '/api/v2/latest';
const apiKey = 'YOUR_API_KEY';
const baseCurrency = 'sek';
const params = {
'apiKey': apiKey,
'base_currency': 'sek',
};
void insteadOfThis() {
const url = 'https://$host$path?apiKey=$apiKey&base_currency=$baseCurrency';
url.log();
}
void doThis() {
final url = Uri.https(host, path, params);
url.log();
}
extension Log on Object {
void log() {
devtools.log(toString());
}
}
Multiple Gradients in Container in Flutter
typedef GradientContainersBuilder = Map<LinearGradient, Widget?> Function();
class GradientContainers extends StatelessWidget {
final GradientContainersBuilder builder;
const GradientContainers({
Key? key,
required this.builder,
}) : super(key: key);
@override
Widget build(BuildContext context) {
return Stack(
children: builder().entries.map((mapEntry) {
final gradient = mapEntry.key;
final widget = mapEntry.value;
return GradientContainer(
gradient: gradient,
child: widget,
);
}).toList(),
);
}
}
class GradientContainer extends StatelessWidget {
final LinearGradient gradient;
final Widget? child;
const GradientContainer({Key? key, required this.gradient, this.child})
: super(key: key);
@override
Widget build(BuildContext context) {
return Positioned.fill(
child: Container(
decoration: BoxDecoration(
gradient: gradient,
),
child: child,
),
);
}
}
class HomePage extends StatelessWidget {
const HomePage({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
return Scaffold(
body: GradientContainers(
builder: () => {
topLeftToBottomRightGradient: null,
rightToLeftGradient: null,
leftToRightGradinet: null,
bottomRightGradient: Image.network('https://bit.ly/3otHHog'),
},
),
);
}
}
const transparent = Color(0x00FFFFFF);
const topLeftToBottomRightGradient = LinearGradient(
begin: Alignment.topLeft,
end: Alignment.bottomRight,
colors: [
Color(0xff2ac3de),
transparent,
],
);
const bottomRightGradient = LinearGradient(
begin: Alignment.bottomRight,
end: Alignment.topLeft,
colors: [
Color(0xffbb9af7),
transparent,
],
);
const rightToLeftGradient = LinearGradient(
begin: Alignment.centerRight,
end: Alignment.centerLeft,
colors: [
Color(0xff9ece6a),
transparent,
],
);
const leftToRightGradinet = LinearGradient(
begin: Alignment.centerLeft,
end: Alignment.centerRight,
colors: [
Color(0xff7dcfff),
transparent,
],
);
void main() {
runApp(
const MaterialApp(
home: HomePage(),
debugShowCheckedModeBanner: false,
),
);
}
Filter on Stream<List<T>> in Dart
import 'dart:developer' as devtools show log;
extension Filter<T> on Stream<List<T>> {
Stream<List<T>> filter(bool Function(T) where) =>
map((items) => items.where(where).toList());
}
final Stream<List<int>> allNumbers = Stream.periodic(
const Duration(seconds: 1),
(value) => [for (var i = 0; i < value; i++) i],
);
bool isEven(num value) => value % 2 == 0;
bool isOdd(num value) => value % 2 != 0;
extension EvenOdd<E extends num> on Stream<List<E>> {
Stream<List<E>> get evenNumbers => filter(isEven);
Stream<List<E>> get oddNumbers => filter(isOdd);
}
void readEvenNumbers() async {
await for (final evenNumber in allNumbers.evenNumbers) {
devtools.log('All even numbers: $evenNumber');
}
}
void readOddNumbers() async {
await for (final oddNumber in allNumbers.oddNumbers) {
devtools.log('All odd numbers: $oddNumber');
}
}
Generic Route Arguments in Flutter
extension GetArgument on BuildContext {
T? getArgument<T>() {
final modalRoute = ModalRoute.of(this);
if (modalRoute != null) {
final args = modalRoute.settings.arguments;
if (args != null && args is T) {
return args as T;
}
}
return null;
}
}
Generic Dialog in Flutter
typedef DialogOptionBuilder<T> = Map<String, T> Function();
Future<T?> showGenericDialog<T>({
required BuildContext context,
required String title,
required String content,
required DialogOptionBuilder optionsBuilder,
}) {
final options = optionsBuilder();
return showDialog<T>(
context: context,
builder: (context) {
return AlertDialog(
title: Text(title),
content: Text(content),
actions: options.keys.map(
(optionTitle) {
final T value = options[optionTitle];
return TextButton(
onPressed: () {
Navigator.of(context).pop(value);
},
child: Text(optionTitle),
);
},
).toList(),
);
},
);
}
Future<bool> showLogOutDialog(BuildContext context) {
return showGenericDialog<bool>(
context: context,
title: 'Log out',
content: 'Are you sure you want to log out?',
optionsBuilder: () => {
'Cancel': false,
'Log out': true,
},
).then(
(value) => value ?? false,
);
}
GitHub API in Flutter
import 'dart:io' show HttpHeaders, HttpClient;
import 'package:flutter/foundation.dart';
import 'package:flutter/material.dart';
import 'dart:convert' show utf8, json;
class HomePage extends StatefulWidget {
const HomePage({Key? key}) : super(key: key);
@override
_HomePageState createState() => _HomePageState();
}
Future<Iterable<GithubUser>> getGithubFollowers(String accessToken) =>
HttpClient()
.getUrl(Uri.parse('https://api.github.com/user/followers'))
.then((req) {
req.headers
..set(HttpHeaders.authorizationHeader, 'Bearer $accessToken')
..set(HttpHeaders.contentTypeHeader, 'application/json');
return req.close();
})
.then((resp) => resp.transform(utf8.decoder).join())
.then((jsonStr) => json.decode(jsonStr) as List<dynamic>)
.then(
(jsonArray) => jsonArray.compactMap((element) {
if (element is Map<String, dynamic>) {
return element;
} else {
return null;
}
}),
)
.then(
(listOfMaps) => listOfMaps.map(
(map) => GithubUser.fromJson(map),
),
);
class GithubUser {
final String username;
final String avatarUrl;
GithubUser.fromJson(Map<String, dynamic> json)
: username = json['login'] as String,
avatarUrl = json['avatar_url'] as String;
}
extension CompactMap<T> on List<T> {
List<E> compactMap<E>(E? Function(T element) f) {
Iterable<E> imp(E? Function(T element) f) sync* {
for (final value in this) {
final mapped = f(value);
if (mapped != null) {
yield mapped;
}
}
}
return imp(f).toList();
}
}
const token = 'PUT_YOUR_TOKEN_HERE';
class _HomePageState extends State<HomePage> {
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: const Text('GitHub API in Flutter'),
),
body: FutureBuilder(
future: getGithubFollowers(token),
builder: (context, snapshot) {
switch (snapshot.connectionState) {
case ConnectionState.done:
final users = (snapshot.data as Iterable<GithubUser>).toList();
return ListView.builder(
itemCount: users.length,
itemBuilder: (context, index) {
final user = users[index];
return ListTile(
title: Text(user.username),
leading: CircularAvatar(url: user.avatarUrl),
);
},
);
default:
return const CircularProgressIndicator();
}
},
),
);
}
}
void main() {
runApp(
const MaterialApp(
home: HomePage(),
debugShowCheckedModeBanner: false,
),
);
}
ChangeNotifier in Flutter
import 'package:provider/provider.dart';
import 'package:flutter/foundation.dart';
import 'package:flutter/material.dart';
const allImages = [
'https://bit.ly/3ywI8l6',
'https://bit.ly/36fNNj9',
'https://bit.ly/3jOueGG',
'https://bit.ly/3qYOtDm',
'https://bit.ly/3wt11Ec',
'https://bit.ly/3yvFg7X',
'https://bit.ly/3ywzOla',
'https://bit.ly/3wnASpW',
'https://bit.ly/3jXSDto',
];
class HomePage extends StatefulWidget {
const HomePage({Key? key}) : super(key: key);
@override
State<HomePage> createState() => _HomePageState();
}
class ImageData {
final Uint8List imageData;
const ImageData(this.imageData);
}
class Images extends ChangeNotifier {
final List<ImageData> _items = [];
var _isLoading = false;
bool get isLoading => _isLoading;
UnmodifiableListView<ImageData> get items => UnmodifiableListView(_items);
void loadNextImage() async {
if (_items.length < allImages.length) {
// time to load more
_isLoading = true;
notifyListeners();
final imageUrl = allImages[_items.length];
final networkAsset = NetworkAssetBundle(Uri.parse(imageUrl));
final loaded = await networkAsset.load(imageUrl);
final bytes = loaded.buffer.asUint8List();
final imageData = ImageData(bytes);
_items.insert(0, imageData);
_isLoading = false;
notifyListeners();
} else {
if (isLoading) {
_isLoading = false;
notifyListeners();
}
}
}
}
class _HomePageState extends State<HomePage> {
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: const Text('ChangeNotifier in Flutter'),
actions: [
Consumer<Images>(
builder: (context, value, child) {
return IconButton(
onPressed: () {
value.loadNextImage();
},
icon: const Icon(Icons.add_box_outlined),
);
},
)
],
),
body: Padding(
padding: const EdgeInsets.all(16.0),
child: Consumer<Images>(
builder: (context, value, child) {
final images = value.items;
final isLoading = value.isLoading;
return ListView.builder(
itemBuilder: (context, index) {
if (index == 0 && isLoading) {
return Center(
child: Column(
children: const [
CircularProgressIndicator(),
SizedBox(height: 16.0),
],
),
);
} else {
final imageIndex = isLoading ? index - 1 : index;
final imageData = images[imageIndex].imageData;
return Column(
children: [
RoundedImageWithShadow(imageData: imageData),
const SizedBox(height: 16.0),
],
);
}
},
itemCount: isLoading ? images.length + 1 : images.length,
);
},
),
),
);
}
}
class RoundedImageWithShadow extends StatelessWidget {
final Uint8List imageData;
const RoundedImageWithShadow({Key? key, required this.imageData})
: super(key: key);
@override
Widget build(BuildContext context) {
return Container(
clipBehavior: Clip.antiAlias,
decoration: BoxDecoration(
borderRadius: BorderRadius.circular(20),
boxShadow: [
BoxShadow(
blurRadius: 2,
color: Colors.black.withAlpha(40),
spreadRadius: 2,
),
],
),
child: Image.memory(
imageData,
fit: BoxFit.cover,
),
);
}
}
void main() {
runApp(
MaterialApp(
home: ChangeNotifierProvider(
create: (_) => Images(),
child: const HomePage(),
),
debugShowCheckedModeBanner: false,
),
);
}
Refresh Indicator in Flutter
import 'package:flutter/foundation.dart';
import 'package:flutter/material.dart';
const allImages = [
'https://bit.ly/3x7J5Qt',
'https://bit.ly/3ywI8l6',
'https://bit.ly/36fNNj9',
'https://bit.ly/3jOueGG',
'https://bit.ly/3qYOtDm',
'https://bit.ly/3wt11Ec',
'https://bit.ly/3yvFg7X',
'https://bit.ly/3ywzOla',
'https://bit.ly/3wnASpW',
'https://bit.ly/3jXSDto',
];
class HomePage extends StatefulWidget {
const HomePage({Key? key}) : super(key: key);
@override
State<HomePage> createState() => _HomePageState();
}
class _HomePageState extends State<HomePage> {
final _images = [allImages.first];
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: const Text('Refresh Indicator in Flutter'),
),
body: RefreshIndicator(
onRefresh: () async {
final nextIndex = _images.length + 1;
if (nextIndex < allImages.length) {
setState(() {
_images.insert(0, allImages[nextIndex]);
});
}
},
child: ListView.builder(
physics: const AlwaysScrollableScrollPhysics(),
padding: const EdgeInsets.all(16),
itemCount: _images.length,
itemBuilder: (context, index) {
final imageUrl = _images[index];
return Column(
children: [
RoundedImageWithShadow(url: imageUrl),
const SizedBox(height: 16),
],
);
},
),
),
);
}
}
class RoundedImageWithShadow extends StatelessWidget {
final String url;
const RoundedImageWithShadow({Key? key, required this.url}) : super(key: key);
@override
Widget build(BuildContext context) {
return Container(
clipBehavior: Clip.antiAlias,
decoration: BoxDecoration(
borderRadius: BorderRadius.circular(20),
boxShadow: [
BoxShadow(
blurRadius: 2,
color: Colors.black.withAlpha(40),
spreadRadius: 2,
),
],
),
child: Image.network(url),
);
}
}
FlatMap in Dart
extension FlatMap<T> on T? {
E? flatMap<E>(E? Function(T) f) => this != null ? f(this!) : null;
}
AuthUser? get insteadOfThis {
final user = FirebaseAuth.instance.currentUser;
if (user != null) {
return AuthUser.fromFirebase(user);
} else {
return null;
}
}
AuthUser? get doThis =>
FirebaseAuth.instance.currentUser.flatMap((u) => AuthUser.fromFirebase(u));
OrientationBuilder in Flutter
import 'package:flutter/foundation.dart';
import 'package:flutter/material.dart';
class RoundedImageWithShadow extends StatelessWidget {
final String url;
const RoundedImageWithShadow({Key? key, required this.url}) : super(key: key);
@override
Widget build(BuildContext context) {
return Container(
clipBehavior: Clip.antiAlias,
decoration: BoxDecoration(
borderRadius: BorderRadius.circular(20),
boxShadow: [
BoxShadow(
blurRadius: 2,
color: Colors.black.withAlpha(40),
spreadRadius: 2,
),
],
),
child: Image.network(url),
);
}
}
class HomePage extends StatelessWidget {
const HomePage({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
return Scaffold(
body: SafeArea(
child: OrientationBuilder(
builder: (context, orientation) {
final int count;
switch (orientation) {
case Orientation.portrait:
count = 2;
break;
case Orientation.landscape:
count = 4;
break;
}
return GridView.count(
padding: const EdgeInsets.all(8.0),
crossAxisCount: count,
mainAxisSpacing: 8.0,
crossAxisSpacing: 8.0,
children: images
.map((url) => RoundedImageWithShadow(url: url))
.toList(),
);
},
),
),
);
}
}
final images = [
'https://bit.ly/3qJ2FCf',
'https://bit.ly/3Hs9JsV',
'https://bit.ly/3cfT6Cv',
'https://bit.ly/30wGnIE',
'https://bit.ly/3kJYsum',
'https://bit.ly/3oDoMaJ',
'https://bit.ly/3FndXQM',
'https://bit.ly/3ci4i1f',
];
Linear Gradient in Flutter
import 'package:flutter/foundation.dart';
import 'package:flutter/material.dart';
class HomePage extends StatelessWidget {
const HomePage({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: const Text('Linear Gradient in Flutter'),
),
body: const ImageWithShadow(url: 'https://bit.ly/3otHHog'),
);
}
}
class ImageWithShadow extends StatelessWidget {
final String url;
const ImageWithShadow({
Key? key,
required this.url,
}) : super(key: key);
@override
Widget build(BuildContext context) {
return Padding(
padding: const EdgeInsets.all(16.0),
child: Stack(
children: [
Positioned.fill(
child: Container(
decoration: BoxDecoration(
boxShadow: [
BoxShadow(
blurRadius: 10.0,
color: Colors.black.withOpacity(0.5),
offset: const Offset(0.0, 3.0),
)
],
borderRadius: const BorderRadius.all(Radius.circular(20)),
gradient: const LinearGradient(
begin: Alignment.topCenter,
end: Alignment.bottomCenter,
colors: [
Color.fromARGB(255, 176, 229, 251),
Color.fromARGB(255, 235, 202, 250)
],
),
),
),
),
Image.network(url),
],
),
);
}
}
Bloc Text Editing Controller in Flutter
import 'package:flutter/foundation.dart';
import 'package:flutter/material.dart';
import 'package:bloc/bloc.dart';
import 'package:flutter_bloc/flutter_bloc.dart';
abstract class Event {
const Event();
}
class SearchEvent extends Event {
final String searchString;
const SearchEvent(this.searchString);
}
class ClearSearch extends Event {}
class SearchBloc extends Bloc<Event, List<String>> {
static const names = ['foo', 'bar', 'baz'];
SearchBloc() : super(names) {
on<Event>((event, emit) {
if (event is SearchEvent) {
emit(names
.where((element) => element.contains(event.searchString))
.toList());
} else if (event is ClearSearch) {
emit(names);
}
});
}
}
class BlocTextEditingController extends TextEditingController {
SearchBloc? bloc;
BlocTextEditingController() {
addListener(() {
if (text.isEmpty) {
bloc?.add(ClearSearch());
} else {
bloc?.add(SearchEvent(text));
}
});
}
}
class HomePage extends StatefulWidget {
const HomePage({Key? key}) : super(key: key);
@override
State<HomePage> createState() => _HomePageState();
}
const largeStyle = TextStyle(fontSize: 30);
class _HomePageState extends State<HomePage> {
late final BlocTextEditingController _controller;
@override
void initState() {
_controller = BlocTextEditingController();
super.initState();
}
@override
void dispose() {
_controller.dispose();
super.dispose();
}
@override
Widget build(BuildContext context) {
_controller.bloc = BlocProvider.of<SearchBloc>(context);
return Scaffold(
appBar: AppBar(
title: Text('Bloc Search in Flutter'),
),
body: Padding(
padding: const EdgeInsets.all(8.0),
child: BlocBuilder<SearchBloc, List<String>>(
builder: (context, state) {
return ListView.builder(
itemBuilder: (context, index) {
if (index == 0) {
// search field
return TextField(
decoration: InputDecoration(
hintText: 'Enter search term here...',
hintStyle: largeStyle,
),
style: largeStyle,
controller: _controller,
);
} else {
final name = state[index - 1];
return ListTile(
title: Text(
name,
style: largeStyle,
),
);
}
},
itemCount: state.length + 1, // +1 for search
);
},
),
),
);
}
}
Blurred TabBar in Flutter
import 'package:flutter/foundation.dart';
import 'package:flutter/material.dart';
const images = [
'https://bit.ly/3x7J5Qt',
'https://bit.ly/3ywI8l6',
'https://bit.ly/36fNNj9',
'https://bit.ly/3jOueGG',
'https://bit.ly/3qYOtDm',
'https://bit.ly/3wt11Ec',
'https://bit.ly/3yvFg7X',
'https://bit.ly/3ywzOla',
'https://bit.ly/3wnASpW',
'https://bit.ly/3jXSDto',
];
class CustomTabBar extends StatelessWidget {
final List<IconButton> buttons;
const CustomTabBar({Key? key, required this.buttons}) : super(key: key);
@override
Widget build(BuildContext context) {
return Align(
alignment: Alignment.bottomCenter,
child: ClipRect(
child: Container(
height: 80,
color: Colors.white.withOpacity(0.4),
child: BackdropFilter(
filter: ImageFilter.blur(sigmaX: 4.0, sigmaY: 4.0),
child: Container(
width: double.infinity,
decoration: BoxDecoration(
color: Colors.white.withOpacity(0.5),
),
child: Padding(
padding: const EdgeInsets.only(bottom: 15),
child: Row(
crossAxisAlignment: CrossAxisAlignment.center,
mainAxisAlignment: MainAxisAlignment.spaceAround,
children: buttons,
),
),
),
),
),
),
);
}
}
const summerIcon = Icon(
Icons.surfing,
size: 40.0,
color: Colors.teal,
);
const autumnIcon = Icon(
Icons.nature_outlined,
size: 40.0,
color: Colors.black45,
);
const winterIcon = Icon(
Icons.snowboarding,
size: 40.0,
color: Colors.black45,
);
class HomePage extends StatelessWidget {
const HomePage({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('Blurred Tab Bar'),
),
body: Stack(
children: [
ListView.builder(
itemCount: images.length,
itemBuilder: (context, index) {
final url = images[index];
return Image.network(url);
},
),
CustomTabBar(
buttons: [
IconButton(
icon: summerIcon,
onPressed: () {
// implement me
},
),
IconButton(
icon: autumnIcon,
onPressed: () {
// implement me
},
),
IconButton(
icon: winterIcon,
onPressed: () {
// implement me
},
)
],
)
],
),
);
}
}
Play YouTube in Flutter
import 'package:flutter/foundation.dart';
import 'package:flutter/material.dart';
import 'package:webview_flutter/webview_flutter.dart';
const videoIds = [
'BHACKCNDMW8',
'26h9hBZFl7w',
'glENND73k4Q',
'd0tU18Ybcvk',
];
class VideoView extends StatelessWidget {
final String videoId;
final _key = UniqueKey();
VideoView({required this.videoId});
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('Watch a Video'),
),
body: Center(
child: Container(
height: 232.0,
child: WebView(
key: _key,
initialUrl: 'https://www.youtube.com/embed/$videoId',
javascriptMode: JavascriptMode.unrestricted,
),
),
),
);
}
}
class YouTubeVideoThumbnail extends StatelessWidget {
final String videoId;
final String thumbnailUrl;
const YouTubeVideoThumbnail({Key? key, required this.videoId})
: thumbnailUrl = 'https://img.youtube.com/vi/$videoId/maxresdefault.jpg',
super(key: key);
@override
Widget build(BuildContext context) {
return GestureDetector(
onTap: () {
Navigator.of(context).push(
MaterialPageRoute(
builder: (_) => VideoView(videoId: videoId),
),
);
},
child: Container(
height: 256.0,
clipBehavior: Clip.antiAlias,
decoration: BoxDecoration(
boxShadow: [
BoxShadow(
blurRadius: 10.0,
color: Colors.black.withAlpha(50),
spreadRadius: 10.0,
),
],
borderRadius: BorderRadius.circular(20),
image: DecorationImage(
fit: BoxFit.fitHeight,
image: NetworkImage(thumbnailUrl),
),
),
child: Center(
child: Icon(
Icons.play_arrow,
color: Colors.white,
size: 100.0,
),
),
),
);
}
}
class HomePage extends StatelessWidget {
const HomePage({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(title: Text('YouTube Videos in Flutter')),
body: ListView.builder(
itemCount: videoIds.length,
itemBuilder: (context, index) {
final videoId = videoIds[index];
return Padding(
padding: const EdgeInsets.all(8.0),
child: YouTubeVideoThumbnail(videoId: videoId),
);
},
),
);
}
}
ListView Background in Flutter
import 'package:flutter/foundation.dart';
import 'package:flutter/material.dart';
class ListItem {
const ListItem();
factory ListItem.emptyTile() => EmptyTile();
factory ListItem.tile(
String title,
String subTitle,
) =>
Tile(
title,
subTitle,
);
}
class Tile extends ListItem {
final String title;
final String subTitle;
const Tile(this.title, this.subTitle) : super();
}
class EmptyTile extends ListItem {}
final items = [
for (var i = 1; i <= 6; i++) ListItem.tile('Title $i', 'Sub title $i'),
ListItem.emptyTile(),
for (var i = 7; i <= 12; i++) ListItem.tile('Title $i', 'Sub title $i'),
];
class Background extends StatelessWidget {
final Widget child;
const Background({Key? key, required this.child}) : super(key: key);
@override
Widget build(BuildContext context) {
return Container(
clipBehavior: Clip.antiAlias,
decoration: BoxDecoration(
borderRadius: BorderRadius.circular(20),
image: DecorationImage(
fit: BoxFit.fitHeight,
image: NetworkImage('https://bit.ly/3jXSDto'),
),
),
child: child,
);
}
}
class HomePage extends StatelessWidget {
const HomePage({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
return Scaffold(
body: Background(
child: ListView.builder(
padding: EdgeInsets.zero,
itemCount: items.length,
itemBuilder: (context, index) {
final item = items[index];
if (item is Tile) {
return Container(
color: Colors.grey[200],
child: ListTile(
title: Text(item.title),
subtitle: Text(item.subTitle),
),
);
} else if (item is EmptyTile) {
return SizedBox(
height: 450,
);
} else {
throw 'unexpcted item';
}
},
),
),
);
}
}
Integer to Binary in Dart
extension ToBinary on int {
String toBinary(
int len, {
int separateAtLength = 4,
String separator = ',',
}) =>
toRadixString(2)
.padLeft(len, '0')
.splitByLength(separateAtLength)
.join(separator);
}
void testIt() {
assert(1.toBinary(8) == '0000,0001');
assert(2.toBinary(4) == '0010');
assert(3.toBinary(16) == '0000,0000,0000,0011');
assert(255.toBinary(8, separateAtLength: 8) == '11111111');
assert(255.toBinary(8, separateAtLength: 4) == '1111,1111');
}
extension SplitByLength on String {
Iterable<String> splitByLength(int len, {String filler = '0'}) sync* {
final missingFromLength =
length % len == 0 ? 0 : len - (characters.length % len);
final expectedLength = length + missingFromLength;
final src = padLeft(expectedLength, filler);
final chars = src.characters;
for (var i = 0; i < chars.length; i += len) {
yield chars.getRange(i, i + len).toString();
}
}
}
Split String by Length in Dart
void testIt() {
assert('dartlang'
.splitByLength(5, filler: '💙')
.isEqualTo(['💙💙dar', 'tlang']));
assert('0100010'.splitByLength(4).isEqualTo(['0010', '0010']));
assert('foobar'.splitByLength(3).isEqualTo(['foo', 'bar']));
assert('flutter'.splitByLength(4, filler: 'X').isEqualTo(['Xflu', 'tter']));
assert('dart'.splitByLength(5, filler: '').isEqualTo(['dart']));
}
extension SplitByLength on String {
Iterable<String> splitByLength(int len, {String filler = '0'}) sync* {
final missingFromLength =
length % len == 0 ? 0 : len - (characters.length % len);
final expectedLength = length + missingFromLength;
final src = padLeft(expectedLength, filler);
final chars = src.characters;
for (var i = 0; i < chars.length; i += len) {
yield chars.getRange(i, i + len).toString();
}
}
}
Image Tint in Flutter
import 'package:flutter/foundation.dart';
import 'package:flutter/material.dart';
enum OverlayColor { brown, orange, yellow, green, blue }
extension Color on OverlayColor {
MaterialColor get color {
switch (this) {
case OverlayColor.blue:
return Colors.blue;
case OverlayColor.brown:
return Colors.brown;
case OverlayColor.green:
return Colors.green;
case OverlayColor.orange:
return Colors.orange;
case OverlayColor.yellow:
return Colors.yellow;
}
}
}
extension Title on OverlayColor {
String get title => toString().split('.').last;
}
extension ToTextButtonWithValue on OverlayColor {
TextButtonWithValue<OverlayColor> toTextButtonWithValue(
OnTextButtonWithValuePressed onPressed) {
return TextButtonWithValue(
value: this,
onPressed: onPressed,
child: Text(title),
);
}
}
typedef OnTextButtonWithValuePressed<T> = void Function(T value);
class TextButtonWithValue<T> extends StatelessWidget {
final T value;
final OnTextButtonWithValuePressed onPressed;
final Widget child;
const TextButtonWithValue({
Key? key,
required this.value,
required this.onPressed,
required this.child,
}) : super(key: key);
@override
Widget build(BuildContext context) {
return TextButton(
onPressed: () {
onPressed(value);
},
child: child,
);
}
}
class HomePage extends StatefulWidget {
const HomePage({Key? key}) : super(key: key);
@override
State<HomePage> createState() => _HomePageState();
}
class _HomePageState extends State<HomePage> {
OverlayColor? _overlayColor;
ColorFilter? getcolorFilter() {
final overlayColor = _overlayColor;
if (overlayColor == null) {
return null;
}
return ColorFilter.mode(
overlayColor.color,
BlendMode.colorBurn,
);
}
Iterable<Widget> overlayColorButtons() {
return OverlayColor.values.map((overlayColor) {
return Expanded(
flex: 1,
child: Container(
child: overlayColor.toTextButtonWithValue(
(value) {
setState(() {
_overlayColor = value;
});
},
),
),
);
});
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('Tinting Images in Flutter'),
),
body: Padding(
padding: const EdgeInsets.all(16.0),
child: Column(
children: [
Container(
height: 250.0,
clipBehavior: Clip.antiAlias,
decoration: BoxDecoration(
borderRadius: BorderRadius.circular(20),
image: DecorationImage(
colorFilter: getcolorFilter(),
fit: BoxFit.fitHeight,
image: NetworkImage('https://bit.ly/3jOueGG'),
),
),
),
SizedBox(height: 16.0),
Row(
children: overlayColorButtons().toList(),
)
],
),
),
);
}
}
SlideTransition in Flutter
import 'package:flutter/foundation.dart';
import 'package:flutter/material.dart';
import 'package:flutter/gestures.dart';
class _HomePageState extends State<HomePage>
with SingleTickerProviderStateMixin {
late final _controller = AnimationController(
duration: Duration(milliseconds: 500),
vsync: this,
);
late final _animation = Tween<Offset>(
begin: Offset(0.0, 0.0),
end: Offset(-0.83, 0.0),
).animate(
CurvedAnimation(
parent: _controller,
curve: Curves.easeInQuint,
),
);
var _isExpanded = false;
@override
void dispose() {
super.dispose();
_controller.dispose();
}
@override
Widget build(BuildContext context) {
_controller.forward();
return Scaffold(
body: SizedBox.expand(
child: Stack(
fit: StackFit.passthrough,
children: [
Image.network(
'https://bit.ly/3BWYDbz',
fit: BoxFit.fitHeight,
),
Positioned(
top: 200.0,
child: SlideTransition(
position: _animation,
child: GestureDetector(
onTap: () {
_isExpanded = !_isExpanded;
if (_isExpanded) {
_controller.reverse();
} else {
_controller.forward();
}
},
child: Box(),
),
),
),
],
),
),
);
}
}
class HomePage extends StatefulWidget {
const HomePage({Key? key}) : super(key: key);
@override
State<HomePage> createState() => _HomePageState();
}
class Box extends StatelessWidget {
const Box({
Key? key,
}) : super(key: key);
@override
Widget build(BuildContext context) {
return Container(
decoration: BoxDecoration(
color: Colors.blue[200]?.withAlpha(200),
border: Border.all(
color: Colors.blue,
style: BorderStyle.solid,
width: 1.0,
),
borderRadius: BorderRadius.only(
topRight: Radius.circular(10),
bottomRight: Radius.circular(10),
),
),
child: Padding(
padding: const EdgeInsets.all(8.0),
child: Row(
children: [
Text(
'By: Jesper Anhede',
style: TextStyle(
fontSize: 18.0,
),
),
SizedBox(width: 10.0),
Icon(
Icons.info,
color: Colors.pink[400],
),
],
),
),
);
}
}
Expansion Panels and Lists in Flutter
import 'package:flutter/foundation.dart';
import 'package:flutter/material.dart';
class Event {
final String title;
final String details;
final String imageUrl;
bool isExpanded = false;
Event({
required this.title,
required this.details,
required this.imageUrl,
});
@override
bool operator ==(covariant Event other) => title == other.title;
}
const diwaliDetails =
'''Diwali, or Dipawali, is India's biggest and most important holiday of the year. The festival gets its name from the row (avali) of clay lamps (deepa) that Indians light outside their homes to symbolize the inner light that protects from spiritual darkness. This festival is as important to Hindus as the Christmas holiday is to Christians.''';
const halloweenDetails =
'''Halloween or Hallowe'en, less commonly known as Allhalloween, All Hallows' Eve, or All Saints' Eve, is a celebration observed in many countries on 31 October, the eve of the Western Christian feast of All Hallows' Day.''';
final events = [
Event(
title: 'Diwali',
details: diwaliDetails,
imageUrl: 'https://bit.ly/3mGg8YW',
),
Event(
title: 'Halloween',
details: halloweenDetails,
imageUrl: 'https://bit.ly/3wb1w7j',
),
];
extension ToPanel on Event {
ExpansionPanel toPanel() {
return ExpansionPanel(
headerBuilder: (context, isExpanded) {
return Padding(
padding: const EdgeInsets.all(8.0),
child: Text(
title,
style: TextStyle(fontSize: 30.0),
),
);
},
isExpanded: isExpanded,
body: Container(
height: 250,
width: double.infinity,
decoration: BoxDecoration(
image: DecorationImage(
fit: BoxFit.fitWidth,
colorFilter: ColorFilter.mode(
Colors.black.withOpacity(0.5),
BlendMode.luminosity,
),
image: NetworkImage(imageUrl),
),
),
child: SingleChildScrollView(
child: Padding(
padding: const EdgeInsets.all(8.0),
child: Text(
details,
textAlign: TextAlign.center,
style: TextStyle(fontSize: 20, color: Colors.white, shadows: [
Shadow(
blurRadius: 1.0,
offset: Offset.zero,
color: Colors.black,
)
]),
),
),
),
),
);
}
}
class HomePage extends StatefulWidget {
HomePage({Key? key}) : super(key: key);
@override
State<HomePage> createState() => _HomePageState();
}
class _HomePageState extends State<HomePage> {
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('Expansion Panels in Flutter'),
),
body: SingleChildScrollView(
child: ExpansionPanelList(
children: events.map((e) => e.toPanel()).toList(),
expansionCallback: (panelIndex, isExpanded) {
setState(() {
events[panelIndex].isExpanded = !isExpanded;
});
},
),
),
);
}
}
Complete CRUD App in Flutter
//Want to support my work 🤝? https://buymeacoffee.com/vandad
import 'package:flutter/foundation.dart';
import 'package:flutter/material.dart';
import 'package:path_provider/path_provider.dart';
import 'package:sqflite/sqflite.dart';
import 'package:path_provider/path_provider.dart'
show getApplicationDocumentsDirectory;
class Person implements Comparable {
final int id;
final String firstName;
final String lastName;
const Person(this.id, this.firstName, this.lastName);
String get fullName => '$firstName $lastName';
Person.fromData(Map<String, Object?> data)
: id = data['ID'] as int,
firstName = data['FIRST_NAME'] as String,
lastName = data['LAST_NAME'] as String;
@override
int compareTo(covariant Person other) => other.id.compareTo(id);
@override
bool operator ==(covariant Person other) => id == other.id;
@override
String toString() =>
'Person, ID = $id, firstName = $firstName, lastName = $lastName';
}
class PersonDB {
final _controller = StreamController<List<Person>>.broadcast();
List<Person> _persons = [];
Database? _db;
final String dbName;
PersonDB({required this.dbName});
Future<bool> close() async {
final db = _db;
if (db == null) {
return false;
}
await db.close();
return true;
}
Future<bool> open() async {
if (_db != null) {
return true;
}
final directory = await getApplicationDocumentsDirectory();
final path = '${directory.path}/$dbName';
try {
final db = await openDatabase(path);
_db = db;
// create the table if it doesn't exist
final create = '''CREATE TABLE IF NOT EXISTS PEOPLE (
ID INTEGER PRIMARY KEY AUTOINCREMENT,
FIRST_NAME STRING NOT NULL,
LAST_NAME STRING NOT NULL
)''';
await db.execute(create);
// if everything went fine, we then read all the objects
// and populate the stream
_persons = await _fetchPeople();
_controller.add(_persons);
return true;
} catch (e) {
print('error = $e');
return false;
}
}
Future<List<Person>> _fetchPeople() async {
final db = _db;
if (db == null) {
return [];
}
try {
// read the existing data if any
final readResult = await db.query(
'PEOPLE',
distinct: true,
columns: ['ID', 'FIRST_NAME', 'LAST_NAME'],
orderBy: 'ID',
);
final people = readResult.map((row) => Person.fromData(row)).toList();
return people;
} catch (e) {
print('error = $e');
return [];
}
}
Future<bool> delete(Person person) async {
final db = _db;
if (db == null) {
return false;
}
try {
final deletedCount = await db.delete(
'PEOPLE',
where: 'ID = ?',
whereArgs: [person.id],
);
// delete it locally as well
if (deletedCount == 1) {
_persons.remove(person);
_controller.add(_persons);
return true;
} else {
return false;
}
} catch (e) {
print('Error inserting $e');
return false;
}
}
Future<bool> create(String firstName, String lastName) async {
final db = _db;
if (db == null) {
return false;
}
try {
final id = await db.insert(
'PEOPLE',
{
'FIRST_NAME': firstName,
'LAST_NAME': lastName,
},
);
final person = Person(id, firstName, lastName);
_persons.add(person);
_controller.add(_persons);
return true;
} catch (e) {
print('Error inserting $e');
return false;
}
}
// uses the person's id to update its first name and last name
Future<bool> update(Person person) async {
final db = _db;
if (db == null) {
return false;
}
try {
final updatedCount = await db.update(
'PEOPLE',
{
'FIRST_NAME': person.firstName,
'LAST_NAME': person.lastName,
},
where: 'ID = ?',
whereArgs: [person.id],
);
if (updatedCount == 1) {
_persons.removeWhere((p) => p.id == person.id);
_persons.add(person);
_controller.add(_persons);
return true;
} else {
return false;
}
} catch (e) {
print('Error inserting $e');
return false;
}
}
Stream<List<Person>> all() =>
_controller.stream.map((event) => event..sort());
}
typedef OnCompose = void Function(String firstName, String lastName);
class ComposeWidget extends StatefulWidget {
final OnCompose onCompose;
const ComposeWidget({Key? key, required this.onCompose}) : super(key: key);
@override
State<ComposeWidget> createState() => _ComposeWidgetState();
}
class _ComposeWidgetState extends State<ComposeWidget> {
final firstNameController = TextEditingController();
final lastNameController = TextEditingController();
@override
void dispose() {
firstNameController.dispose();
lastNameController.dispose();
super.dispose();
}
@override
Widget build(BuildContext context) {
return Padding(
padding: const EdgeInsets.all(8.0),
child: Column(children: [
TextField(
style: TextStyle(fontSize: 24),
decoration: InputDecoration(
hintText: 'Enter first name',
),
controller: firstNameController,
),
TextField(
style: TextStyle(fontSize: 24),
decoration: InputDecoration(
hintText: 'Enter last name',
),
controller: lastNameController,
),
TextButton(
onPressed: () {
final firstName = firstNameController.text;
final lastName = lastNameController.text;
widget.onCompose(firstName, lastName);
},
child: Text(
'Add to list',
style: TextStyle(fontSize: 24),
),
),
]),
);
}
}
class HomePage extends StatefulWidget {
HomePage({Key? key}) : super(key: key);
@override
State<HomePage> createState() => _HomePageState();
}
class _HomePageState extends State<HomePage> {
late final PersonDB _crudStorage;
@override
void initState() {
_crudStorage = PersonDB(dbName: 'db.sqlite');
_crudStorage.open();
super.initState();
}
@override
void dispose() {
_crudStorage.close();
super.dispose();
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('SQLite in Flutter'),
),
body: StreamBuilder(
stream: _crudStorage.all(),
builder: (context, snapshot) {
switch (snapshot.connectionState) {
case ConnectionState.active:
case ConnectionState.waiting:
if (snapshot.data == null) {
return Center(child: CircularProgressIndicator());
}
final people = snapshot.data as List<Person>;
return Column(
children: [
ComposeWidget(
onCompose: (firstName, lastName) async {
await _crudStorage.create(firstName, lastName);
},
),
Expanded(
child: ListView.builder(
itemCount: people.length,
itemBuilder: (context, index) {
final person = people[index];
return ListTile(
onTap: () async {
final update =
await showUpdateDialog(context, person);
if (update == null) {
return;
}
await _crudStorage.update(update);
},
title: Text(
person.fullName,
style: TextStyle(fontSize: 24),
),
subtitle: Text(
'ID: ${person.id}',
style: TextStyle(fontSize: 18),
),
trailing: TextButton(
onPressed: () async {
final shouldDelete =
await showDeleteDialog(context);
if (shouldDelete) {
await _crudStorage.delete(person);
}
},
child: Icon(
Icons.disabled_by_default_rounded,
color: Colors.red,
),
),
);
},
),
),
],
);
default:
return Center(child: CircularProgressIndicator());
}
},
),
);
}
}
final firstNameController = TextEditingController();
final lastNameController = TextEditingController();
Future<Person?> showUpdateDialog(BuildContext context, Person person) {
firstNameController.text = person.firstName;
lastNameController.text = person.lastName;
return showDialog(
context: context,
builder: (context) {
return AlertDialog(
content: Column(
mainAxisSize: MainAxisSize.min,
children: [
Text('Enter your udpated values here:'),
TextField(controller: firstNameController),
TextField(controller: lastNameController),
],
),
actions: [
TextButton(
onPressed: () {
Navigator.of(context).pop(null);
},
child: Text('Cancel'),
),
TextButton(
onPressed: () {
final newPerson = Person(
person.id,
firstNameController.text,
lastNameController.text,
);
Navigator.of(context).pop(newPerson);
},
child: Text('Save'),
),
],
);
},
).then((value) {
if (value is Person) {
return value;
} else {
return null;
}
});
}
Future<bool> showDeleteDialog(BuildContext context) {
return showDialog(
context: context,
builder: (context) {
return AlertDialog(
content: Text('Are you sure you want to delete this item?'),
actions: [
TextButton(
onPressed: () {
Navigator.of(context).pop(false);
},
child: Text('No'),
),
TextButton(
onPressed: () {
Navigator.of(context).pop(true);
},
child: Text('Delete'),
)
],
);
},
).then(
(value) {
if (value is bool) {
return value;
} else {
return false;
}
},
);
}
SQLite Storage in Flutter
import 'package:flutter/foundation.dart';
import 'package:flutter/material.dart';
import 'package:path_provider/path_provider.dart';
import 'package:sqflite/sqflite.dart';
import 'package:path_provider/path_provider.dart'
show getApplicationDocumentsDirectory;
class HomePage extends StatefulWidget {
const HomePage({Key? key}) : super(key: key);
@override
State<HomePage> createState() => _HomePageState();
}
class Person implements Comparable {
final int id;
final String firstName;
final String lastName;
const Person(this.id, this.firstName, this.lastName);
String get fullName => '$firstName $lastName';
Person.fromData(Map<String, Object?> data)
: id = data['ID'] as int,
firstName = data['FIRST_NAME'] as String,
lastName = data['LAST_NAME'] as String;
@override
int compareTo(covariant Person other) => other.id.compareTo(id);
}
typedef OnCompose = void Function(String firstName, String lastName);
class ComposeWidget extends StatefulWidget {
final OnCompose onCompose;
const ComposeWidget({Key? key, required this.onCompose}) : super(key: key);
@override
State<ComposeWidget> createState() => _ComposeWidgetState();
}
class _ComposeWidgetState extends State<ComposeWidget> {
final firstNameController = TextEditingController();
final lastNameController = TextEditingController();
@override
void dispose() {
firstNameController.dispose();
lastNameController.dispose();
super.dispose();
}
@override
Widget build(BuildContext context) {
return Padding(
padding: const EdgeInsets.all(8.0),
child: Column(children: [
TextField(
style: TextStyle(fontSize: 24),
decoration: InputDecoration(
hintText: 'Enter first name',
),
controller: firstNameController,
),
TextField(
style: TextStyle(fontSize: 24),
decoration: InputDecoration(
hintText: 'Enter last name',
),
controller: lastNameController,
),
TextButton(
onPressed: () {
final firstName = firstNameController.text;
final lastName = lastNameController.text;
widget.onCompose(firstName, lastName);
},
child: Text(
'Add to list',
style: TextStyle(fontSize: 24),
),
),
]),
);
}
}
class _HomePageState extends State<HomePage> {
late final Database db;
bool hasSetUpAlready = false;
Future<bool> setupDatabase() async {
if (hasSetUpAlready == false) {
final directory = await getApplicationDocumentsDirectory();
final path = '${directory.path}/db.sqlite';
try {
db = await openDatabase(path);
// create the table if it doesn't exist
final create = '''CREATE TABLE IF NOT EXISTS PEOPLE (
ID INTEGER PRIMARY KEY AUTOINCREMENT,
FIRST_NAME STRING NOT NULL,
LAST_NAME STRING NOT NULL
)''';
await db.execute(create);
hasSetUpAlready = true;
return true;
} catch (e) {
print('error = $e');
hasSetUpAlready = false;
return false;
}
} else {
return true;
}
}
Future<List<Person>> fetchPersons() async {
if (!await setupDatabase()) {
return [];
}
try {
// read the existing data if any
final readResult = await db.query(
'PEOPLE',
distinct: true,
columns: ['ID', 'FIRST_NAME', 'LAST_NAME'],
orderBy: 'ID',
);
final people = readResult.map((row) => Person.fromData(row)).toList()
..sort();
return people;
} catch (e) {
print('error = $e');
return [];
}
}
Future<bool> addPerson(String firstName, String lastName) async {
try {
await db.insert(
'PEOPLE',
{
'FIRST_NAME': firstName,
'LAST_NAME': lastName,
},
);
return true;
} catch (e) {
print('Error inserting $e');
return false;
}
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('SQLite in Flutter'),
),
body: FutureBuilder(
future: fetchPersons(),
builder: (context, snapshot) {
switch (snapshot.connectionState) {
case ConnectionState.done:
final people = snapshot.data as List<Person>;
return Column(
children: [
ComposeWidget(
onCompose: (firstName, lastName) async {
await addPerson(firstName, lastName);
setState(() {});
},
),
Expanded(
child: ListView.builder(
itemCount: people.length,
itemBuilder: (context, index) {
final person = people[index];
return ListTile(
title: Text(
person.fullName,
style: TextStyle(fontSize: 24),
),
subtitle: Text(
'ID: ${person.id}',
style: TextStyle(fontSize: 18),
),
);
},
),
),
],
);
default:
return CircularProgressIndicator();
}
},
),
);
}
}
Circular Progress with Percentage in Flutter
import 'package:flutter/foundation.dart';
import 'package:flutter/material.dart';
class SizedCircularProgressIndicator extends StatelessWidget {
final double progress;
final double width;
final double height;
final TextStyle? textStyle;
const SizedCircularProgressIndicator({
Key? key,
this.textStyle,
required this.progress,
required this.width,
required this.height,
}) : super(key: key);
TextStyle get style => textStyle ?? TextStyle(fontSize: 30.0);
int get _progress => (progress * 100.0).toInt();
@override
Widget build(BuildContext context) {
return Stack(
alignment: Alignment.center,
children: [
Text('$_progress%', style: style),
SizedBox(
width: width,
height: height,
child: CircularProgressIndicator(
backgroundColor: Colors.white70,
value: progress,
color: Colors.blueAccent,
strokeWidth: 3.0,
),
),
],
);
}
}
const images = [
'https://bit.ly/3x7J5Qt',
'https://bit.ly/3ywI8l6',
'https://bit.ly/36fNNj9',
'https://bit.ly/3jOueGG',
'https://bit.ly/3qYOtDm',
'https://bit.ly/3wt11Ec',
'https://bit.ly/3yvFg7X',
'https://bit.ly/3ywzOla',
'https://bit.ly/3wnASpW',
'https://bit.ly/3jXSDto',
];
class HomePage extends StatelessWidget {
const HomePage({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
return Scaffold(
body: PageView.builder(
scrollDirection: Axis.horizontal,
itemCount: images.length,
itemBuilder: (context, index) {
return WithBlurredBackground(imageUrl: images[index]);
},
),
);
}
}
class WithBlurredBackground extends StatelessWidget {
final String imageUrl;
const WithBlurredBackground({Key? key, required this.imageUrl})
: super(key: key);
@override
Widget build(BuildContext context) {
return SizedBox.expand(
child: Stack(
alignment: Alignment.center,
fit: StackFit.passthrough,
children: [
SizedBox.expand(
child: ClipRect(
child: ImageFiltered(
imageFilter: ImageFilter.blur(
sigmaX: 10.0,
sigmaY: 10.0,
),
child: Image.network(
imageUrl,
fit: BoxFit.fitHeight,
),
),
),
),
NetworkImageWithProgress(url: imageUrl),
],
),
);
}
}
class NetworkImageWithProgress extends StatelessWidget {
final String url;
const NetworkImageWithProgress({Key? key, required this.url})
: super(key: key);
@override
Widget build(BuildContext context) {
return Image.network(
url,
loadingBuilder: (context, child, loadingProgress) {
final totalBytes = loadingProgress?.expectedTotalBytes;
final bytesLoaded = loadingProgress?.cumulativeBytesLoaded;
if (totalBytes != null && bytesLoaded != null) {
return SizedCircularProgressIndicator(
height: 100,
width: 100,
progress: bytesLoaded / totalBytes,
);
} else {
return child;
}
},
errorBuilder: (context, error, stackTrace) {
return Text('Error!');
},
);
}
}
Opening URLs in Flutter
import 'package:flutter/foundation.dart';
import 'package:flutter/material.dart';
import 'package:url_launcher/url_launcher.dart';
class Person {
final String profileUrl;
final String name;
final String email;
final String phoneNumber;
final String websiteUrl;
const Person({
Key? key,
required this.profileUrl,
required this.name,
required this.email,
required this.phoneNumber,
required this.websiteUrl,
});
Person.vandad()
: profileUrl = 'https://bit.ly/3jwusS0',
name = 'Vandad Nahavandipoor',
email = 'vandad.np@gmail.com',
phoneNumber = '071234567',
websiteUrl = 'https://pixolity.se';
}
void open(String url) async {
if (await canLaunch(url)) {
await launch(url);
}
}
class PersonNameView extends StatelessWidget {
final Person person;
const PersonNameView(this.person, {Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
return Text(
person.name,
style: TextStyle(
fontSize: 20,
fontWeight: FontWeight.bold,
color: Colors.black,
),
);
}
}
class PersonEmailView extends StatelessWidget {
final Person person;
const PersonEmailView(this.person, {Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
return TextButton(
onPressed: () {
open('mailto:${person.email}');
},
child: Text(
'💌 Email me',
style: TextStyle(fontSize: 20.0),
),
);
}
}
class PersonPhoneView extends StatelessWidget {
final Person person;
const PersonPhoneView(this.person, {Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
return TextButton(
onPressed: () {
open('tel://${person.phoneNumber}');
},
child: Text(
'🤙🏻 Call me',
style: TextStyle(fontSize: 20.0),
),
);
}
}
class PersonWebsiteView extends StatelessWidget {
final Person person;
const PersonWebsiteView(this.person, {Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
return TextButton(
onPressed: () {
open(person.websiteUrl);
},
child: Text(
'🌍 Visit my website',
style: TextStyle(fontSize: 20.0),
),
);
}
}
const bigText = TextStyle(fontSize: 20.0);
class PersonView extends StatelessWidget {
final Person person;
const PersonView({Key? key, required this.person}) : super(key: key);
@override
Widget build(BuildContext context) {
return Container(
decoration: BoxDecoration(
color: Colors.blue[50],
borderRadius: BorderRadius.circular(16.0),
border: Border.all(color: Colors.white, width: 3.0),
boxShadow: [
BoxShadow(
blurRadius: 30.0,
color: Colors.black.withAlpha(50),
spreadRadius: 20.0,
),
]),
child: Padding(
padding: const EdgeInsets.all(16.0),
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: [
CircleAvatar(
radius: 100.0,
backgroundImage: NetworkImage(person.profileUrl),
),
SizedBox(height: 10),
PersonNameView(person),
PersonEmailView(person),
PersonPhoneView(person),
PersonWebsiteView(person)
],
),
),
);
}
}
class HomePage extends StatelessWidget {
const HomePage({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
return Scaffold(
body: Center(
child: SingleChildScrollView(
child: PersonView(
person: Person.vandad(),
),
),
),
);
}
}
Commodore 64 Screen in Flutter
import 'package:flutter/foundation.dart';
import 'package:flutter/material.dart';
const textColor = Color.fromRGBO(156, 156, 247, 1);
class BoxPainter extends CustomPainter {
final bool isBlinking;
BoxPainter({required this.isBlinking});
@override
void paint(Canvas canvas, Size size) {
if (isBlinking) {
final rect = Rect.fromLTWH(
size.width / 20.0,
size.height / 2.8,
size.width / 24.0,
size.height / 13.0,
);
final paint = Paint()..color = textColor;
canvas.drawRect(rect, paint);
}
}
@override
bool shouldRepaint(covariant CustomPainter oldDelegate) => true;
}
class ReadyPainter extends CustomPainter {
@override
void paint(Canvas canvas, Size size) {
final textStyle = TextStyle(
color: textColor,
fontSize: size.width / 45.0,
fontFamily: 'C64',
);
final span = TextSpan(
text: 'READY',
style: textStyle,
);
final painter = TextPainter(
text: span,
textDirection: TextDirection.ltr,
);
painter.layout(
minWidth: 0,
maxWidth: size.width,
);
final offset = Offset(
painter.width / 2.0,
painter.height * 8.0,
);
painter.paint(canvas, offset);
}
@override
bool shouldRepaint(covariant CustomPainter oldDelegate) => false;
}
class SubTitlePainter extends CustomPainter {
@override
void paint(Canvas canvas, Size size) {
final textStyle = TextStyle(
color: textColor,
fontSize: size.width / 45.0,
fontFamily: 'C64',
);
final span = TextSpan(
text: '64K RAM SYSTEM 38911 BASIC BYTES FREE',
style: textStyle,
);
final painter = TextPainter(
text: span,
textDirection: TextDirection.ltr,
);
painter.layout(
minWidth: 0,
maxWidth: size.width,
);
final offset = Offset(
size.width - painter.width - (size.width / 11),
painter.height * 6.0,
);
painter.paint(canvas, offset);
}
@override
bool shouldRepaint(covariant CustomPainter oldDelegate) => false;
}
class TitlePainter extends CustomPainter {
@override
void paint(Canvas canvas, Size size) {
final textStyle = TextStyle(
color: textColor,
fontSize: size.width / 40.0,
fontFamily: 'C64',
);
final span = TextSpan(
text: '**** COMMODORE 64 BASIC V2 ****',
style: textStyle,
);
final painter = TextPainter(
text: span,
textDirection: TextDirection.ltr,
);
painter.layout(
minWidth: 0,
maxWidth: size.width,
);
final offset = Offset(
size.width - painter.width - (size.width / 9),
size.height / 6,
);
painter.paint(canvas, offset);
}
@override
bool shouldRepaint(covariant CustomPainter oldDelegate) => false;
}
class BackgroundPainter extends CustomPainter {
@override
void paint(Canvas canvas, Size size) {
final border = size.width / 20.0;
final color = Color.fromRGBO(
58,
57,
213,
1,
);
final paint = Paint()..color = color;
final rect = Rect.fromLTWH(
border,
border,
size.width - (border * 2.0),
size.height - (border * 2.0),
);
canvas.drawRect(rect, paint);
}
@override
bool shouldRepaint(covariant CustomPainter oldDelegate) => false;
}
class BorderPainter extends CustomPainter {
@override
void paint(Canvas canvas, Size size) {
final paint = Paint()..color = textColor;
final rect = Rect.fromLTWH(
0.0,
0.0,
size.width,
size.height,
);
canvas.drawRect(rect, paint);
}
@override
bool shouldRepaint(covariant CustomPainter oldDelegate) => false;
}
class Commodore64Painter extends CustomPainter {
final bool isBlinking;
late final List<CustomPainter> painters;
Commodore64Painter({required this.isBlinking}) {
painters = [
BorderPainter(),
BackgroundPainter(),
TitlePainter(),
SubTitlePainter(),
ReadyPainter(),
BoxPainter(isBlinking: isBlinking)
];
}
@override
void paint(Canvas canvas, Size size) {
painters.forEach(
(p) => p.paint(
canvas,
size,
),
);
}
@override
bool shouldRepaint(covariant CustomPainter oldDelegate) => painters
.map((p) => p.shouldRepaint(oldDelegate))
.reduce((p1, p2) => p1 || p2);
}
class Commodore64 extends StatefulWidget {
const Commodore64({Key? key}) : super(key: key);
@override
State<Commodore64> createState() => _Commodore64State();
}
class _Commodore64State extends State<Commodore64> {
bool _isBlinking = false;
final timer = Stream.periodic(Duration(seconds: 1), (value) => value);
void _triggerRedraw() async {
await for (final _ in timer) {
setState(() {
_isBlinking = !_isBlinking;
});
}
}
@override
void initState() {
super.initState();
_triggerRedraw();
}
@override
Widget build(BuildContext context) {
return LayoutBuilder(builder: (context, constraints) {
return Container(
width: constraints.maxWidth,
height: constraints.maxWidth / (16.0 / 9.0),
child: CustomPaint(
painter: Commodore64Painter(isBlinking: _isBlinking),
),
);
});
}
}
class HomePage extends StatelessWidget {
const HomePage({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
return Scaffold(
body: Center(
child: Commodore64(),
),
);
}
}
Animated Lists in Flutter
import 'package:flutter/foundation.dart';
import 'package:flutter/material.dart';
class NetworkImage extends StatelessWidget {
final String url;
const NetworkImage({
Key? key,
required this.url,
}) : super(key: key);
@override
Widget build(BuildContext context) {
return Image.network(
url,
loadingBuilder: (context, child, loadingProgress) {
final totalBytes = loadingProgress?.expectedTotalBytes;
final bytesLoaded = loadingProgress?.cumulativeBytesLoaded;
if (totalBytes != null && bytesLoaded != null) {
return LinearProgressIndicator(
value: bytesLoaded / totalBytes,
);
} else {
return child;
}
},
errorBuilder: (context, error, stackTrace) {
return Text('Error!');
},
);
}
}
class NetworkImageCard extends StatelessWidget {
final String url;
const NetworkImageCard({
Key? key,
required this.url,
}) : super(key: key);
@override
Widget build(BuildContext context) {
return Center(
child: Container(
clipBehavior: Clip.antiAlias,
decoration: BoxDecoration(
borderRadius: BorderRadius.circular(20.0),
),
child: NetworkImage(
url: url,
),
),
);
}
}
const imageUrls = [
'https://bit.ly/3x7J5Qt',
'https://bit.ly/3ywI8l6',
'https://bit.ly/36fNNj9',
'https://bit.ly/3jOueGG',
'https://bit.ly/3qYOtDm',
'https://bit.ly/3wt11Ec',
'https://bit.ly/3yvFg7X',
'https://bit.ly/3ywzOla',
'https://bit.ly/3wnASpW',
'https://bit.ly/3jXSDto',
];
Stream<String> images() => Stream.periodic(
Duration(seconds: 3),
(index) => index % imageUrls.length,
).map((index) => imageUrls[index]);
class HomePage extends StatefulWidget {
const HomePage({Key? key}) : super(key: key);
@override
State<HomePage> createState() => _HomePageState();
}
class _HomePageState extends State<HomePage> {
final GlobalKey<AnimatedListState> _key = GlobalKey();
List<String> imageUrls = [];
void populateList() async {
await for (final url in images()) {
imageUrls.insert(0, url);
_key.currentState?.insertItem(
0,
duration: Duration(milliseconds: 400),
);
}
}
@override
Widget build(BuildContext context) {
populateList();
return Scaffold(
appBar: AppBar(
title: Text('Animated Lists in Flutter'),
),
body: Padding(
padding: const EdgeInsets.all(8.0),
child: AnimatedList(
key: _key,
initialItemCount: imageUrls.length,
itemBuilder: (context, index, animation) {
final imageUrl = imageUrls[index];
return SizeTransition(
sizeFactor: animation.drive(
CurveTween(curve: Curves.elasticInOut),
),
child: Column(
children: [
NetworkImageCard(url: imageUrl),
SizedBox(height: 10.0),
],
),
);
},
),
),
);
}
}
CheckboxListTile in Flutter
import 'package:flutter/material.dart';
enum Item { umbrella, coat, boots }
extension Info on Item {
String get title {
switch (this) {
case Item.umbrella:
return 'Umbrella';
case Item.boots:
return 'Boots';
case Item.coat:
return 'Jacket';
}
}
String get icon {
switch (this) {
case Item.umbrella:
return '☂️';
case Item.boots:
return '🥾';
case Item.coat:
return '🧥';
}
}
}
typedef OnChecked = void Function(bool);
class Tile extends StatelessWidget {
final Item item;
final bool isChecked;
final OnChecked onChecked;
const Tile({
Key? key,
required this.item,
required this.isChecked,
required this.onChecked,
}) : super(key: key);
@override
Widget build(BuildContext context) {
return ConstrainedBox(
constraints: BoxConstraints(minHeight: 100.0),
child: Center(
child: CheckboxListTile(
shape: ContinuousRectangleBorder(),
value: isChecked,
secondary: Text(
item.icon,
style: TextStyle(fontSize: 30.0),
),
title: Text(
item.title,
style: TextStyle(fontSize: 40.0),
),
onChanged: (value) {
onChecked(value ?? false);
},
),
),
);
}
}
class HomePage extends StatefulWidget {
const HomePage({Key? key}) : super(key: key);
@override
State<HomePage> createState() => _HomePageState();
}
class _HomePageState extends State<HomePage> {
final Set<Item> _enabledItems = {};
Widget get listView {
return ListView.builder(
shrinkWrap: true,
itemBuilder: (context, index) {
final item = Item.values[index];
final isChecked = _enabledItems.contains(item);
return Tile(
isChecked: isChecked,
item: item,
onChecked: (isChecked) {
setState(() {
if (isChecked) {
_enabledItems.add(item);
} else {
_enabledItems.remove(item);
}
});
},
);
},
itemCount: Item.values.length,
);
}
Widget get title {
return Padding(
padding: const EdgeInsets.all(8.0),
child: Text(
"Remember to pick all items! It's going to be rainy today!",
textAlign: TextAlign.center,
style: TextStyle(fontSize: 40),
),
);
}
Widget get readyButton {
final onPressed = () async {
// program this
await showDialog(
context: context,
builder: (context) {
return AlertDialog(
content: Text('You seem to be ready for a rainy day! ✅'),
actions: [
TextButton(
onPressed: () {
Navigator.of(context).pop();
},
child: Text('OK'),
)
],
);
},
);
};
final isEnabled = _enabledItems.containsAll(Item.values);
return FractionallySizedBox(
widthFactor: 0.8,
child: ElevatedButton(
onPressed: isEnabled ? onPressed : null,
child: Text('Ready!'),
),
);
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('Checkbox List Tile in Flutter'),
),
body: SingleChildScrollView(
child: Column(
children: [
title,
listView,
SizedBox(height: 50.0),
readyButton,
],
),
),
);
}
}
- Operator on String in Dart
extension Minus on String {
String operator -(String rhs) => replaceAll(rhs, '');
}
void testIt() {
assert('foo bar' - 'foo ' == 'bar');
assert('foo bar foo' - 'foo' == ' bar ');
assert('bar' - 'foo' == 'bar');
assert('BAR' - 'bar' == 'BAR');
assert('foo' - 'FOO' == 'foo');
assert('foobarbaz' - 'bar' == 'foobaz');
}
Dart Progress for Future<T>
import 'dart:io' show stdout;
import 'dart:async' show Future, Stream;
const loadingSequence = ['⢿', '⣻', '⣽', '⣾', '⣷', '⣯', '⣟', '⡿'];
const escape = '\x1B[38;5;';
const color = '${escape}1m';
const textColor = '${escape}6m';
String progress({required int value, required String text}) {
final progress = '$color${loadingSequence[value % loadingSequence.length]}';
final coloredText = '$textColor$text';
return '$progress\t$coloredText';
}
Future<T> performWithProgress<T>({
required Future<T> task,
required String progressText,
}) {
final stream = Stream<String>.periodic(
Duration(milliseconds: 100),
(value) => progress(
value: value,
text: progressText,
),
);
final subscription = stream.listen(
(event) {
stdout.write('\r $event');
},
);
task.whenComplete(() {
stdout.write('\r ✅\t$progressText');
stdout.write('\n');
subscription.cancel();
});
return task;
}
final task1 = Future.delayed(Duration(seconds: 1), () => 'Result 1');
final task2 = Future.delayed(Duration(seconds: 2), () => 'Result 2');
final task3 = Future.delayed(Duration(seconds: 3), () => 'Result 3');
void main(List<String> args) async {
var result = await performWithProgress(
task: task1,
progressText: 'Loading task 1',
);
print('\tTask 1 result: $result');
result = await performWithProgress(
task: task2,
progressText: 'Loading task 2',
);
print('\tTask 2 result: $result');
result = await performWithProgress(
task: task3,
progressText: 'Loading task 3',
);
print('\tTask 3 result: $result');
}
Move Widget Shadows with Animation
import 'package:flutter/material.dart';
class ImageTransition extends AnimatedWidget {
final String imageUrl;
Animation<double> get shadowXOffset => listenable as Animation<double>;
const ImageTransition(this.imageUrl, {shadowXOffset})
: super(listenable: shadowXOffset);
@override
Widget build(BuildContext context) {
return Container(
clipBehavior: Clip.antiAlias,
decoration: BoxDecoration(
borderRadius: BorderRadius.circular(20.0),
boxShadow: [
BoxShadow(
blurRadius: 10,
offset: Offset(shadowXOffset.value, 20.0),
color: Colors.black.withAlpha(100),
spreadRadius: -10,
)
],
),
child: Image.network(imageUrl),
);
}
}
class HomePage extends StatefulWidget {
const HomePage({Key? key}) : super(key: key);
@override
State<HomePage> createState() => _HomePageState();
}
class CustomCurve extends CurveTween {
CustomCurve() : super(curve: Curves.easeInOutSine);
@override
double transform(double t) {
return (super.transform(t) - 0.5) * 25.0;
}
}
class _HomePageState extends State<HomePage>
with SingleTickerProviderStateMixin {
late final AnimationController _controller;
late final Animation<double> _animation;
@override
void initState() {
_controller = AnimationController(
vsync: this,
duration: Duration(seconds: 1),
);
_animation = CustomCurve().animate(_controller);
super.initState();
}
@override
void dispose() {
_controller.dispose();
super.dispose();
}
@override
Widget build(BuildContext context) {
_controller.repeat(reverse: true);
return Scaffold(
body: Padding(
padding: const EdgeInsets.all(8.0),
child: Center(
child: ImageTransition(
'https://bit.ly/3x7J5Qt',
shadowXOffset: _animation,
),
),
),
);
}
}
Gallery with Blurred Backgrounds in Flutter
import 'package:flutter/material.dart';
const images = [
'https://bit.ly/3x7J5Qt',
'https://bit.ly/3ywI8l6',
'https://bit.ly/36fNNj9',
'https://bit.ly/3jOueGG',
'https://bit.ly/3qYOtDm',
'https://bit.ly/3wt11Ec',
'https://bit.ly/3yvFg7X',
'https://bit.ly/3ywzOla',
'https://bit.ly/3wnASpW',
'https://bit.ly/3jXSDto',
];
class HomePage extends StatelessWidget {
const HomePage({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
return Scaffold(
body: PageView.builder(
scrollDirection: Axis.horizontal,
itemCount: images.length,
itemBuilder: (context, index) {
return WithBlurredBackground(imageUrl: images[index]);
},
),
);
}
}
class WithBlurredBackground extends StatelessWidget {
final String imageUrl;
const WithBlurredBackground({Key? key, required this.imageUrl})
: super(key: key);
@override
Widget build(BuildContext context) {
return SizedBox.expand(
child: Stack(
alignment: Alignment.center,
fit: StackFit.passthrough,
children: [
SizedBox.expand(
child: ClipRect(
child: ImageFiltered(
imageFilter: ImageFilter.blur(
sigmaX: 10.0,
sigmaY: 10.0,
),
child: Image.network(
imageUrl,
fit: BoxFit.fitHeight,
),
),
),
),
Image.network(imageUrl),
],
),
);
}
}
Custom Path Clippers in Flutter
import 'package:flutter/material.dart';
const images = [
'https://bit.ly/3x7J5Qt',
'https://bit.ly/3ywI8l6',
'https://bit.ly/36fNNj9',
'https://bit.ly/3jOueGG',
'https://bit.ly/3qYOtDm',
'https://bit.ly/3wt11Ec',
'https://bit.ly/3yvFg7X',
'https://bit.ly/3ywzOla',
'https://bit.ly/3wnASpW',
'https://bit.ly/3jXSDto',
];
class HomePage extends StatelessWidget {
const HomePage({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
return Scaffold(
body: SingleChildScrollView(
child: Padding(
padding: const EdgeInsets.only(
top: 40.0,
left: 10.0,
right: 10.0,
),
child: Column(
children: images
.map((url) => ElevatedNetworkImage(url: url))
.expand(
(img) => [
img,
SizedBox(height: 30.0),
],
)
.toList(),
),
),
),
);
}
}
class ElevatedNetworkImage extends StatelessWidget {
final String url;
const ElevatedNetworkImage({Key? key, required this.url}) : super(key: key);
@override
Widget build(BuildContext context) {
return PhysicalShape(
color: Colors.white,
clipper: Clipper(),
elevation: 20.0,
clipBehavior: Clip.none,
shadowColor: Colors.white.withAlpha(200),
child: CutEdges(
child: Image.network(url),
),
);
}
}
class Clipper extends CustomClipper<Path> {
static const variance = 0.2;
static const reverse = 1.0 - variance;
@override
Path getClip(Size size) {
final path = Path();
path.moveTo(0.0, size.height * Clipper.variance);
path.lineTo(size.width * Clipper.variance, 0.0);
path.lineTo(size.width, 0.0);
path.lineTo(size.width, size.height * Clipper.reverse);
path.lineTo(size.width * Clipper.reverse, size.height);
path.lineTo(0.0, size.height);
path.lineTo(0.0, size.height * Clipper.variance);
path.close;
return path;
}
@override
bool shouldReclip(covariant CustomClipper<Path> oldClipper) => false;
}
class CutEdges extends StatelessWidget {
final Widget child;
const CutEdges({Key? key, required this.child}) : super(key: key);
@override
Widget build(BuildContext context) {
return ClipPath(
clipper: Clipper(),
child: child,
);
}
}
Frost Effect on Images in Flutter
import 'package:flutter/material.dart';
const images = [
'https://bit.ly/3x7J5Qt',
'https://bit.ly/3ywI8l6',
'https://bit.ly/36fNNj9',
'https://bit.ly/3jOueGG',
'https://bit.ly/3qYOtDm',
'https://bit.ly/3wt11Ec',
'https://bit.ly/3yvFg7X',
'https://bit.ly/3ywzOla',
'https://bit.ly/3wnASpW',
'https://bit.ly/3jXSDto',
];
final loremIpsum =
'Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.';
class HomePage extends StatelessWidget {
const HomePage({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
return Scaffold(
body: Center(
child: Padding(
padding: const EdgeInsets.fromLTRB(
8.0,
0.0,
8.0,
0.0,
),
child: SingleChildScrollView(
child: Column(
children: images
.map(
(url) => GlossyNetworkImageWithProgress(
url: url,
title: 'Image title',
description: loremIpsum,
),
)
.expand(
(image) => [
image,
SizedBox(height: 16.0),
],
)
.toList(),
),
),
),
),
);
}
}
class GlossyNetworkImageWithProgress extends StatefulWidget {
final String url;
final String title;
final String description;
const GlossyNetworkImageWithProgress(
{Key? key,
required this.url,
required this.title,
required this.description})
: super(key: key);
@override
_GlossyNetworkImageWithProgressState createState() =>
_GlossyNetworkImageWithProgressState();
}
class _GlossyNetworkImageWithProgressState
extends State<GlossyNetworkImageWithProgress>
with SingleTickerProviderStateMixin {
late final AnimationController _controller;
late final Animation<double> _animation;
@override
void initState() {
super.initState();
_controller = AnimationController(
vsync: this,
duration: Duration(seconds: 1),
);
_animation = Tween(
begin: 0.0,
end: 1.0,
).animate(_controller);
}
@override
void dispose() {
_controller.dispose();
super.dispose();
}
@override
Widget build(BuildContext context) {
final networkImage = Image.network(
widget.url,
fit: BoxFit.fitHeight,
frameBuilder: (context, child, frame, wasSynchronouslyLoaded) {
_controller.reset();
_controller.forward();
return FadeTransition(
opacity: _animation,
child: CustomBox(
child: child,
),
);
},
loadingBuilder: (context, child, loadingProgress) {
final totalBytes = loadingProgress?.expectedTotalBytes;
final bytesLoaded = loadingProgress?.cumulativeBytesLoaded;
if (totalBytes != null && bytesLoaded != null) {
return CustomBox(
child: CircularProgressIndicator(
backgroundColor: Colors.white70,
value: bytesLoaded / totalBytes,
color: Colors.blue[900],
strokeWidth: 5.0,
),
);
} else {
return child;
}
},
errorBuilder: (context, error, stackTrace) {
return Text('Error!');
},
);
return BottomGloss(
networkImage: networkImage,
title: widget.title,
description: widget.description,
);
}
}
class BottomGloss extends StatelessWidget {
final String title;
final String description;
const BottomGloss(
{Key? key,
required this.networkImage,
required this.title,
required this.description})
: super(key: key);
final Image networkImage;
@override
Widget build(BuildContext context) {
return ClipRRect(
borderRadius: BorderRadius.all(Radius.circular(8.0)),
child: Stack(
fit: StackFit.passthrough,
children: [
networkImage,
Container(
height: 300.0,
alignment: Alignment.bottomCenter,
child: ClipRect(
child: FractionallySizedBox(
heightFactor: 0.5,
child: BackdropFilter(
filter: ImageFilter.blur(
sigmaX: 10.0,
sigmaY: 10.0,
),
child: BottomContents(
title: title,
description: description,
),
),
),
),
),
],
),
);
}
}
class BottomContents extends StatelessWidget {
final String title;
final String description;
const BottomContents({
Key? key,
required this.title,
required this.description,
}) : super(key: key);
@override
Widget build(BuildContext context) {
return Container(
color: Colors.white.withOpacity(0.4),
child: Padding(
padding: const EdgeInsets.all(8.0),
child: SingleChildScrollView(
child: Column(
crossAxisAlignment: CrossAxisAlignment.start,
children: [
TitleText(text: title),
SizedBox(height: 8.0),
SubTitleText(text: description),
],
),
),
),
);
}
}
class SubTitleText extends StatelessWidget {
final String text;
const SubTitleText({Key? key, required this.text}) : super(key: key);
@override
Widget build(BuildContext context) {
return Text(
text,
style: TextStyle(
color: Colors.black,
fontSize: 20.0,
),
);
}
}
class TitleText extends StatelessWidget {
final String text;
const TitleText({Key? key, required this.text}) : super(key: key);
@override
Widget build(BuildContext context) {
return Text(
text,
style: TextStyle(
color: Colors.white,
fontSize: 30.0,
),
);
}
}
class CustomBox extends StatelessWidget {
final Widget child;
const CustomBox({Key? key, required this.child}) : super(key: key);
@override
Widget build(BuildContext context) {
return SizedBox(
height: 300.0,
width: MediaQuery.of(context).size.width,
child: child is ProgressIndicator ? Center(child: child) : child,
);
}
}
Custom Clippers in Flutter
import 'package:flutter/material.dart';
import 'dart:math' show min;
const gridImages = [
'https://bit.ly/3x7J5Qt',
'https://bit.ly/3ywI8l6',
'https://bit.ly/3jRSRCu',
'https://bit.ly/36fNNj9',
'https://bit.ly/3jOueGG',
'https://bit.ly/3qYOtDm',
'https://bit.ly/3wt11Ec',
'https://bit.ly/3yvFg7X',
'https://bit.ly/3ywzOla',
'https://bit.ly/3wnASpW',
'https://bit.ly/3jXSDto',
];
class HomePage extends StatelessWidget {
const HomePage({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
return Scaffold(
body: GridView.count(
padding: const EdgeInsets.fromLTRB(8.0, 48.0, 8.0, 48.0),
crossAxisCount: 2,
mainAxisSpacing: 8.0,
crossAxisSpacing: 8.0,
children: gridImages
.map((url) => NetworkImageWithProgress(url: url))
.toList(),
),
);
}
}
class CircularClipper extends CustomClipper<Rect> {
@override
Rect getClip(Size size) {
final center = Offset(
size.width / 2.0,
size.height / 2.0,
);
final minWidthorHeight = min(size.width, size.height);
return Rect.fromCenter(
center: center,
width: minWidthorHeight,
height: minWidthorHeight,
);
}
@override
bool shouldReclip(covariant CustomClipper<Rect> oldClipper) => false;
}
class Circular extends StatelessWidget {
final Widget child;
const Circular({Key? key, required this.child}) : super(key: key);
@override
Widget build(BuildContext context) {
return ClipOval(
clipper: CircularClipper(),
child: child,
);
}
}
class CustomBox extends StatelessWidget {
final Widget child;
const CustomBox({Key? key, required this.child}) : super(key: key);
@override
Widget build(BuildContext context) {
return SizedBox(
height: 220.0,
width: MediaQuery.of(context).size.width,
child: child is ProgressIndicator
? Center(child: child)
: Circular(child: child),
);
}
}
class NetworkImageWithProgress extends StatefulWidget {
final String url;
const NetworkImageWithProgress({Key? key, required this.url})
: super(key: key);
@override
_NetworkImageWithProgressState createState() =>
_NetworkImageWithProgressState();
}
class _NetworkImageWithProgressState extends State<NetworkImageWithProgress>
with SingleTickerProviderStateMixin {
late final AnimationController _controller;
late final Animation<double> _animation;
@override
void initState() {
super.initState();
_controller = AnimationController(
vsync: this,
duration: Duration(seconds: 1),
);
_animation = Tween(
begin: 0.0,
end: 1.0,
).animate(_controller);
}
@override
void dispose() {
_controller.dispose();
super.dispose();
}
@override
Widget build(BuildContext context) {
return Image.network(
widget.url,
fit: BoxFit.fitHeight,
frameBuilder: (context, child, frame, wasSynchronouslyLoaded) {
_controller.reset();
_controller.forward();
return FadeTransition(
opacity: _animation,
child: CustomBox(
child: child,
),
);
},
loadingBuilder: (context, child, loadingProgress) {
final totalBytes = loadingProgress?.expectedTotalBytes;
final bytesLoaded = loadingProgress?.cumulativeBytesLoaded;
if (totalBytes != null && bytesLoaded != null) {
return CustomBox(
child: CircularProgressIndicator(
backgroundColor: Colors.white70,
value: bytesLoaded / totalBytes,
color: Colors.blue[900],
strokeWidth: 5.0,
),
);
} else {
return child;
}
},
errorBuilder: (context, error, stackTrace) {
return Text('Error!');
},
);
}
}
Check if Website is Up or Down in Dart
class UpStatus {
final bool isUp;
final DateTime timestamp;
const UpStatus(this.isUp, this.timestamp);
}
class Pling {
final String url;
final Duration interval;
const Pling({
required this.url,
required this.interval,
});
Stream<UpStatus> checkIfUp() =>
Stream.periodic(interval, (_) => DateTime.now()).asyncExpand(
(now) => HttpClient()
.headUrl(Uri.parse(url))
.then((req) => req..followRedirects = false)
.then((req) => req.close())
.then((resp) => resp.statusCode)
.then((statusCode) => statusCode == 200)
.onError((error, stackTrace) => false)
.then((isUp) => UpStatus(isUp, now))
.asStream(),
);
}
const oneSecond = Duration(seconds: 1);
const url = 'https://dart.dev';
extension IsOrIsNot on bool {
String get isOrIsNot => this ? 'is' : 'is not';
}
void testIt() async {
final pling = Pling(
url: url,
interval: oneSecond,
);
await for (final upStatus in pling.checkIfUp()) {
final timestamp = upStatus.timestamp;
final isUpStr = upStatus.isUp.isOrIsNot;
print('$url $isUpStr up at $timestamp');
}
}
Section Titles on ListView in Flutter
import 'package:flutter/material.dart';
final List<Section> allSections = [
Section(
'Spring',
[
'https://cnn.it/3xu58Ap',
'https://bit.ly/3ueqqC1',
],
),
Section(
'Summer',
[
'https://bit.ly/3ojNhLc',
'https://bit.ly/2VcCSow',
],
),
Section(
'Autumn',
[
'https://bit.ly/3ib1TJk',
'https://bit.ly/2XSpjvq',
],
),
Section(
'Winter',
[
'https://bit.ly/3iaQNE7',
'https://bit.ly/3AY8YE4',
],
),
];
class Section {
final String title;
final List<String> urls;
const Section(this.title, this.urls);
}
extension ToWidgets on Section {
Iterable<Widget> toNetworkImageCards() {
return [
Padding(
padding: const EdgeInsets.all(8.0),
child: Text(
title,
style: TextStyle(
fontSize: 40,
),
),
),
...urls.expand(
(url) => [
NetworkImageCard(url: url),
SizedBox(height: 10),
],
),
];
}
}
class NetworkImageCard extends StatelessWidget {
final String url;
const NetworkImageCard({
Key? key,
required this.url,
}) : super(key: key);
@override
Widget build(BuildContext context) {
return Center(
child: Container(
child: NetworkImageWithProgress(
url: url,
),
),
);
}
}
class NetworkImageWithProgress extends StatefulWidget {
final String url;
const NetworkImageWithProgress({Key? key, required this.url})
: super(key: key);
@override
_NetworkImageWithProgressState createState() =>
_NetworkImageWithProgressState();
}
class _NetworkImageWithProgressState extends State<NetworkImageWithProgress>
with SingleTickerProviderStateMixin {
late final AnimationController _controller;
late final Animation<double> _animation;
@override
void initState() {
super.initState();
_controller = AnimationController(
vsync: this,
duration: Duration(seconds: 1),
);
_animation = Tween(
begin: 0.0,
end: 1.0,
).animate(_controller);
}
@override
void dispose() {
_controller.dispose();
super.dispose();
}
@override
Widget build(BuildContext context) {
return Image.network(
widget.url,
fit: BoxFit.fitWidth,
frameBuilder: (context, child, frame, wasSynchronouslyLoaded) {
_controller.reset();
_controller.forward();
return FadeTransition(
opacity: _animation,
child: CustomBox(
child: child,
),
);
},
loadingBuilder: (context, child, loadingProgress) {
final totalBytes = loadingProgress?.expectedTotalBytes;
final bytesLoaded = loadingProgress?.cumulativeBytesLoaded;
if (totalBytes != null && bytesLoaded != null) {
return CustomBox(
child: CircularProgressIndicator(
backgroundColor: Colors.white70,
value: bytesLoaded / totalBytes,
color: Colors.blue[900],
strokeWidth: 5.0,
),
);
} else {
return child;
}
},
errorBuilder: (context, error, stackTrace) {
return Text('Error!');
},
);
}
}
class CustomBox extends StatelessWidget {
final Widget child;
const CustomBox({Key? key, required this.child}) : super(key: key);
@override
Widget build(BuildContext context) {
return SizedBox(
height: 220.0,
width: MediaQuery.of(context).size.width,
child: child is ProgressIndicator ? Center(child: child) : child,
);
}
}
class HomePage extends StatelessWidget {
const HomePage({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
return Scaffold(
body: ListView.builder(
itemBuilder: (context, index) {
final section = allSections[index];
return Column(
crossAxisAlignment: CrossAxisAlignment.start,
children: section.toNetworkImageCards().toList(),
);
},
itemCount: allSections.length,
),
);
}
}
Circular Progress in Flutter
import 'package:flutter/material.dart';
class CustomBox extends StatelessWidget {
final Widget child;
const CustomBox({Key? key, required this.child}) : super(key: key);
@override
Widget build(BuildContext context) {
return SizedBox(
height: 220.0,
width: MediaQuery.of(context).size.width,
child: Center(child: child),
);
}
}
class NetworkImageWithProgress extends StatefulWidget {
final String url;
const NetworkImageWithProgress({Key? key, required this.url})
: super(key: key);
@override
_NetworkImageWithProgressState createState() =>
_NetworkImageWithProgressState();
}
class _NetworkImageWithProgressState extends State<NetworkImageWithProgress>
with SingleTickerProviderStateMixin {
late final AnimationController _controller;
late final Animation<double> _animation;
@override
void initState() {
super.initState();
_controller = AnimationController(
vsync: this,
duration: Duration(seconds: 1),
);
_animation = Tween(
begin: 0.0,
end: 1.0,
).animate(_controller);
}
@override
void dispose() {
_controller.dispose();
super.dispose();
}
@override
Widget build(BuildContext context) {
return Image.network(
widget.url,
fit: BoxFit.fitWidth,
frameBuilder: (context, child, frame, wasSynchronouslyLoaded) {
_controller.reset();
_controller.forward();
return FadeTransition(
opacity: _animation,
child: CustomBox(
child: child,
),
);
},
loadingBuilder: (context, child, loadingProgress) {
final totalBytes = loadingProgress?.expectedTotalBytes;
final bytesLoaded = loadingProgress?.cumulativeBytesLoaded;
if (totalBytes != null && bytesLoaded != null) {
return CustomBox(
child: CircularProgressIndicator(
backgroundColor: Colors.white70,
value: bytesLoaded / totalBytes,
color: Colors.blue[900],
strokeWidth: 5.0,
),
);
} else {
return child;
}
},
errorBuilder: (context, error, stackTrace) {
return Text('Error!');
},
);
}
}
final images = [
'https://bit.ly/3x7J5Qt',
'https://bit.ly/3ywI8l6',
'https://bit.ly/36fNNj9',
'https://bit.ly/3jOueGG',
'https://bit.ly/3wt11Ec',
'https://bit.ly/3ywzOla',
].map((url) => NetworkImageWithProgress(url: url)).expand(
(element) => [
element,
SizedBox(
height: 10.0,
)
],
);
class HomePage extends StatefulWidget {
const HomePage({Key? key}) : super(key: key);
@override
_HomePageState createState() => _HomePageState();
}
class _HomePageState extends State<HomePage> {
@override
Widget build(BuildContext context) {
return Scaffold(
body: SingleChildScrollView(
child: Column(
children: images.toList(),
),
),
);
}
}
Displaying Scroll Wheels in Flutter
import 'package:flutter/material.dart';
class FadingNetworkImage extends StatefulWidget {
final String url;
const FadingNetworkImage({Key? key, required this.url}) : super(key: key);
@override
_FadingNetworkImageState createState() => _FadingNetworkImageState();
}
class _FadingNetworkImageState extends State<FadingNetworkImage>
with SingleTickerProviderStateMixin {
late final AnimationController _controller;
late final Animation<double> _animation;
@override
void initState() {
super.initState();
_controller =
AnimationController(vsync: this, duration: Duration(seconds: 1));
_animation = Tween(begin: 0.0, end: 1.0).animate(_controller);
}
@override
void dispose() {
_controller.dispose();
super.dispose();
}
@override
Widget build(BuildContext context) {
return Image.network(
widget.url,
frameBuilder: (context, child, frame, wasSynchronouslyLoaded) {
_controller.reset();
_controller.forward();
return FadeTransition(
opacity: _animation,
child: child,
);
},
loadingBuilder: (context, child, loadingProgress) {
final totalBytes = loadingProgress?.expectedTotalBytes;
final bytesLoaded = loadingProgress?.cumulativeBytesLoaded;
if (totalBytes != null && bytesLoaded != null) {
return LinearProgressIndicator(
value: bytesLoaded / totalBytes,
);
} else {
return child;
}
},
errorBuilder: (context, error, stackTrace) {
return Text('Error!');
},
);
}
}
final images = [
'https://bit.ly/3x7J5Qt',
'https://bit.ly/3ywI8l6',
'https://bit.ly/36fNNj9',
'https://bit.ly/3jOueGG',
'https://bit.ly/3wt11Ec',
'https://bit.ly/3ywzOla',
].map((i) => NetworkImageCard(url: i));
class NetworkImageCard extends StatelessWidget {
final String url;
const NetworkImageCard({
Key? key,
required this.url,
}) : super(key: key);
@override
Widget build(BuildContext context) {
return Center(
child: Container(
clipBehavior: Clip.antiAlias,
decoration: BoxDecoration(
borderRadius: BorderRadius.circular(20.0),
boxShadow: [
BoxShadow(
blurRadius: 5,
offset: Offset(0, 0),
color: Colors.black.withAlpha(40),
spreadRadius: 5,
)
],
),
child: FadingNetworkImage(
url: url,
),
),
);
}
}
class HomePage extends StatefulWidget {
const HomePage({Key? key}) : super(key: key);
@override
_HomePageState createState() => _HomePageState();
}
class _HomePageState extends State<HomePage> {
@override
Widget build(BuildContext context) {
return Scaffold(
body: ListWheelScrollView(
itemExtent: 164.0,
squeeze: 0.9,
perspective: 0.003,
children: images.toList(),
),
);
}
}
Post Messages to Slack with Dart
import 'dart:convert' show utf8;
import 'dart:convert' show json;
class SlackMessage {
final String? inChannel;
final String? userName;
final String message;
final String? iconEmoji;
const SlackMessage({
required this.inChannel,
required this.userName,
required this.message,
required this.iconEmoji,
});
Future<bool> send(String webhookUrl) async {
final payload = {
'text': message,
if (inChannel != null) 'channel': inChannel!,
if (userName != null) 'username': userName!,
if (iconEmoji != null) 'icon_emoji': iconEmoji!
};
final request = await HttpClient().postUrl(Uri.parse(webhookUrl));
final payloadData = utf8.encode(json.encode(payload));
request.add(payloadData);
final response = await request.close();
return response.statusCode == 200;
}
}
const webhookUrl = 'put your webhook url here';
void testIt() async {
final message = SlackMessage(
inChannel: 'dart',
userName: 'Flutter',
message: 'Hello from Dart in Terminal',
iconEmoji: 'blue_heart:',
);
if (await message.send(webhookUrl)) {
print('Successfully sent the message');
} else {
print('Could not send the message');
}
}
Unwrap List<T?>? in Dart
extension Unwrap<T> on List<T?>? {
List<T> unwrap() => (this ?? []).whereType<T>().toList();
}
void testOptionalListOfOptionals() {
final List<int?>? optionalListOfOptionals = [1, 2, null, 3, null];
final unwrapped = optionalListOfOptionals.unwrap(); // List<int>
print(unwrapped); // prints [1, 2, 3]
}
void testListOfOptionals() {
final listOfOptionals = [20, 30, null, 40]; // List<int?>
final unwrapped = listOfOptionals.unwrap(); // List<int>
print(unwrapped); // prints [20, 30, 40]
}
void testNormalList() {
final list = [50, 60, 70]; // List<int>
final unwrapped = list.unwrap(); // List<int>
print(unwrapped); // prints [50, 60, 70]
}
Avoiding UI Jitters When Switching Widgets in Flutter
const imageUrls = [
'https://cnn.it/3xu58Ap', // spring
'https://bit.ly/2VcCSow', // summer
'https://bit.ly/3A3zStC', // autumn
'https://bit.ly/2TNY7wi' // winter
];
extension ToNetworkImage<T extends String> on List<T> {
List<Widget> toNetworkImages() => map((s) => Image.network(s)).toList();
}
class HomePage extends StatefulWidget {
@override
State createState() => _HomePageState();
}
class _HomePageState extends State<HomePage> {
var _currentIndex = 0;
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(title: Text('Indexed Stack')),
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: [
IndexedStack(
index: _currentIndex,
children: imageUrls.toNetworkImages(),
),
TextButton(
onPressed: () {
setState(
() {
_currentIndex++;
if (_currentIndex >= imageUrls.length) {
_currentIndex = 0;
}
},
);
},
child: Text('Go to next season'),
)
],
),
),
);
}
}
Detect Redirects in Dart
Future<bool> doesRedirect(String url) => HttpClient()
.headUrl(Uri.parse(url))
.then((req) => req..followRedirects = false)
.then((req) => req.close())
.then((resp) => resp.statusCode)
.then((statusCode) => [301, 302, 303, 307, 308].contains(statusCode));
void testIt() async {
final test1 = await doesRedirect('https://cnn.it/3xu58Ap');
assert(test1 == true);
final test2 = await doesRedirect('https://dart.dev');
assert(test2 == false);
final test3 = await doesRedirect('https://bit.ly/2VcCSow');
assert(test3 == true);
}
Proportional Constraints in Flutter
class ProportionalWidthNetworkImage extends StatelessWidget {
final String url;
final double widthProportion;
const ProportionalWidthNetworkImage(
{Key? key, required this.url, required this.widthProportion})
: super(key: key);
@override
Widget build(BuildContext context) {
return LayoutBuilder(
builder: (context, constraints) {
return Image.network(
url,
loadingBuilder: (context, child, loadingProgress) {
final widget =
loadingProgress == null ? child : LinearProgressIndicator();
return Container(
width: constraints.maxWidth * widthProportion,
child: widget,
);
},
);
},
);
}
}
class HomePage extends StatelessWidget {
const HomePage({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
return Scaffold(
body: Center(
child: ProportionalWidthNetworkImage(
url: 'https://cnn.it/3xu58Ap',
widthProportion: 0.8,
),
),
);
}
}
Displaying Cupertino Action Sheets in Flutter
import 'package:flutter/cupertino.dart';
enum Season { spring, summer, autumn, winter }
extension Title on Season {
String get title => describeEnum(this).capitalized;
}
extension Caps on String {
String get capitalized => this[0].toUpperCase() + substring(1);
}
extension ToWidget on Season {
Widget toWidget() {
switch (this) {
case Season.spring:
return Image.network('https://cnn.it/3xu58Ap');
case Season.summer:
return Image.network('https://bit.ly/2VcCSow');
case Season.autumn:
return Image.network('https://bit.ly/3A3zStC');
case Season.winter:
return Image.network('https://bit.ly/2TNY7wi');
}
}
}
class HomePage extends StatefulWidget {
HomePage({Key? key}) : super(key: key);
@override
_HomePageState createState() => _HomePageState();
}
Future<Season> _chooseSeason(
BuildContext context,
Season currentSeason,
) async {
CupertinoActionSheet actionSheet(BuildContext context) {
return CupertinoActionSheet(
title: Text('Choose your favorite season:'),
actions: Season.values
.map(
(season) => CupertinoActionSheetAction(
onPressed: () {
Navigator.of(context).pop(season);
},
child: Text(season.title),
),
)
.toList(),
cancelButton: CupertinoActionSheetAction(
onPressed: () {
Navigator.of(context).pop(currentSeason);
},
child: Text('Cancel'),
),
);
}
return await showCupertinoModalPopup(
context: context,
builder: (context) => actionSheet(context),
);
}
class _HomePageState extends State<HomePage> {
var _season = Season.spring;
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(_season.title),
),
body: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: [
_season.toWidget(),
TextButton(
onPressed: () async {
_season = await _chooseSeason(
context,
_season,
);
setState(() {});
},
child: Text('Choose a season'),
),
],
),
);
}
}
Rotating List<T> in Dart
extension Rotate<T> on List<T> {
int _rotationTimes(int places) {
if (isEmpty) {
return 0;
}
if (places == 0) {
throw ArgumentError('places should be more than 0');
}
return places % length;
}
List<T> rotatedRight(int places) {
final times = _rotationTimes(places);
if (times == 0) {
return this;
} else {
final cutOff = length - times;
return sublist(cutOff)..addAll(sublist(0, cutOff));
}
}
List<T> rotatedLeft(int places) {
final times = _rotationTimes(places);
if (times == 0) {
return this;
} else {
return sublist(times)..addAll(sublist(0, times));
}
}
}
extension Equality<T extends Comparable> on List<T> {
bool isEqualTo(List<T> other) {
if (other.length != length) {
return false;
}
for (var i = 0; i < length; i++) {
if (other[i] != this[i]) {
return false;
}
}
return true;
}
}
const arr = [1, 2, 3];
void testIt() {
assert(arr.rotatedRight(1).isEqualTo([3, 1, 2]));
assert(arr.rotatedRight(2).isEqualTo([2, 3, 1]));
assert(arr.rotatedRight(3).isEqualTo([1, 2, 3]));
assert(arr.rotatedRight(4).isEqualTo([3, 1, 2]));
assert(arr.rotatedLeft(1).isEqualTo([2, 3, 1]));
assert(arr.rotatedLeft(2).isEqualTo([3, 1, 2]));
assert(arr.rotatedLeft(3).isEqualTo([1, 2, 3]));
assert(arr.rotatedLeft(4).isEqualTo([2, 3, 1]));
}
Displaying SnackBars in Flutter
class HomePage extends StatelessWidget {
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('Hello world'),
),
body: Center(
child: TextButton(
onPressed: () {
final now = DateFormat('kk:mm:ss').format(DateTime.now());
ScaffoldMessenger.of(context).removeCurrentSnackBar();
ScaffoldMessenger.of(context).showSnackBar(
SnackBar(
behavior: SnackBarBehavior.floating,
elevation: 5.0,
backgroundColor:
Colors.blue[600]!.withOpacity(0.8).withAlpha(200),
shape: RoundedRectangleBorder(
borderRadius: BorderRadius.circular(10),
side: BorderSide(
color: Colors.black.withOpacity(0.4),
width: 3.0,
),
),
content: Text('Some text $now'),
),
);
},
child: Text('Show toast'),
),
),
);
}
}
Custom Tab Bar Using ToggleButtons in Flutter
class TabBarButton extends StatelessWidget {
final IconData icon;
final double size;
const TabBarButton({Key? key, required this.icon, this.size = 60.0})
: super(key: key);
@override
Widget build(BuildContext context) {
return Padding(
padding: const EdgeInsets.all(8.0),
child: Icon(
icon,
size: size,
),
);
}
}
class HomePage extends StatelessWidget {
const HomePage({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('Toggle Buttons'),
),
body: Column(
children: [
CustomTabBar(),
],
),
);
}
}
class CustomTabBar extends StatefulWidget {
const CustomTabBar({Key? key}) : super(key: key);
@override
_CustomTabBarState createState() => _CustomTabBarState();
}
class _CustomTabBarState extends State<CustomTabBar> {
var _selection = [false, false, false];
@override
Widget build(BuildContext context) {
return Expanded(
child: Align(
alignment: FractionalOffset.bottomCenter,
child: SafeArea(
child: ToggleButtons(
isSelected: _selection,
onPressed: (index) {
setState(() {
_selection = List.generate(
_selection.length,
(i) => index == i ? true : false,
);
});
},
selectedColor: Colors.white,
fillColor: Colors.blue,
borderRadius: BorderRadius.circular(10.0),
borderWidth: 4.0,
borderColor: Colors.blue[400],
selectedBorderColor: Colors.blue,
highlightColor: Colors.blue.withOpacity(0.2),
children: [
TabBarButton(icon: Icons.settings),
TabBarButton(icon: Icons.add),
TabBarButton(icon: Icons.settings_remote)
],
),
),
),
);
}
}
Hashable Mixins in Dart
enum PetType { cat, dog }
mixin Pet {
String get name;
int get age;
PetType get type;
@override
String toString() => 'Pet ($type), name = $name, age = $age';
@override
int get hashCode => hashValues(name, age, type);
@override
bool operator ==(covariant Pet o) => o.hashCode == hashCode;
}
class Cat with Pet {
@override
final String name;
@override
final int age;
@override
final PetType type;
const Cat({required this.name, required this.age}) : type = PetType.cat;
}
void testIt() {
final cats = <Cat>{
Cat(name: 'Kitty 1', age: 2),
Cat(name: 'Kitty 2', age: 3),
Cat(name: 'Kitty 1', age: 2),
};
cats.forEach(print);
/* 👆🏻 prints the following:
Pet (PetType.cat), name = Kitty 1, age = 2
Pet (PetType.cat), name = Kitty 2, age = 3
*/
}
Flutter Tips and Tricks in Terminal
import 'dart:convert' show utf8;
import 'dart:io' show HttpClient, exit, Process, stderr;
import 'dart:math' show Random;
const rawBlobRoot =
'https://raw.githubusercontent.com/vandadnp/flutter-tips-and-tricks/main/';
void main(List<String> args) async {
final url = Uri.https('bit.ly', '/2V1GKsC');
try {
final client = HttpClient();
final images = await client
.getUrl(url)
.then((req) => req.close())
.then((resp) => resp.transform(utf8.decoder).join())
.then((body) => body.split('\n').map((e) => e.trim()))
.then((iter) => iter.toList())
.then((list) => list..retainWhere((s) => s.endsWith('.jpg)')))
.then((imageList) => imageList.map((e) => e.replaceAll('))
.then((imageList) => imageList.map((e) => e.replaceAll(')', '')))
.then((iter) => iter.toList());
final found = images[Random().nextInt(images.length)];
final result = '$rawBlobRoot$found';
await Process.run('open', [result]);
exit(0);
} catch (e) {
stderr.writeln('Could not proceed due to $e');
exit(1);
}
}
Searching List<List<T>> in Dart
const arr1 = [1, 2, 3];
const arr2 = [4, 5, 6];
const arr3 = [7, 8, 9];
const arr = [arr1, arr2, arr3];
extension FlattenFind<T extends Comparable> on Iterable<Iterable<T>> {
bool containsElement(T value) {
for (final arr in this) {
if (arr.contains(value)) {
return true;
}
}
return false;
}
}
void testIt() {
assert(arr.containsElement(2));
assert(arr.containsElement(8));
assert(!arr.containsElement(10));
assert(!arr.containsElement(10));
}
Cloning Objects in Dart
class Person {
final Map<String, Object> _values;
static const FIRST_NAME_KEY = 'FIRST_NAME';
static const LAST_NAME_KEY = 'LAST_NAME';
Person.from(Map<String, Object> props) : _values = props;
Person({
required String firstName,
required String lastName,
Map<String, Object>? props,
}) : _values = {
FIRST_NAME_KEY: firstName,
LAST_NAME_KEY: lastName,
};
@override
bool operator ==(covariant Person other) =>
other.firstName == firstName && other.lastName == lastName;
@override
String toString() => _values.toString();
}
extension Properties on Person {
String get firstName => _values[Person.FIRST_NAME_KEY].toString();
set firstName(String newValue) => _values[Person.FIRST_NAME_KEY] = newValue;
String get lastName => _values[Person.LAST_NAME_KEY].toString();
set lastName(String newValue) => _values[Person.LAST_NAME_KEY] = newValue;
}
extension Clone on Person {
Person clone([Map<String, Object>? additionalProps]) =>
Person.from(Map.from(_values)..addAll(additionalProps ?? {}));
}
extension Subscripts on Person {
Object? operator [](String key) => _values[key];
operator []=(String key, Object value) => _values[key] = value;
}
void testIt() {
final foo = Person(
firstName: 'Foo Firstname',
lastName: 'Foo Lastname',
);
print(foo); // {FIRST_NAME: Foo Firstname, LAST_NAME: Foo Lastname}
final copyOfFoo = foo.clone();
print(copyOfFoo); // {FIRST_NAME: Foo Firstname, LAST_NAME: Foo Lastname}
final bar = foo.clone({'age': 30});
print(bar); // {FIRST_NAME: Foo Firstname, LAST_NAME: Foo Lastname, age: 30}
assert(foo == copyOfFoo);
assert(foo == bar);
assert(foo['age'] == null);
assert(copyOfFoo['age'] == null);
assert(bar['age'] == 30);
}
Color Filters in Flutter
class HomePage extends StatefulWidget {
const HomePage({Key? key}) : super(key: key);
@override
_HomePageState createState() => _HomePageState();
}
class _HomePageState extends State<HomePage> {
var sliderValue = 0.0;
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('Color Filters in Flutter!'),
),
body: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: [
ColorFiltered(
colorFilter: ColorFilter.mode(
Colors.orange.withOpacity(sliderValue),
BlendMode.colorBurn,
),
child: Image.network('https://tinyurl.com/4vtvh35h'),
),
Slider(
value: sliderValue,
onChanged: (value) {
setState(() {
sliderValue = value;
});
},
)
],
),
);
}
}
Flattening Lists in Dart
class Person {
final String name;
const Person(this.name);
@override
String toString() => 'Person: $name';
}
class House {
final List<Person>? tennants;
final List<Person> builders;
const House({
required this.tennants,
required this.builders,
});
}
const houses = [
House(tennants: null, builders: [
Person('Builder 1'),
]),
House(tennants: [
Person('Tennant 1'),
Person('Tennant 2'),
], builders: [
Person('Builder 3')
]),
];
extension OptionalFlattend<T> on Iterable<List<T>?> {
Iterable<T> flattened() => expand((e) => e ?? []);
}
void testOptionalFlatten() {
final allTennants = houses.map((h) => h.tennants).flattened();
print(allTennants); // Person: Tennant 1, Person: Tennant 2
}
extension Flattend<T> on Iterable<List<T>> {
Iterable<T> flattened() => expand((e) => e);
}
void testNonOptionalFlatten() {
final allBuilders = houses.map((h) => h.builders).flattened();
print(allBuilders); // Person: Builder 1, Person: Builder 2
}
void testIt() {
testOptionalFlatten();
testNonOptionalFlatten();
}
Managing Duplicates in List<T> in Dart
extension Duplicates<T> on List<T> {
void addAllByAvoidingDuplicates(Iterable<T> values) =>
replaceRange(0, length, {
...([...this] + [...values])
});
int get numberOfDuplicates => length - {...this}.length;
bool get containsDuplicates => numberOfDuplicates > 0;
List<T> get uniques => [
...{...this}
];
void removeDuplicates() => replaceRange(
0,
length,
uniques,
);
List<T> get duplicates => [
for (var i = 0; i < length; i++)
[...this].skip(i + 1).contains(this[i]) ? this[i] : null
].whereType<T>().toList();
}
void testIt() {
final values = [3, 2, 10, 30, 40, 30, 100, 10];
assert(values.numberOfDuplicates == 2);
assert(values.containsDuplicates == true);
assert(values.uniques.length == values.length - 2);
print(values.uniques); // [3, 2, 10, 30, 40, 100]
values.removeDuplicates();
print(values); // [3, 2, 10, 30, 40, 100]
assert(values.numberOfDuplicates == 0);
assert(!values.containsDuplicates);
assert(values.duplicates.isEmpty);
values.addAllByAvoidingDuplicates([3, 2, 10, 200]);
print(values); // [3, 2, 10, 30, 40, 100, 200]
assert(values.containsDuplicates == false);
}
FlatMap and CompactMap in Dart
extension CompactMap<T> on List<T> {
List<E> compactMap<E>(E? Function(T element) f) {
Iterable<E> imp(E? Function(T element) f) sync* {
for (final value in this) {
final mapped = f(value);
if (mapped != null) {
yield mapped;
}
}
}
return imp(f).toList();
}
}
extension FlatMap<T> on T? {
E? flatMap<E>(E? Function(T value) f) {
if (this != null) {
return f(this!);
} else {
return null;
}
}
}
void testIt() {
final foo = [1, 2, null, 3, null, 4];
final bar = foo.compactMap((element) => element.flatMap((e) => e * 2));
print(bar); // prints 2, 4, 6, 8
}
Equality of List<T> in Dart
extension Equality<T extends Comparable> on List<T> {
bool isEqualTo(List<T> other) {
if (other.length != length) {
return false;
}
for (var i = 0; i < length; i++) {
if (other[i] != this[i]) {
return false;
}
}
return true;
}
}
int ascendingComparator<T extends Comparable>(T lhs, T rhs) =>
lhs.compareTo(rhs);
int descendingComparator<T extends Comparable>(T lhs, T rhs) =>
rhs.compareTo(lhs);
extension Sorted<T extends Comparable> on List<T> {
List<T> sorted({bool descending = false}) => descending
? ([...this]..sort(descendingComparator))
: ([...this]..sort(ascendingComparator));
}
void testIt() {
assert([1, 2, 3].isEqualTo([1, 2, 3]));
assert(![1, 2, 3].isEqualTo([1, 2, 2]));
assert([3, 1, 2].sorted().isEqualTo([1, 2, 3]));
assert(![3, 1, 2].sorted().isEqualTo([3, 1, 2]));
assert(['Foo', 'Bar', 'Baz'].isEqualTo(['Foo', 'Bar', 'Baz']));
assert(!['Foo', 'Bar', 'Baz'].isEqualTo(['foo', 'Bar', 'Baz']));
}
Constants in Dart
class Person {
final String name;
final int age;
const Person({required this.name, required this.age});
}
const foo = Person(name: 'Foo', age: 20);
const foo2 = Person(name: 'Foo', age: 20);
const bar = Person(name: 'Bar', age: 20);
void assert_eq(Object lhs, Object rhs) {
assert(lhs == rhs);
}
void assert_ne(Object lhs, Object rhs) {
assert(lhs != rhs);
}
void testIt() {
assert_eq(foo, foo2);
assert_ne(foo, bar);
assert_ne(foo2, bar);
}
Displaying Scrollable Bottom Sheets in Flutter
class HomePage extends StatelessWidget {
const HomePage({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(title: Text('Scrollable Sheet')),
body: DraggableScrollableSheet(
initialChildSize: 0.2,
minChildSize: 0.2,
maxChildSize: 0.8,
builder: (context, scrollController) {
return Container(
decoration: decoration(),
clipBehavior: Clip.antiAlias,
child: SingleChildScrollView(
controller: scrollController,
child: column(),
),
);
},
),
);
}
}
const urls = [
'https://tinyurl.com/4vtvh35h',
'https://tinyurl.com/pujhs55w',
'https://tinyurl.com/u5k7zueh',
];
List<Widget> imageWithLoremIpsum(String uri) => [
Image.network(uri),
SizedBox(height: 10),
loremIpsum(),
SizedBox(height: 10),
];
Column column() => Column(
children: imageWithLoremIpsum(urls[0]) +
imageWithLoremIpsum(urls[1]) +
imageWithLoremIpsum(urls[2]),
);
Text loremIpsum() => Text(
'Lorem ipsum ' * 10,
textAlign: TextAlign.center,
);
BoxDecoration decoration() => BoxDecoration(
border: Border.all(color: Colors.white),
borderRadius: BorderRadius.only(
topLeft: Radius.circular(10),
topRight: Radius.circular(10),
),
color: Colors.white70,
);
YouTube Ad Remover in Dart
import 'dart:io' show stdout, stderr, exitCode;
import 'package:collection/collection.dart' show IterableExtension;
// example argument: https://www.youtube.com/watch?v=mtETXtSP0pA
void main(List<String> args) async {
if (args.isEmpty) {
stdout.writeln('usage: dart youtube.dart "https://..."');
return;
}
final link =
args.firstWhereOrNull((element) => Uri.tryParse(element) != null);
if (link == null) {
stderr.writeln('No YouTube url found');
exitCode = 1;
return;
}
try {
final uri = Uri.parse(link);
if (uri.scheme.toLowerCase() != 'https' ||
uri.host.toLowerCase() != 'www.youtube.com' ||
uri.queryParameters['v'] == null) {
throw FormatException();
} else {
final videoId = uri.queryParameters['v'];
final embedUri = Uri.parse('${uri.scheme}://${uri.host}/embed/$videoId');
stdout.writeln(embedUri);
exitCode = 0;
}
} on FormatException catch (e) {
stderr.writeln('Invalid Uri, try again! err = $e');
exitCode = 1;
return;
}
}
Fade Between Widgets in Flutter
const urls = [
'https://bit.ly/3qYOtDm',
'https://bit.ly/3wt11Ec',
];
class HomePage extends StatefulWidget {
const HomePage({Key? key}) : super(key: key);
@override
_HomePageState createState() => _HomePageState();
}
class _HomePageState extends State<HomePage> {
var isShowingFirstImage = true;
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('AnimatedCrossFade in Flutter'),
),
body: Center(
child: AnimatedCrossFade(
layoutBuilder: (topChild, topChildKey, bottomChild, bottomChildKey) {
return GestureDetector(
onTap: () {
setState(() {
isShowingFirstImage = !isShowingFirstImage;
});
},
child: AnimatedCrossFade.defaultLayoutBuilder(
topChild, topChildKey, bottomChild, bottomChildKey),
);
},
firstChild: Image.network(urls[0]),
secondChild: Image.network(urls[1]),
crossFadeState: isShowingFirstImage
? CrossFadeState.showFirst
: CrossFadeState.showSecond,
duration: Duration(milliseconds: 400),
),
),
);
}
}
Sort Descriptors in Dart
int ascendingComparator<T extends Comparable>(T lhs, T rhs) =>
lhs.compareTo(rhs);
int descendingComparator<T extends Comparable>(T lhs, T rhs) =>
rhs.compareTo(lhs);
extension Sorted<T extends Comparable> on List<T> {
List<T> sorted({bool descending = false}) => descending
? (this..sort(descendingComparator))
: (this..sort(ascendingComparator));
}
class Person implements Comparable {
final int age;
final String name;
const Person({required this.age, required this.name});
@override
int compareTo(covariant Person other) => age.compareTo(other.age);
@override
String toString() => 'Person, name = $name ($age)';
}
void testIt() {
final people = [
Person(age: 39, name: 'Father Foo'),
Person(age: 40, name: 'Mother Bar'),
Person(age: 13, name: 'Son Baz'),
];
print('ascending sort');
people.sorted().forEach(print);
// prints Son Baz (13), Father Foo (39), Mother Bar (40)
print('descending sort');
people.sorted(descending: true).forEach(print);
// prints Mother Bar (40), Father Foo (39), Son Baz (13)
}
User Sortable Columns and Tables in Flutter
class Language {
final String name;
final Image image;
const Language(this.name, this.image);
Language.dart()
: name = 'Dart',
image = Image.network('https://bit.ly/3yH1Ivj');
Language.rust()
: name = 'Rust',
image = Image.network('https://bit.ly/3lPTqhb');
Language.python()
: name = 'Python',
image = Image.network('https://bit.ly/3iCFCEP');
Language.java()
: name = 'Java',
image = Image.network('https://bit.ly/3CCapJH');
static List<Language> all = [
Language.dart(),
Language.rust(),
Language.python(),
Language.java(),
];
}
extension Sort on List<Language> {
void sortByName(bool ascending) => sort((lhs, rhs) =>
ascending ? lhs.name.compareTo(rhs.name) : rhs.name.compareTo(lhs.name));
}
List<DataRow> rows(List<Language> langs) => langs
.map(
(l) => DataRow(
cells: [
DataCell(
Padding(
padding: const EdgeInsets.all(8.0),
child: l.image,
),
),
DataCell(Text(l.name)),
],
),
)
.toList();
class HomePage extends StatefulWidget {
const HomePage({Key? key}) : super(key: key);
@override
_HomePageState createState() => _HomePageState();
}
class _HomePageState extends State<HomePage> {
final List<Language> _langs = Language.all..sortByName(true);
int sortedColumnIndex = 1;
var isSortedAscending = true;
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(title: Text('WhatsApp')),
body: DataTable(
sortAscending: isSortedAscending,
sortColumnIndex: sortedColumnIndex,
columns: [
DataColumn(label: Text('Image')),
DataColumn(
label: Text('Name'),
onSort: (columnIndex, ascending) {
setState(() {
sortedColumnIndex = columnIndex;
isSortedAscending = ascending;
_langs.sortByName(ascending);
});
},
),
],
rows: rows(_langs),
),
);
}
}
Content-Length of List<Uri> in Dart
Recursive Dot Notation on Maps in Dart
final person = {
'firstName': 'Foo',
'lastName': 'Bar',
'age': 30,
'address': {
'street': {
'name': 'Baz street',
'numberOfHouses': 20,
},
'houseNumber': '#20',
'city': 'Stockholm',
'country': 'Sweden'
},
};
extension KeyPath on Map {
Object? valueFor({required String keyPath}) {
final keysSplit = keyPath.split('.');
final thisKey = keysSplit.removeAt(0);
final thisValue = this[thisKey];
if (keysSplit.isEmpty) {
return thisValue;
} else if (thisValue is Map) {
return thisValue.valueFor(keyPath: keysSplit.join('.'));
}
}
}
void testIt() {
assert(person.valueFor(keyPath: 'firstName') == 'Foo');
assert(person.valueFor(keyPath: 'age') == 30);
assert(person.valueFor(keyPath: 'address.street.name') == 'Baz street');
assert(person.valueFor(keyPath: 'address.houseNumber') == '#20');
}
Allow User Selection of Text in Flutter
const text = 'Flutter is an open-source UI software development'
' kit created by Google. It is used to develop cross platform applications'
' for Android, iOS, Linux, Mac, Windows, Google Fuchsia, '
'and the web from a single codebase.';
const imageUrl = 'https://bit.ly/3gT5Qk2';
class HomePage extends StatelessWidget {
const HomePage({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('Selectable Text in Flutter'),
),
body: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: [
Image.network(imageUrl),
SizedBox(height: 10.0),
Padding(
padding: const EdgeInsets.all(8.0),
child: SelectableText(
text,
textAlign: TextAlign.center,
showCursor: true,
cursorColor: Colors.blue,
toolbarOptions: ToolbarOptions(
copy: true,
selectAll: true,
),
style: TextStyle(
fontSize: 20,
fontWeight: FontWeight.w300,
),
),
),
],
),
);
}
}
Placing Constraints on Widgets in Flutter
const dashes = [
'https://bit.ly/3gHlTCU',
'https://bit.ly/3wOLO1c',
'https://bit.ly/3cXWD9j',
'https://bit.ly/3gT5Qk2',
];
class HomePage extends StatelessWidget {
const HomePage({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('ConstrainedBox in Flutter'),
),
body: InteractiveViewer(
minScale: 1.0,
maxScale: 2.0,
child: SingleChildScrollView(
scrollDirection: Axis.vertical,
child: Table(
defaultVerticalAlignment: TableCellVerticalAlignment.middle,
children: dashes
.map(
(dash) => TableRow(
children: [
ConstrainedBox(
constraints: BoxConstraints(
minHeight: 300,
),
child: Image.network(dash),
),
],
),
)
.toList(),
),
),
),
);
}
}
Animating Position Changes in Flutter
class HomePage extends StatefulWidget {
const HomePage({Key? key}) : super(key: key);
@override
_HomePageState createState() => _HomePageState();
}
class _HomePageState extends State<HomePage> {
var isMovedUp = false;
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(title: Text('AnimatedPositioned in Flutter')),
body: Center(
child: GestureDetector(
onTap: () => setState(() => isMovedUp = !isMovedUp),
child: Stack(
clipBehavior: Clip.none,
alignment: Alignment.center,
children: [
Image.network('https://bit.ly/2VcCSow'),
Text(
'Summer 😎',
style: TextStyle(
fontSize: 30,
color: Colors.black,
),
),
AnimatedPositioned(
duration: Duration(seconds: 1),
bottom: isMovedUp ? 140 : 10.0,
curve: Curves.elasticInOut,
child: CircleAvatar(
radius: 100,
backgroundImage: NetworkImage('https://bit.ly/3cXWD9j'),
backgroundColor: Colors.orange[300],
),
),
],
),
),
),
);
}
}
Transitioning Between Widgets in Flutter
enum Season { spring, summer, autumn, winter }
extension Caps on String {
String get capitalized => this[0].toUpperCase() + substring(1);
}
extension Title on Season {
String get title => describeEnum(this).capitalized;
}
class TitledImage {
final String title;
final Uri uri;
final ValueKey key;
const TitledImage(this.title, this.uri, this.key);
TitledImage.spring()
: title = Season.spring.title,
uri = Uri.https('cnn.it', '/3xu58Ap'),
key = ValueKey(1);
TitledImage.summer()
: title = Season.summer.title,
uri = Uri.https('bit.ly', '/2VcCSow'),
key = ValueKey(2);
TitledImage.autumn()
: title = Season.autumn.title,
uri = Uri.https('bit.ly', '/3A3zStC'),
key = ValueKey(3);
TitledImage.winter()
: title = Season.winter.title,
uri = Uri.https('bit.ly', '/2TNY7wi'),
key = ValueKey(4);
}
class HomePage extends StatefulWidget {
const HomePage({Key? key}) : super(key: key);
@override
_HomePageState createState() => _HomePageState();
}
class _HomePageState extends State<HomePage> {
var _img = TitledImage.summer();
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(title: Text(_img.title)),
body: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: [
AnimatedSwitcher(
switchInCurve: Curves.easeIn,
switchOutCurve: Curves.easeOut,
duration: Duration(milliseconds: 300),
transitionBuilder: (child, animation) {
return FadeTransition(opacity: animation, child: child);
},
child: Image.network(
_img.uri.toString(),
key: _img.key,
),
),
getButtons(),
],
),
);
}
Widget getButtons() {
return Row(
mainAxisAlignment: MainAxisAlignment.center,
children: [
TextButton(
onPressed: () => setState(() => _img = TitledImage.spring()),
child: Text(Season.spring.title),
),
TextButton(
onPressed: () => setState(() => _img = TitledImage.summer()),
child: Text(Season.summer.title),
),
TextButton(
onPressed: () => setState(() => _img = TitledImage.autumn()),
child: Text(Season.autumn.title),
),
TextButton(
onPressed: () => setState(() => _img = TitledImage.winter()),
child: Text(Season.winter.title),
),
],
);
}
}
Doubly Linked Lists in Dart
class Person extends LinkedListEntry<Person> {
final String name;
final int age;
Person({
required this.name,
required this.age,
});
@override
String toString() => 'Person name = $name, age = $age';
}
void testIt() {
final persons = LinkedList<Person>();
final dad = Person(name: 'Father Foo', age: 47);
final mom = Person(name: 'Mother Bar', age: 47);
final daughter = Person(name: 'Daughter Baz', age: 22);
persons.addAll([dad, mom, daughter]);
print(persons.first.previous); // null
print(persons.first); // Person name = Father Foo, age = 47
print(persons.first.next); // Person name = Mother Bar, age = 47
print(persons.last.previous); // Person name = Mother Bar, age = 47
print(persons.first.next?.next); // Person name = Daughter Baz, age = 22
print(persons.last.next); // null
}
Reordering Items Inside List Views in Flutter
class Item {
final Color color;
final String text;
final UniqueKey uniqueKey;
Item(this.color, this.text) : uniqueKey = UniqueKey();
}
extension ToListItem on Item {
Widget toListItem() => LimitedBox(
key: uniqueKey,
maxHeight: 200,
child: Container(
color: color,
child: Padding(
padding: const EdgeInsets.all(20),
child: Text(
text,
style: TextStyle(
color: Colors.white,
fontSize: 100,
),
),
),
),
);
}
class _HomePageState extends State<HomePage> {
var items = [
Item(Colors.deepPurple, 'Foo'),
Item(Colors.blueGrey, 'Bar'),
Item(Colors.lightGreen, 'Baz')
];
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('Reordered List View in Flutter'),
),
body: ReorderableListView(
onReorder: (oldIndex, newIndex) {
setState(() {
final item = items.removeAt(oldIndex);
items.insert(newIndex, item);
});
},
children: items.map((i) => i.toListItem()).toList(),
),
);
}
}
class HomePage extends StatefulWidget {
const HomePage({Key? key}) : super(key: key);
@override
_HomePageState createState() => _HomePageState();
}
Custom Stream Transformers in Dart
in this example we have created our own string transformer that
can trim a Stream<String> by trimming whitespace from both
beginning and end of the string
*/
import 'dart:convert' show utf8;
class StringTrimmer extends StreamTransformerBase<String, String> {
const StringTrimmer();
@override
Stream<String> bind(Stream<String> stream) =>
Stream.fromFuture(stream.join(' ')).map((str) => str.trim());
}
final string =
''' A long line of text with spaces in the beginning and the end,
divided into three lines just for the purpose of this demonstration ''';
void testIt() async {
final bytes = utf8.encode(string);
final result = await Stream.value(bytes)
.transform(utf8.decoder)
.transform(LineSplitter())
.transform(StringTrimmer())
.join();
print(result);
}
Expanding Stream Elements in Dart
/*
in this example we expand every element inside our Stream<int> to
a stream that in turn contains n+1 elements where n is the index generated
by our main stream, that's to say, 0, 1, 2, 3, 4, etc
*/
Stream<int> nestedEvents(int count) {
return Stream.periodic(
Duration(seconds: 1),
(e) => e,
).take(count).asyncExpand(
(i) => Stream.fromIterable(
Iterable.generate(i + 1),
),
);
}
void testIt() async {
/*
prints the followings in this order
0, 1
0, 1, 2
0, 1, 2, 3
0, 1, 2, 3, 4
*/
await for (final value in nestedEvents(5)) {
print('Value is $value');
}
}
Consume Streams for a Duration in Dart
extension TakeFor<T> on Stream<T> {
Stream<T> takeFor(Duration duration) {
final upTo = DateTime.now().add(duration);
return takeWhile((_) {
final now = DateTime.now();
return now.isBefore(upTo) | now.isAtSameMomentAs(upTo);
});
}
}
Stream<DateTime> source() => Stream.periodic(
Duration(milliseconds: 500),
(_) => DateTime.now(),
);
void testIt() async {
await for (final dateTime in source().takeFor(
Duration(seconds: 4),
)) {
print('date time is $dateTime');
}
}
Shortening URLs in Dart
import 'dart:convert' show json;
Future<Uri> shortenUri(Uri uri, String bitlyToken) async {
final client = HttpClient();
final endpoint = Uri.https('api-ssl.bitly.com', '/v4/shorten');
final response = await client.postUrl(endpoint).then(
(req) {
req.headers
..set(HttpHeaders.contentTypeHeader, 'application/json')
..set(HttpHeaders.authorizationHeader, 'Bearer $bitlyToken');
final body = {
'long_url': uri.toString(),
'domain': 'bit.ly',
};
final bodyBytes = utf8.encode(json.encode(body));
req.add(bodyBytes);
return req.close();
},
);
final responseBody = await response.transform(utf8.decoder).join();
final responseJson = json.decode(responseBody) as Map<String, dynamic>;
return Uri.parse(responseJson['link']);
}
void testIt() async {
print(await shortenUri(
Uri.parse('https://pixolity.se'),
'XXX',
));
}
LimitedBox Widget as ListView Items in Flutter
const images = [
'https://bit.ly/3x7J5Qt',
'https://bit.ly/3ywI8l6',
'https://bit.ly/3jRSRCu',
'https://bit.ly/36fNNj9',
'https://bit.ly/3jOueGG',
'https://bit.ly/3qYOtDm',
'https://bit.ly/3wt11Ec',
'https://bit.ly/3yvFg7X',
'https://bit.ly/3ywzOla',
'https://bit.ly/3wnASpW',
'https://bit.ly/3jXSDto',
];
extension ToListItemImage on String {
Widget toListItemImage() {
return LimitedBox(
maxHeight: 150.0,
child: Image.network(
this,
fit: BoxFit.fitWidth,
),
);
}
}
class HomePage extends StatelessWidget {
const HomePage({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(title: Text('Limited Box in Flutter')),
body: ListView(
children: images.map((str) => str.toListItemImage()).toList(),
),
);
}
}
Generically Convert Anything to Int in Dart
extension ToInt on Object {
int toInt() {
final list = [
if (this is Iterable<Object>)
...(List.of(this as Iterable<Object>))
else if (this is int)
[this as int]
else
(double.tryParse(toString()) ?? 0.0).round()
];
return list
.map((e) => (double.tryParse(e.toString()) ?? 0.0).round())
.reduce((lhs, rhs) => lhs + rhs);
}
}
void testIt() {
assert(1.toInt() == 1);
assert((2.2).toInt() == 2);
assert((2.0).toInt() == 2);
assert('3'.toInt() == 3);
assert(['4', '5'].toInt() == 9);
assert([4, 5].toInt() == 9);
assert(['2.4', '3.5'].toInt() == 6);
assert(['2', '3.5'].toInt() == 6);
assert({'2', 3, '4.2'}.toInt() == 9);
assert(['2', 3, '4.2', 5.3].toInt() == 14);
}
Validating URL Certificates in Dart
import 'dart:io' show HttpClient;
Future<bool> isSecuredWithValidCert(String uriString) async {
final uri = Uri.parse(uriString);
final client = HttpClient();
try {
await client.headUrl(uri).then((r) => r.close());
return true;
} on HandshakeException {
return false;
}
}
void testIt() async {
await isSecuredWithValidCert('https://expired.badssl.com');
await isSecuredWithValidCert('https://wrong.host.badssl.com');
await isSecuredWithValidCert('https://self-signed.badssl.com');
await isSecuredWithValidCert('https://untrusted-root.badssl.com');
await isSecuredWithValidCert('https://revoked.badssl.com');
}
Displaying Popup Menus in Flutter
enum ImageAction { copy }
PopupMenuItem<ImageAction> copyButton({VoidCallback? onPressed}) =>
PopupMenuItem<ImageAction>(
value: ImageAction.copy,
child: TextButton.icon(
icon: Icon(Icons.copy),
label: Text('Copy'),
onPressed: onPressed,
),
);
class HomePage extends StatelessWidget {
const HomePage({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('Flutter'),
),
body: Center(
child: PopupMenuButton<ImageAction>(
elevation: 10,
offset: Offset(0, 50),
itemBuilder: (_) => [
copyButton(
onPressed: () {
print('Copy the image...');
},
),
],
child: Image.network('https://bit.ly/3ywI8l6'),
),
),
);
}
}
Implementing Drag and Drop in Flutter
class HomePage extends StatefulWidget {
HomePage({Key? key}) : super(key: key);
@override
_HomePageState createState() => _HomePageState();
}
class _HomePageState extends State<HomePage> {
String? _imageUrl;
bool shouldAccept(String? value) => Uri.tryParse(value ?? '') != null;
Widget dragTargetBuilder(
BuildContext context,
List<String?> incoming,
dynamic rejected,
) {
final emptyContainer = Container(
color: Colors.grey[200],
height: 200,
child: Center(
child: Text('Drag an image here'),
),
);
if (incoming.isNotEmpty) {
_imageUrl = incoming.first;
}
if (_imageUrl == null) {
return emptyContainer;
}
try {
final uri = Uri.parse(_imageUrl ?? '');
return Container(
color: Colors.grey[200],
height: 200,
child: Center(
child: Image.network(uri.toString()),
),
);
} on FormatException {
return emptyContainer;
}
}
static final firstImageUrl = 'https://bit.ly/3xnoJTm';
static final secondImageUrl = 'https://bit.ly/3hIuC78';
final firstImage = Image.network(firstImageUrl);
final secondImage = Image.network(secondImageUrl);
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(title: Text('Tooltips in Flutter')),
body: Padding(
padding: const EdgeInsets.all(8.0),
child: Column(
children: [
DragTarget<String>(
onWillAccept: shouldAccept,
builder: dragTargetBuilder,
),
SizedBox(height: 10.0),
DraggableImage(
imageWidget: firstImage,
imageUrl: firstImageUrl,
),
SizedBox(height: 10.0),
DraggableImage(
imageWidget: secondImage,
imageUrl: secondImageUrl,
),
],
),
),
);
}
}
class DraggableImage extends StatelessWidget {
const DraggableImage({
Key? key,
required this.imageWidget,
required this.imageUrl,
}) : super(key: key);
final Image imageWidget;
final String imageUrl;
@override
Widget build(BuildContext context) {
return Draggable<String>(
data: imageUrl,
feedback: Container(
width: MediaQuery.of(context).size.width,
decoration: BoxDecoration(
boxShadow: [
BoxShadow(
blurRadius: 30,
color: Colors.black,
spreadRadius: 10,
),
],
),
child: imageWidget,
),
child: imageWidget,
);
}
}
Dismissing List Items in Flutter
const gridImages = [
'https://bit.ly/3x7J5Qt',
'https://bit.ly/3dLJNeD',
'https://bit.ly/3ywI8l6',
'https://bit.ly/3jRSRCu',
'https://bit.ly/36fNNj9',
'https://bit.ly/3jOueGG',
'https://bit.ly/3qYOtDm',
'https://bit.ly/3wt11Ec',
'https://bit.ly/3yvFg7X',
'https://bit.ly/3ywzOla',
'https://bit.ly/3wnASpW',
'https://bit.ly/3jXSDto',
];
class HomePage extends StatelessWidget {
const HomePage({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
return Scaffold(
body: CustomScrollView(
slivers: [
CustomAppBar(),
CustomGridView(),
CustomListView(
imageUrls: gridImages,
),
],
),
);
}
}
class _CustomListViewState extends State<CustomListView> {
@override
Widget build(BuildContext context) {
return SliverPadding(
padding: EdgeInsets.all(8.0),
sliver: SliverList(
delegate: SliverChildBuilderDelegate(
(context, index) {
final url = widget.imageUrls[index];
return Dismissible(
key: ValueKey(url),
onDismissed: (_) {
widget.imageUrls.remove(url);
},
background: Container(
color: Colors.red,
child: FittedBox(
alignment: Alignment.centerRight,
fit: BoxFit.fitHeight,
child: Icon(Icons.delete, color: Colors.white),
),
),
child: Padding(
padding: const EdgeInsets.only(bottom: 8.0),
child: Image.network(url),
),
);
},
childCount: widget.imageUrls.length,
),
),
);
}
}
class CustomListView extends StatefulWidget {
final List<String> imageUrls;
const CustomListView({
Key? key,
required this.imageUrls,
}) : super(key: key);
@override
_CustomListViewState createState() => _CustomListViewState();
}
class CustomGridView extends StatelessWidget {
const CustomGridView({
Key? key,
}) : super(key: key);
@override
Widget build(BuildContext context) {
return SliverPadding(
padding: EdgeInsets.all(8.0),
sliver: SliverGrid(
gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(
crossAxisCount: 3,
mainAxisSpacing: 10,
crossAxisSpacing: 10,
childAspectRatio: 1.0,
),
delegate: SliverChildBuilderDelegate(
(context, index) {
return Container(
width: 100,
height: 100,
child: Image.network(gridImages[index]),
);
},
childCount: gridImages.length,
),
),
);
}
}
class CustomAppBar extends StatelessWidget {
const CustomAppBar({
Key? key,
}) : super(key: key);
@override
Widget build(BuildContext context) {
return SliverAppBar(
backgroundColor: Colors.orange[300],
forceElevated: true,
pinned: false,
snap: false,
floating: true,
expandedHeight: 172,
flexibleSpace: FlexibleSpaceBar(
title: Text(
'Flutter',
style: TextStyle(
fontSize: 30,
color: Colors.white,
decoration: TextDecoration.underline,
),
),
collapseMode: CollapseMode.parallax,
background: Image.network('https://bit.ly/3x7J5Qt'),
),
);
}
}
Animating Widgets with Ease in Flutter
class Ball extends StatefulWidget {
const Ball({Key? key}) : super(key: key);
@override
_BallState createState() => _BallState();
}
class _BallState extends State<Ball> with SingleTickerProviderStateMixin {
late final AnimationController _controller;
late final Animation _animation;
@override
void initState() {
super.initState();
_controller = AnimationController(
vsync: this,
duration: Duration(seconds: 4),
reverseDuration: Duration(seconds: 4),
);
_animation = Tween(begin: 0.0, end: 2 * pi).animate(_controller);
}
@override
void dispose() {
_controller.dispose();
super.dispose();
}
@override
Widget build(BuildContext context) {
_controller.repeat();
return AnimatedBuilder(
animation: _animation,
builder: (context, image) {
return Transform.rotate(
angle: _animation.value,
child: image,
);
},
child: Image.network('https://bit.ly/3xspdrp'),
);
}
}
class HomePage extends StatelessWidget {
const HomePage({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('Animated Builder in Flutter'),
),
body: Center(
child: Ball(),
),
);
}
}
Displaying Tool Tips in Flutter
const imagesAndInfo = [
['https://bit.ly/3xnoJTm', 'Stockholm, Sweden'],
['https://bit.ly/3hIuC78', 'Dalarna, Sweden'],
['https://bit.ly/3wi9mdG', 'Brighton, UK'],
['https://bit.ly/3dSSMuy', 'Hove, UK'],
['https://bit.ly/3xoWCmV', 'Kerala, India'],
['https://bit.ly/3hGmjZC', 'Salvador da Bahia, Brazil']
];
class HomePage extends StatelessWidget {
const HomePage({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(title: Text('Tooltips in Flutter')),
body: ListView.builder(
itemCount: imagesAndInfo.length,
itemBuilder: (_, index) {
return Padding(
padding: const EdgeInsets.only(top: 8.0, left: 8.0, right: 8.0),
child: Tooltip(
decoration: BoxDecoration(
color: Colors.black,
boxShadow: [
BoxShadow(
color: Colors.white.withAlpha(180),
offset: Offset.zero,
spreadRadius: 30.0,
blurRadius: 30.0,
),
],
borderRadius: BorderRadius.all(Radius.circular(8.0)),
),
textStyle: TextStyle(fontSize: 20, color: Colors.white),
message: imagesAndInfo[index][1],
child: Image.network(
imagesAndInfo[index][0],
),
),
);
},
),
);
}
}
Displaying Assorted Widgets Inside TableView in Flutter
const natureUrls = [
'https://bit.ly/3dAtFwy',
'https://bit.ly/36cHehe',
'https://bit.ly/365uqt1',
'https://bit.ly/3x7J5Qt',
'https://bit.ly/3jBvJYU',
'https://bit.ly/3yhbHHi'
];
extension ToImage on String {
Widget toPaddedNetworkImage() => Padding(
padding: const EdgeInsets.all(8.0),
child: Image.network(this),
);
}
extension ToImages on List<String> {
List<Widget> toPaddedNetworkImages() =>
map((str) => str.toPaddedNetworkImage()).toList();
}
extension ToTableRow on List<Widget> {
TableRow toTableRow() => TableRow(children: this);
}
class ListPaginator<T> extends Iterable {
final List<List<T>> list;
ListPaginator({required List<T> input, required int itemsPerPage})
: list = [
for (var i = 0; i < input.length; i += itemsPerPage)
input.getRange(i, min(input.length, i + itemsPerPage)).toList(),
];
@override
Iterator get iterator => list.iterator;
}
class HomePage extends StatelessWidget {
final provider = ListPaginator<String>(
input: natureUrls,
itemsPerPage: 3,
);
HomePage({Key? key}) : super(key: key);
Iterable<TableRow> getRows() sync* {
for (final List<String> urlBatch in provider) {
final networkImages = urlBatch.toPaddedNetworkImages();
yield TableRow(children: networkImages);
}
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('TableView in Flutter'),
),
body: SingleChildScrollView(
child: Table(
defaultVerticalAlignment: TableCellVerticalAlignment.bottom,
children: getRows().toList(),
),
),
);
}
}
Page Indicator with Page View in Flutter
const dashes = [
'https://bit.ly/3gHlTCU',
'https://bit.ly/3wOLO1c',
'https://bit.ly/3cXWD9j',
'https://bit.ly/3gT5Qk2',
];
class PageText extends StatelessWidget {
final int current;
final int total;
const PageText({
Key? key,
required this.current,
required this.total,
}) : super(key: key);
@override
Widget build(BuildContext context) {
return Text(
'Page ${current + 1} of $total',
style: TextStyle(fontSize: 30.0, shadows: [
Shadow(
offset: Offset(0.0, 1.0),
blurRadius: 20.0,
color: Colors.black.withAlpha(140),
)
]),
);
}
}
class _HomePageState extends State<HomePage> {
var _index = 0;
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(title: Text('Page Indicator')),
body: SafeArea(
child: Column(
children: [
Expanded(
child: PageView.builder(
onPageChanged: (pageIndex) {
setState(() => _index = pageIndex);
},
scrollDirection: Axis.horizontal,
itemCount: dashes.length,
itemBuilder: (context, index) {
return Column(
mainAxisAlignment: MainAxisAlignment.center,
children: [
Image.network(dashes[index]),
Text('Dash #${index + 1}'),
],
);
},
),
),
PageText(current: _index, total: dashes.length)
],
),
),
);
}
}
Animating and Moving a Floating Action Button in Flutter
class HomePage extends StatefulWidget {
const HomePage({Key? key}) : super(key: key);
@override
_HomePageState createState() => _HomePageState();
}
const List<FloatingActionButtonLocation> locations = [
FloatingActionButtonLocation.centerDocked,
FloatingActionButtonLocation.startDocked,
FloatingActionButtonLocation.startFloat,
FloatingActionButtonLocation.centerFloat,
FloatingActionButtonLocation.endFloat,
FloatingActionButtonLocation.endDocked
];
extension GoAround<T> on List<T> {
T elementByGoingAround(int index) {
final finalIndex = index >= length ? index.remainder(length) : index;
return this[finalIndex];
}
}
class HomePage extends StatefulWidget {
const HomePage({Key? key}) : super(key: key);
@override
_HomePageState createState() => _HomePageState();
}
class _HomePageState extends State<HomePage> {
var _locationIndex = 0;
FloatingActionButtonLocation get location =>
locations.elementByGoingAround(_locationIndex);
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('Floating Action Button'),
),
floatingActionButtonLocation: location,
floatingActionButton: FloatingActionButton(
onPressed: () {
setState(() => _locationIndex += 1);
},
child: Icon(Icons.add),
),
bottomNavigationBar: BottomNavigationBar(
backgroundColor: Colors.yellow[600],
selectedItemColor: Colors.black,
items: [
BottomNavigationBarItem(
icon: Icon(Icons.bedtime),
label: 'Item 1',
),
BottomNavigationBarItem(
icon: Icon(Icons.access_alarms),
label: 'Item 2',
)
],
currentIndex: 0,
),
);
}
}
Fading Network Image Widget in Flutter
class FadingNetworkImage extends StatefulWidget {
final String url;
const FadingNetworkImage({Key? key, required this.url}) : super(key: key);
@override
_FadingNetworkImageState createState() => _FadingNetworkImageState();
}
class _FadingNetworkImageState extends State<FadingNetworkImage>
with SingleTickerProviderStateMixin {
late final AnimationController _controller;
late final Animation<double> _animation;
@override
void initState() {
super.initState();
_controller =
AnimationController(vsync: this, duration: Duration(seconds: 1));
_animation = Tween(begin: 0.0, end: 1.0).animate(_controller);
}
@override
void dispose() {
_controller.dispose();
super.dispose();
}
@override
Widget build(BuildContext context) {
return Image.network(
widget.url,
frameBuilder: (context, child, frame, wasSynchronouslyLoaded) {
_controller.reset();
_controller.forward();
return FadeTransition(opacity: _animation, child: child);
},
loadingBuilder: (context, child, loadingProgress) {
final totalBytes = loadingProgress?.expectedTotalBytes;
final bytesLoaded = loadingProgress?.cumulativeBytesLoaded;
if (totalBytes != null && bytesLoaded != null) {
return LinearProgressIndicator(
value: bytesLoaded / totalBytes,
);
} else {
return child;
}
},
errorBuilder: (context, error, stackTrace) {
return Text('Error!');
},
);
}
}
const dashes = [
'https://bit.ly/3gHlTCU',
'https://bit.ly/3wOLO1c',
'https://bit.ly/3cXWD9j',
'https://bit.ly/3gT5Qk2',
];
extension GoAround<T> on List<T> {
T elementByGoingAround(int index) {
final finalIndex = index >= length ? index.remainder(length) : index;
return this[finalIndex];
}
}
class HomePage extends StatefulWidget {
const HomePage({Key? key}) : super(key: key);
@override
_HomePageState createState() => _HomePageState();
}
class _HomePageState extends State<HomePage> {
int _index = 0;
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('Faded Image'),
),
body: Center(
child: Column(
children: [
FadingNetworkImage(
url: dashes.elementByGoingAround(_index),
),
TextButton(
onPressed: () {
setState(() => _index += 1);
},
child: Text('Load next Dash'),
),
],
)),
);
}
}
Transparent Alert Dialogs in Flutter
TextStyle get whiteTextStyle => TextStyle(color: Colors.white);
Future<void> showTextDialog({
required BuildContext context,
required String text,
}) {
return showDialog(
context: context,
builder: (context) {
return AlertDialog(
shape: RoundedRectangleBorder(
borderRadius: BorderRadius.all(
Radius.circular(10),
),
side: BorderSide(
color: Colors.white,
style: BorderStyle.solid,
width: 2,
),
),
backgroundColor: Colors.black.withAlpha(150),
titleTextStyle: whiteTextStyle,
contentTextStyle: whiteTextStyle,
content: Text(text),
actions: [
TextButton(
style: TextButton.styleFrom(primary: Colors.white),
onPressed: () {
Navigator.of(context).pop();
},
child: Text('OK'),
)
],
);
},
);
}
class HomePage extends StatelessWidget {
const HomePage({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(
'Rounded Corder Dialog',
),
),
body: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: [
Image.network('https://bit.ly/3ywI8l6'),
TextButton(
onPressed: () async {
await showTextDialog(
context: context,
text: 'Hello world',
);
},
child: Text('Show dialog'),
),
],
),
);
}
}
Network Image Size in Dart
import 'dart:ui' as ui;
Future<Size> getImageSize(String uri) {
final image = Image.network('https://bit.ly/3dAtFwy');
final comp = Completer<ui.Image>();
image.image
.resolve(
ImageConfiguration.empty,
)
.addListener(
ImageStreamListener(
(ImageInfo info, _) => comp.complete(info.image),
),
);
return comp.future.then(
(image) => Size(
image.width.toDouble(),
image.height.toDouble(),
),
);
}
void testIt() async {
final imageSize = await getImageSize('https://bit.ly/3dAtFwy');
print(imageSize);
assert(imageSize.width == 2048.0);
assert(imageSize.height == 1365.0);
print(imageSize.aspectRatio);
}
Animated Icons in Flutter
class _HomePageState extends State<HomePage>
with SingleTickerProviderStateMixin {
late final Animation<double> _animation;
late final AnimationController _controller;
@override
void initState() {
super.initState();
_controller = AnimationController(
vsync: this,
duration: Duration(seconds: 1),
);
_animation = Tween(
begin: 0.0,
end: 1.0,
).animate(_controller);
}
@override
void dispose() {
_controller.dispose();
super.dispose();
}
@override
Widget build(BuildContext context) {
_controller.repeat(reverse: true);
return Scaffold(
appBar: AppBar(
title: Text('Animated Icons in Fluter'),
),
body: Center(
child: AnimatedIcon(
color: Colors.green[300],
size: MediaQuery.of(context).size.width,
icon: AnimatedIcons.search_ellipsis,
progress: _animation,
),
),
);
}
}
class HomePage extends StatefulWidget {
const HomePage({Key? key}) : super(key: key);
@override
_HomePageState createState() => _HomePageState();
}
Custom Scroll Views in Flutter
const gridImages = [
'https://bit.ly/3x7J5Qt',
'https://bit.ly/3dLJNeD',
'https://bit.ly/3ywI8l6',
'https://bit.ly/3jRSRCu',
'https://bit.ly/36fNNj9',
'https://bit.ly/3jOueGG',
'https://bit.ly/3qYOtDm',
'https://bit.ly/3wt11Ec',
'https://bit.ly/3yvFg7X',
'https://bit.ly/3ywzOla',
'https://bit.ly/3wnASpW',
'https://bit.ly/3jXSDto',
];
class HomePage extends StatelessWidget {
const HomePage({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
return Scaffold(
body: CustomScrollView(
slivers: [
CustomAppBar(),
CustomGridView(),
CustomListView(),
],
),
);
}
}
class CustomListView extends StatelessWidget {
const CustomListView({
Key? key,
}) : super(key: key);
@override
Widget build(BuildContext context) {
return SliverPadding(
padding: EdgeInsets.all(8.0),
sliver: SliverList(
delegate: SliverChildBuilderDelegate(
(context, index) {
return Padding(
padding: const EdgeInsets.only(bottom: 8.0),
child: Image.network(gridImages[index]),
);
},
childCount: gridImages.length,
),
),
);
}
}
class CustomGridView extends StatelessWidget {
const CustomGridView({
Key? key,
}) : super(key: key);
@override
Widget build(BuildContext context) {
return SliverPadding(
padding: EdgeInsets.all(8.0),
sliver: SliverGrid(
gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(
crossAxisCount: 3,
mainAxisSpacing: 10,
crossAxisSpacing: 10,
childAspectRatio: 1.0,
),
delegate: SliverChildBuilderDelegate(
(context, index) {
return Container(
width: 100,
height: 100,
child: Image.network(gridImages[index]),
);
},
childCount: gridImages.length,
),
),
);
}
}
class CustomAppBar extends StatelessWidget {
const CustomAppBar({
Key? key,
}) : super(key: key);
@override
Widget build(BuildContext context) {
return SliverAppBar(
backgroundColor: Colors.orange[300],
forceElevated: true,
pinned: false,
snap: false,
floating: true,
expandedHeight: 172,
flexibleSpace: FlexibleSpaceBar(
title: Text(
'Flutter',
style: TextStyle(
fontSize: 30,
color: Colors.white,
decoration: TextDecoration.underline,
),
),
collapseMode: CollapseMode.parallax,
background: Image.network('https://bit.ly/3x7J5Qt'),
),
);
}
}
Parallax App Bar in Flutter
JSON HTTP Requests in Dart
URL Timeouts in Dart
Detecting URL File Types in Dart
Paginated Lists in Dart
Requesting DELETE on APIs in Dart
Animated Containers in Flutter
Hiding Widgets in Flutter
Simple Opacity Animation in Flutter
Vignette Widget in Flutter
Drop Down Button Configuration and Usage in Flutter
Expandable List Items in Flutter
Infinite Scrolling in Flutter
Infinite Arrays in Dart
Custom Color Picker Component in Flutter
Displaying and Reacting to Switches in Flutter
Displaying Bottom Bars in Flutter
Displaying Buttons on AppBar in Flutter
Displaying Bottom Sheets in Flutter
Converting Enums to Radio Buttons in Flutter
Check Existence of Websites in Flutter
Images inside AlertDialog in Flutter
Returning Values from AlertDialog in Flutter
Simple Grid View in Flutter
Rendering Bullet Points in Flutter
Retrying Futures in Flutter
Containers as ClipOvals in Flutter
Rich Texts in Flutter
Wrapping Widgets in Flutter
Sweep Gradients in Flutter
Stream and StreamBuilder in Flutter
Blur Effect in Flutter
Convert Enums to Strings in Dart
Replacing Text in TextField in Flutter
Aspect Ratio in Flutter
Zoom and Pan in Flutter
Resizing Images in Flutter to Fit Screen Height
Validating URLs in Flutter
FrameBuilder for Network Images in Flutter
Adding Shadow to Icons in Flutter
Calculating Median of Lists in Dart
Generic Functions with Reduce in Dart
Passing Back Data From a Screen to the Previous One in Flutter
Flinging an Animation in Flutter
Fade Animations in Flutter
Throttling User Input in Flutter
Censoring TextFields in Flutter
Customizing TextButton in Flutter
Multiline TextFields in Flutter
Filtering TextField Input in Flutter
Focusing Manually on TextFields in Flutter
Data Streams Over HTTP/HTTPs in Dart
Catching Nonexistent Accessors or Methods in Dart
Using Expando in Dart
Implementing Custom Maps in Dart
Dynamically Calling Functions in Dart
Factory Constructors in Dart
Calculating the Sum of List Items in Dart
Removing Duplicate Strings in Lists in Dart (Case-Insensitive)
Implementing Range in Dart
Converting Lists to Maps in Dart
Implementing Hashable in Dart
Random Name Generator in Dart
Capturing Stack Traces in Dart Exceptions
Removing Duplicates from Lists in Dart
Optional Spread Operator in Dart
Calling Optional Functions in Dart
Odd-Even Sort in Dart
Implementing Zip and Tuples in Dart
Swapping Values in Lists with XOR in Dart
Waiting for Multiple Futures in Dart
Using Queues as Stacks in Dart
Custom Iterators in Dart
Iterables as Ranges and Transform in Dart
Errors vs Exceptions in Dart
Custom Annotations in Dart
Classes as Enums in Dart
Spread Operator in Collection Literals in Dart
StreamBuilder and StreamController in Dart
Almost Equal in Dart
Enum Associated Values in Dart
Implementing Comparable in Dart
Implementing Custom Integer Types in Dart
Custom Subscripts in Dart
Dart List Enumeration with Index
Applying Mixins to Other Mixins in Dart
Parameter Types in Dart
Custom Exceptions in Dart
rethrowing Exceptions in Dart
mixins and JSON Parsing in Dart
mixins vs abstract classes in Dart
Drawing Shapes in Flutter with LayoutBuilder, CustomPaint and CustomPainter
Generic Type Aliases in Dart
Callable Classes in Dart
Synchronous Generators in Dart
Implicit Interfaces in Dart
Did you know that in #Dart, every #class implicitly exports an #interface that can be #implemented (as opposed to #extended) by other classes? This is called "implicit interface".
Do you know how "const" constructors work in #Dart?
Did you know that in #Dart, it is actually preferred to use #async and #await over using raw #Futures?
In #Dart, you can use a combination of #Initializer #List plus default values for your class #member #fields to create elegant and handy convenience initializers
Did you know that in #Dart, you can extract elements of a certain type from your Lists using the #whereType #generic #function instead of calculating the #equality yourselves?
Do you know about #Type #Promotion in Dart?
"address" is an optional field of the "Person" class. If you look at the "doThis()" function you see that I'm saving the value of address in a local variable and then comparing it with null and then returning if it's null. The Dart compiler is intelligent enough to understand that after the if-statement, "address" is NOT null anymore since you've already compared it with null and returned from the function.
If you look at the "insteadOfThis" function, the first one, the Dart compiler cannot make the same assumption if you don't first store the value of address in a local variable. In that first function the Dart compiler, even after the if-statement, needs you to refer to address as an optional, using "address?" syntax.
The mechanism the Dart compiler uses in the "doThis()" function is called Type Promotion.
4 lines of #Dart code that include the #spread operator, #cascade #operator, #generics, #extensions, #private prefix and #getters
Functions as First Class Citizens in Dart
Download Details:
Author: vandadnp
Source Code: https://github.com/vandadnp/flutter-tips-and-tricks
#flutter #dart #programming #developer
1631534473
Openapi Generator for Dart/Flutter
This library is the dart/flutter implementation of openapi client sdk code generation.
With this library, you can generate openapi client sdk libraries from your openapi specification right in your flutter/dart projects. (see example)
To be used together with openapi-generator
Usage
Include openapi-generator-annotations as a dependency in the dependencies section of your pubspec.yaml file :
dependencies:
openapi_generator_annotations: ^2.2.0
Add openapi-generator in the dev dependencies section of your pubspec.yaml file:
dev_dependencies:
openapi_generator: ^2.2.0
Annotate a dart class with @Openapi() annotation
@Openapi(
additionalProperties:
AdditionalProperties(pubName: 'petstore_api', pubAuthor: 'Johnny depp'),
inputSpecFile: 'example/openapi-spec.yaml',
generatorName: Genrator.dart,
outputDirectory: 'api/petstore_api')
class Example extends OpenapiGeneratorConfig {}
Run command below to generate open api client sdk from spec file specified in annotation.
flutter pub run build_runner build --delete-conflicting-outputs
The api sdk will be generated in the folder specified in the annotation. See examples for more details
To use the generated api in your project, import it into your pubspec
Give a thumbs up if you like this library
Known Issues
Dependency issues/conflicts
This is not an issue with this library but with flutter/dart in general. If you are having issues with dependencies, what you can do is make use of dependency overrides. This is added to the pubspec.yaml of the generated package and then the pubspec must be added to the .openapi-generator-ignore of the generated package. For example, let's assume you want to override the analyzer package for the generated source
in generatedsource/pubspec.yaml add the following
dependency_overrides:
analyzer: 1.0.0
Then in generatedsources/.openapi-generator-ignore, add the below so that the pubspec is not overwritten next time you run source gen
pubspec.yaml
The above steps are usefull when you have issues with dependency conflicts, clashes. You can even use it to upgrade the library packages in the generated source.
Features and bugs
Please file feature requests and bugs at the issue tracker.
Use this package as a library
Depend on it
Run this command:
With Dart:
$ dart pub add openapi_generator_annotationsWith Flutter:
$ flutter pub add openapi_generator_annotationsThis will add a line like this to your package's pubspec.yaml (and run an implicit dart pub get):
dependencies:
openapi_generator_annotations: ^3.2.1Alternatively, your editor might support dart pub get or flutter pub get. Check the docs for your editor to learn more.
Import it
Now in your Dart code, you can use:
import 'package:openapi_generator_annotations/openapi_generator_annotations.dart'; import 'package:openapi_generator_annotations/openapi_generator_annotations.dart';
@Openapi(
additionalProperties:
AdditionalProperties(pubName: 'petstore_api', pubAuthor: 'Johnny dep'),
inputSpecFile: 'example/openapi-spec.yaml',
generatorName: Generator.dio,
outputDirectory: 'api/petstore_api')
class Example extends OpenapiGeneratorConfig {} Download Details:
Author: gibahjoe
Source Code: https://github.com/gibahjoe/openapi-generator-dart
1591340335
How To Take Help Of Referencing Generator
APA Referencing Generator
Many students use APA style as the key citation style in their assignment in university or college. Although, many people find it quite difficult to write the reference of the source. You ought to miss the names and dates of authors. Hence, APA referencing generator is important for reducing the burden of students. They can now feel quite easy to do the assignments on time.
The functioning of APA referencing generator
If you are struggling hard to write the APA referencing then you can take the help of APA referencing generator. It will create an excellent list. You are required to enter the information about the source. Just ensure that the text is credible and original. If you will copy references then it is a copyright violation.
You can use a referencing generator in just a click. It will generate the right references for all the sources. You are required to organize in alphabetical order. The generator will make sure that you will get good grades.
How to use APA referencing generator?
Select what is required to be cited such as journal, book, film, and others. You can choose the type of required citations list and enter all the required fields. The fields are dates, author name, title, editor name, and editions, name of publishers, chapter number, page numbers, and title of journals. You can click for reference to be generated and you will get the desired result.
Chicago Referencing Generator
Do you require the citation style? You can rely on Chicago Referencing Generator and will ensure that you will get the right citation in just a click. The generator is created to provide solutions to students to cite their research paper in Chicago style. It has proved to be the quickest and best citation generator on the market. The generator helps to sort the homework issues in few seconds. It also saves a lot of time and energy.
This tool helps researchers, professional writers, and students to manage and generate text citation essays. It will help to write Chicago style in a fast and easy way. It also provides details and directions for formatting and cites resources.
So, you must stop wasting the time and can go for Chicago Referencing Generator or APA referencing generator. These citation generators will help to solve the problem of citation issues. You can easily create citations by using endnotes and footnotes.
So, you can generate bibliographies, references, in-text citations, and title pages. These are fully automatic referencing style. You are just required to enter certain details about the citation and you will get the citation in the proper and required format.
So, if you are feeling any problem in doing assignment then you can take the help of assignment help.
If you require help for Assignment then livewebtutors is the right place for you. If you see our prices, you will observe that they are actually very affordable. Also, you can always expect a discount. Our team is capable and versatile enough to offer you exactly what you need, the best services for the prices you can afford.
read more:- Are you struggling to write a bibliography? Use Harvard referencing generator
#apa referencing generator #harvard referencing generator #chicago referencing generator #mla referencing generator #deakin referencing generator #oxford referencing generator
1658977500
A Ruby Library for Generating Text with Recursive Template Grammars
Calyx
Calyx provides a simple API for generating text with declarative recursive grammars.
Install
Command Line
gem install calyx
Gemfile
gem 'calyx'
Examples
The best way to get started quickly is to install the gem and run the examples locally.
Any Gradient
Requires Roda and Rack to be available.
gem install roda
Demonstrates how to use Calyx to construct SVG graphics. Any Gradient generates a rectangle with a linear gradient of random colours.
Run as a web server and preview the output in a browser (http://localhost:9292):
ruby examples/any_gradient.rb
Or generate SVG files via a command line pipe:
ruby examples/any_gradient > gradient1.xml
Tiny Woodland Bot
Requires the Twitter client gem and API access configured for a specific Twitter handle.
gem install twitter
Demonstrates how to use Calyx to make a minimal Twitter bot that periodically posts unique tweets. See @tiny_woodland on Twitter and the writeup here.
TWITTER_CONSUMER_KEY=XXX-XXX
TWITTER_CONSUMER_SECRET=XXX-XXX
TWITTER_ACCESS_TOKEN=XXX-XXX
TWITTER_CONSUMER_SECRET=XXX-XXX
ruby examples/tiny_woodland_bot.rb
Faker
Faker is a popular library for generating fake names and associated sample data like internet addresses, company names and locations.
This example demonstrates how to use Calyx to reproduce the same functionality using custom lists defined in a YAML configuration file.
ruby examples/faker.rb
Usage
Require the library and inherit from Calyx::Grammar to construct a set of rules to generate a text.
require 'calyx'
class HelloWorld < Calyx::Grammar
start 'Hello world.'
end
To generate the text itself, initialize the object and call the generate method.
hello = HelloWorld.new
hello.generate
# > "Hello world."
Obviously, this hardcoded sentence isn’t very interesting by itself. Possible variations can be added to the text by adding additional rules which provide a named set of text strings. The rule delimiter syntax ({}) can be used to substitute the generated content of other rules.
class HelloWorld < Calyx::Grammar
start '{greeting} world.'
greeting 'Hello', 'Hi', 'Hey', 'Yo'
end
Each time #generate runs, it evaluates the tree and randomly selects variations of rules to construct a resulting string.
hello = HelloWorld.new
hello.generate
# > "Hi world."
hello.generate
# > "Hello world."
hello.generate
# > "Yo world."
By convention, the start rule specifies the default starting point for generating the final text. You can start from any other named rule by passing it explicitly to the generate method.
class HelloWorld < Calyx::Grammar
hello 'Hello world.'
end
hello = HelloWorld.new
hello.generate(:hello)
Block Constructors
As an alternative to subclassing, you can also construct rules unique to an instance by passing a block when initializing the class:
hello = Calyx::Grammar.new do
start '{greeting} world.'
greeting 'Hello', 'Hi', 'Hey', 'Yo'
end
hello.generate
Template Expressions
Basic rule substitution uses single curly brackets as delimiters for template expressions:
fruit = Calyx::Grammar.new do
start '{colour} {fruit}'
colour 'red', 'green', 'yellow'
fruit 'apple', 'pear', 'tomato'
end
6.times { fruit.generate }
# => "yellow pear"
# => "red apple"
# => "green tomato"
# => "red pear"
# => "yellow tomato"
# => "green apple"
Nesting and Substitution
Rules are recursive. They can be arbitrarily nested and connected to generate larger and more complex texts.
class HelloWorld < Calyx::Grammar
start '{greeting} {world_phrase}.'
greeting 'Hello', 'Hi', 'Hey', 'Yo'
world_phrase '{happy_adj} world', '{sad_adj} world', 'world'
happy_adj 'wonderful', 'amazing', 'bright', 'beautiful'
sad_adj 'cruel', 'miserable'
end
Nesting and hierarchy can be manipulated to balance consistency with novelty. The exact same word atoms can be combined in a variety of ways to produce strikingly different resulting texts.
module HelloWorld
class Sentiment < Calyx::Grammar
start '{happy_phrase}', '{sad_phrase}'
happy_phrase '{happy_greeting} {happy_adj} world.'
happy_greeting 'Hello', 'Hi', 'Hey', 'Yo'
happy_adj 'wonderful', 'amazing', 'bright', 'beautiful'
sad_phrase '{sad_greeting} {sad_adj} world.'
sad_greeting 'Goodbye', 'So long', 'Farewell'
sad_adj 'cruel', 'miserable'
end
class Mixed < Calyx::Grammar
start '{greeting} {adj} world.'
greeting 'Hello', 'Hi', 'Hey', 'Yo', 'Goodbye', 'So long', 'Farewell'
adj 'wonderful', 'amazing', 'bright', 'beautiful', 'cruel', 'miserable'
end
end
Random Sampling
By default, the outcomes of generated rules are selected with Ruby’s built-in pseudorandom number generator (as seen in methods like Kernel.rand and Array.sample). To seed the random number generator, pass in an integer seed value as the first argument to the constructor:
grammar = Calyx::Grammar.new(seed: 12345) do
# rules...
end
Alternatively, you can pass a preconfigured instance of Ruby’s stdlib Random class:
random = Random.new(12345)
grammar = Calyx::Grammar.new(rng: random) do
# rules...
end
When a random seed isn’t supplied, Time.new.to_i is used as the default seed, which makes each run of the generator relatively unique.
Weighted Choices
Choices can be weighted so that some rules have a greater probability of expanding than others.
Weights are defined by passing a hash instead of a list of rules where the keys are strings or symbols representing the grammar rules and the values are weights.
Weights can be represented as floats, integers or ranges.
- Floats must be in the interval 0..1 and the given weights for a production must sum to 1.
- Ranges must be contiguous and cover the entire interval from 1 to the maximum value of the largest range.
- Integers (Fixnums) will produce a distribution based on the sum of all given numbers, with each number being a fraction of that sum.
The following definitions produce an equivalent weighting of choices:
Calyx::Grammar.new do
start 'heads' => 1, 'tails' => 1
end
Calyx::Grammar.new do
start 'heads' => 0.5, 'tails' => 0.5
end
Calyx::Grammar.new do
start 'heads' => 1..5, 'tails' => 6..10
end
Calyx::Grammar.new do
start 'heads' => 50, 'tails' => 50
end
There’s a lot of interesting things you can do with this. For example, you can model the triangular distribution produced by rolling 2d6:
Calyx::Grammar.new do
start(
'2' => 1,
'3' => 2,
'4' => 3,
'5' => 4,
'6' => 5,
'7' => 6,
'8' => 5,
'9' => 4,
'10' => 3,
'11' => 2,
'12' => 1
)
end
Or reproduce Gary Gygax’s famous generation table from the original Dungeon Master’s Guide (page 171):
Calyx::Grammar.new do
start(
:empty => 0.6,
:monster => 0.1,
:monster_treasure => 0.15,
:special => 0.05,
:trick_trap => 0.05,
:treasure => 0.05
)
empty 'Empty'
monster 'Monster Only'
monster_treasure 'Monster and Treasure'
special 'Special'
trick_trap 'Trick/Trap.'
treasure 'Treasure'
end
String Modifiers
Dot-notation is supported in template expressions, allowing you to call any available method on the String object returned from a rule. Formatting methods can be chained arbitrarily and will execute in the same way as they would in native Ruby code.
greeting = Calyx::Grammar.new do
start '{hello.capitalize} there.', 'Why, {hello} there.'
hello 'hello', 'hi'
end
4.times { greeting.generate }
# => "Hello there."
# => "Hi there."
# => "Why, hello there."
# => "Why, hi there."
You can also extend the grammar with custom modifiers that provide useful formatting functions.
Filters
Filters accept an input string and return the transformed output:
greeting = Calyx::Grammar.new do
filter :shoutycaps do |input|
input.upcase
end
start '{hello.shoutycaps} there.', 'Why, {hello.shoutycaps} there.'
hello 'hello', 'hi'
end
4.times { greeting.generate }
# => "HELLO there."
# => "HI there."
# => "Why, HELLO there."
# => "Why, HI there."
Mappings
The mapping shortcut allows you to specify a map of regex patterns pointing to their resulting substitution strings:
green_bottle = Calyx::Grammar.new do
mapping :pluralize, /(.+)/ => '\\1s'
start 'One green {bottle}.', 'Two green {bottle.pluralize}.'
bottle 'bottle'
end
2.times { green_bottle.generate }
# => "One green bottle."
# => "Two green bottles."
Modifier Mixins
In order to use more intricate rewriting and formatting methods in a modifier chain, you can add methods to a module and embed it in a grammar using the modifier classmethod.
Modifier methods accept a single argument representing the input string from the previous step in the expression chain and must return a string, representing the modified output.
module FullStop
def full_stop(input)
input << '.'
end
end
hello = Calyx::Grammar.new do
modifier FullStop
start '{hello.capitalize.full_stop}'
hello 'hello'
end
hello.generate
# => "Hello."
To share custom modifiers across multiple grammars, you can include the module in Calyx::Modifiers. This will make the methods available to all subsequent instances:
module FullStop
def full_stop(input)
input << '.'
end
end
class Calyx::Modifiers
include FullStop
end
Monkeypatching String
Alternatively, you can combine methods from existing Gems that monkeypatch String:
require 'indefinite_article'
module FullStop
def full_stop
self << '.'
end
end
class String
include FullStop
end
noun_articles = Calyx::Grammar.new do
start '{fruit.with_indefinite_article.capitalize.full_stop}'
fruit 'apple', 'orange', 'banana', 'pear'
end
4.times { noun_articles.generate }
# => "An apple."
# => "An orange."
# => "A banana."
# => "A pear."
Memoized Rules
Rule expansions can be ‘memoized’ so that multiple references to the same rule return the same value. This is useful for picking a noun from a list and reusing it in multiple places within a text.
The @ sigil is used to mark memoized rules. This evaluates the rule and stores it in memory the first time it’s referenced. All subsequent references to the memoized rule use the same stored value.
# Without memoization
grammar = Calyx::Grammar.new do
start '{name} <{name.downcase}>'
name 'Daenerys', 'Tyrion', 'Jon'
end
3.times { grammar.generate }
# => Daenerys <jon>
# => Tyrion <daenerys>
# => Jon <tyrion>
# With memoization
grammar = Calyx::Grammar.new do
start '{@name} <{@name.downcase}>'
name 'Daenerys', 'Tyrion', 'Jon'
end
3.times { grammar.generate }
# => Tyrion <tyrion>
# => Daenerys <daenerys>
# => Jon <jon>
Note that the memoization symbol can only be used on the right hand side of a production rule.
Unique Rules
Rule expansions can be marked as ‘unique’, meaning that multiple references to the same rule always return a different value. This is useful for situations where the same result appearing twice would appear awkward and messy.
Unique rules are marked by the $ sigil.
grammar = Calyx::Grammar.new do
start "{$medal}, {$medal}, {$medal}"
medal 'Gold', 'Silver', 'Bronze'
end
grammar.generate
# => Silver, Bronze, Gold
Dynamically Constructing Rules
Template expansions can be dynamically constructed at runtime by passing a context map of rules to the #generate method:
class AppGreeting < Calyx::Grammar
start 'Hi {username}!', 'Welcome back {username}...', 'Hola {username}'
end
context = {
username: UserModel.username
}
greeting = AppGreeting.new
greeting.generate(context)
External File Formats
In addition to defining grammars in pure Ruby, you can load them from external JSON and YAML files:
hello = Calyx::Grammar.load('hello.yml')
hello.generate
The format requires a flat map with keys representing the left-hand side named symbols and the values representing the right hand side substitution rules.
In JSON:
{
"start": "{greeting} world.",
"greeting": ["Hello", "Hi", "Hey", "Yo"]
}
In YAML:
---
start: "{greeting} world."
greeting:
- Hello
- Hi
- Hey
- Yo
Accessing the Raw Generated Tree
Calling #evaluate on the grammar instance will give you access to the raw generated tree structure before it gets flattened into a string.
The tree is encoded as an array of nested arrays, with the leading symbols labeling the choices and rules selected, and the trailing terminal leaves encoding string values.
This may not make a lot of sense unless you’re familiar with the concept of s-expressions. It’s a fairly speculative feature at this stage, but it leads to some interesting possibilities.
grammar = Calyx::Grammar.new do
start 'Riddle me ree.'
end
grammar.evaluate
# => [:start, [:choice, [:concat, [[:atom, "Riddle me ree."]]]]]
Roadmap
Rough plan for stabilising the API and features for a 1.0 release.
| Version | Features planned |
|---|---|
0.6 | |
0.7 | |
0.8 | |
0.9 | |
0.10 | |
0.11 | |
0.12 | |
0.13 | |
0.14 | |
0.15 | |
0.16 | |
0.17 | |
Credits
Author & Maintainer
Contributors
Author: Maetl
Source Code: https://github.com/maetl/calyx
License: MIT license
1620992479
How To Create User-Generated Content? [A Simple Guide To Grow Your Brand]
In this digital world, online businesses aspire to catch the attention of users in a modern and smarter way. To achieve it, they need to traverse through new approaches. Here comes to spotlight is the user-generated content or UGC.
What is user-generated content?
“ It is the content by users for users.”
Generally, the UGC is the unbiased content created and published by the brand users, social media followers, fans, and influencers that highlight their experiences with the products or services. User-generated content has superseded other marketing trends and fallen into the advertising feeds of brands. Today, more than 86 percent of companies use user-generated content as part of their marketing strategy.
In this article, we have explained the ten best ideas to create wonderful user-generated content for your brand. Let’s start without any further ado.
- Content From Social Media Platforms
In the year 2020, there are 3.81 million people actively using social media around the globe. That is the reason social media content matters. Whenever users look at the content on social media that is posted by an individual, then they may be influenced by their content. Perhaps, it can be used to gain more customers or followers on your social media platforms.
Generally, social media platforms help the brand to generate content for your users. Any user content that promotes your brand on the social media platform is the user-generated content for your business. When users create and share content on social media, they get 28% higher engagement than a standard company post.
Furthermore, you can embed your social media feed on your website also. you can use the Social Stream Designer WordPress plugin that will integrate various social media feeds from different social media platforms like Facebook, Twitter, Instagram, and many more. With this plugin, you can create a responsive wall on your WordPress website or blog in a few minutes. In addition to this, the plugin also provides more than 40 customization options to make your social stream feeds more attractive.
- Consumer Survey
The customer survey provides powerful insights you need to make a better decision for your business. Moreover, it is great user-generated content that is useful for identifying unhappy consumers and those who like your product or service.
In general, surveys can be used to figure out attitudes, reactions, to evaluate customer satisfaction, estimate their opinions about different problems. Another benefit of customer surveys is that collecting outcomes can be quick. Within a few minutes, you can design and load a customer feedback survey and send it to your customers for their response. From the customer survey data, you can find your strengths, weaknesses, and get the right way to improve them to gain more customers.
- Run Contests
A contest is a wonderful way to increase awareness about a product or service. Contest not just helps you to enhance the volume of user-generated content submissions, but they also help increase their quality. However, when you create a contest, it is important to keep things as simple as possible.
Additionally, it is the best way to convert your brand leads to valuable customers. The key to running a successful contest is to make sure that the reward is fair enough to motivate your participation. If the product is relevant to your participant, then chances are they were looking for it in the first place, and giving it to them for free just made you move forward ahead of your competitors. They will most likely purchase more if your product or service satisfies them.
Furthermore, running contests also improve the customer-brand relationship and allows more people to participate in it. It will drive a real result for your online business. If your WordPress website has Google Analytics, then track contest page visits, referral traffic, other website traffic, and many more.
- Review And Testimonials
Customer reviews are a popular user-generated content strategy. One research found that around 68% of customers must see at least four reviews before trusting a brand. And, approximately 40 percent of consumers will stop using a business after they read negative reviews.
The business reviews help your consumers to make a buying decision without any hurdle. While you may decide to remove all the negative reviews about your business, those are still valuable user-generated content that provides honest opinions from real users. Customer feedback can help you with what needs to be improved with your products or services. This thing is not only beneficial to the next customer but your business as a whole.
Reviews are powerful as the platform they are built upon. That is the reason it is important to gather reviews from third-party review websites like Google review, Facebook review, and many more, or direct reviews on a website. It is the most vital form of feedback that can help brands grow globally and motivate audience interactions.
However, you can also invite your customers to share their unique or successful testimonials. It is a great way to display your products while inspiring others to purchase from your website.
- Video Content
A great video is a video that is enjoyed by visitors. These different types of videos, such as 360-degree product videos, product demo videos, animated videos, and corporate videos. The Facebook study has demonstrated that users spend 3x more time watching live videos than normal videos. With the live video, you can get more user-created content.
Moreover, Instagram videos create around 3x more comments rather than Instagram photo posts. Instagram videos generally include short videos posted by real customers on Instagram with the tag of a particular brand. Brands can repost the stories as user-generated content to engage more audiences and create valid promotions on social media.
Similarly, imagine you are browsing a YouTube channel, and you look at a brand being supported by some authentic customers through a small video. So, it will catch your attention. With the videos, they can tell you about the branded products, especially the unboxing videos displaying all the inside products and how well it works for them. That type of video is enough to create a sense of desire in the consumers.
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