Hudson  Kunde

Hudson Kunde

1602816846

Flutter: Taking Pictures with the Bloc Pattern

Working with flutter makes it really easy to build applications using the camera. Just by following the small example of the camera_plugin we can successfully take pictures with minimum lines of code.

However when the moment comes to cover the camera with tests, things get harder. In this article we are going to see how we can use Bloc Design Pattern to take photos, making our app more robust and easily testable.

For the purpose of this article, I created a simple app named MyPhotos (available on GitHub) using Bloc to take some pictures and show them on the home page:

Image for post

MyPhotos Demo

The app contains two blocs:

  • PhotosBloc, in charge of loading, adding and deleting the photos.
  • CameraBloc, in charge of the interactions with the CameraController.

We are going to focus on the CameraBloc as it is the purpose of this article.

Bloc Construction

CameraBloc events:

We only need 3 events to manage the camera.

  • CameraInitialized to start the camera (ask for permission and stream the camera).
  • CameraStopped to release the resources used by the camera.
  • CameraCaptured to take a picture.

CameraBloc states:

Depending on the events the bloc can emit 6 states:

  • CameraInitial for the initial state.
  • CameraReady when the camera is ready to take a picture.
  • CameraFailure when the camera failed to initialize.
  • CameraCaptureInProgress when the camera is taking a picture.
  • CameraCaptureSuccess when the camera successfully took a picture.
  • CameraCaptureFailure when an error happened during the capture.

CameraBloc logic:

To be able to mock the camera’s controller during the tests, we need to pass it through dependency injection. We could directly pass an instance of CameraController through the constructor, but I prefer to use a class with a method in charge to instantiate the controller to be able to catch any error inside of the bloc.

class CameraUtils {
  Future<CameraController> getCameraController(
      ResolutionPreset resolutionPreset,
      CameraLensDirection cameraLensDirection) async {
    final cameras = await availableCameras();
    final camera = cameras
        .firstWhere((camera) => camera.lensDirection == cameraLensDirection);

    return CameraController(camera, resolutionPreset, enableAudio: false);
  }

  Future<String> getPath() async => join(
        (await getTemporaryDirectory()).path,
        '${DateTime.now()}.png',
      );
}

By passing an object of CameraUtils we will then be able to mock all of its methods. In a more complex example we could add methods to compress, crop…

class CameraBloc extends Bloc<CameraEvent, CameraState> {
  final CameraUtils cameraUtils;
  final ResolutionPreset resolutionPreset;
  final CameraLensDirection cameraLensDirection;

  CameraController _controller;

  CameraBloc({
    @required this.cameraUtils,
    this.resolutionPreset = ResolutionPreset.high,
    this.cameraLensDirection = CameraLensDirection.back,
  }) : super(CameraInitial());
  // ...
}

When the user opens the camera’s screen, the event CameraInitialized is sent. The camera’s controller is created and initialized.

  Stream<CameraState> _mapCameraInitializedToState(CameraInitialized event) async* {
    try {
      _controller = await cameraUtils
          .getCameraController(resolutionPreset, cameraLensDirection);
      await _controller.initialize();
      yield CameraReady();
    } on CameraException catch (error) {
      _controller?.dispose();
      yield CameraFailure(error: error.description);
    } catch (error) {
      yield CameraFailure(error: error.toString());
    }
  }

If an error occurred when selecting a camera (or if there is no camera) the second catch will handle the exception and emits CameraFailure .

By calling _controller.initialize() the plugin automatically checks if the permissions are granted and if not, opens a pop-up to ask for the permissions.

  • If the user denies the permission, the method throws a CameraException and the bloc emits CameraFailure.
  • If the user accepts, the bloc emits CameraReady.

#flutter #mobile-apps #programming #developer #web-development

What is GEEK

Buddha Community

Flutter: Taking Pictures with the Bloc Pattern

Google's Flutter 1.20 stable announced with new features - Navoki

Flutter Google cross-platform UI framework has released a new version 1.20 stable.

Flutter is Google’s UI framework to make apps for Android, iOS, Web, Windows, Mac, Linux, and Fuchsia OS. Since the last 2 years, the flutter Framework has already achieved popularity among mobile developers to develop Android and iOS apps. In the last few releases, Flutter also added the support of making web applications and desktop applications.

Last month they introduced the support of the Linux desktop app that can be distributed through Canonical Snap Store(Snapcraft), this enables the developers to publish there Linux desktop app for their users and publish on Snap Store.  If you want to learn how to Publish Flutter Desktop app in Snap Store that here is the tutorial.

Flutter 1.20 Framework is built on Google’s made Dart programming language that is a cross-platform language providing native performance, new UI widgets, and other more features for the developer usage.

Here are the few key points of this release:

Performance improvements for Flutter and Dart

In this release, they have got multiple performance improvements in the Dart language itself. A new improvement is to reduce the app size in the release versions of the app. Another performance improvement is to reduce junk in the display of app animation by using the warm-up phase.

sksl_warm-up

If your app is junk information during the first run then the Skia Shading Language shader provides for pre-compilation as part of your app’s build. This can speed it up by more than 2x.

Added a better support of mouse cursors for web and desktop flutter app,. Now many widgets will show cursor on top of them or you can specify the type of supported cursor you want.

Autofill for mobile text fields

Autofill was already supported in native applications now its been added to the Flutter SDK. Now prefilled information stored by your OS can be used for autofill in the application. This feature will be available soon on the flutter web.

flutter_autofill

A new widget for interaction

InteractiveViewer is a new widget design for common interactions in your app like pan, zoom drag and drop for resizing the widget. Informations on this you can check more on this API documentation where you can try this widget on the DartPad. In this release, drag-drop has more features added like you can know precisely where the drop happened and get the position.

Updated Material Slider, RangeSlider, TimePicker, and DatePicker

In this new release, there are many pre-existing widgets that were updated to match the latest material guidelines, these updates include better interaction with Slider and RangeSliderDatePicker with support for date range and time picker with the new style.

flutter_DatePicker

New pubspec.yaml format

Other than these widget updates there is some update within the project also like in pubspec.yaml file format. If you are a flutter plugin publisher then your old pubspec.yaml  is no longer supported to publish a plugin as the older format does not specify for which platform plugin you are making. All existing plugin will continue to work with flutter apps but you should make a plugin update as soon as possible.

Preview of embedded Dart DevTools in Visual Studio Code

Visual Studio code flutter extension got an update in this release. You get a preview of new features where you can analyze that Dev tools in your coding workspace. Enable this feature in your vs code by _dart.previewEmbeddedDevTools_setting. Dart DevTools menu you can choose your favorite page embed on your code workspace.

Network tracking

The updated the Dev tools comes with the network page that enables network profiling. You can track the timings and other information like status and content type of your** network calls** within your app. You can also monitor gRPC traffic.

Generate type-safe platform channels for platform interop

Pigeon is a command-line tool that will generate types of safe platform channels without adding additional dependencies. With this instead of manually matching method strings on platform channel and serializing arguments, you can invoke native class and pass nonprimitive data objects by directly calling the Dartmethod.

There is still a long list of updates in the new version of Flutter 1.2 that we cannot cover in this blog. You can get more details you can visit the official site to know more. Also, you can subscribe to the Navoki newsletter to get updates on these features and upcoming new updates and lessons. In upcoming new versions, we might see more new features and improvements.

You can get more free Flutter tutorials you can follow these courses:

#dart #developers #flutter #app developed #dart devtools in visual studio code #firebase local emulator suite in flutter #flutter autofill #flutter date picker #flutter desktop linux app build and publish on snapcraft store #flutter pigeon #flutter range slider #flutter slider #flutter time picker #flutter tutorial #flutter widget #google flutter #linux #navoki #pubspec format #setup flutter desktop on windows

Terry  Tremblay

Terry Tremblay

1598396940

What is Flutter and why you should learn it?

Flutter is an open-source UI toolkit for mobile developers, so they can use it to build native-looking** Android and iOS** applications from the same code base for both platforms. Flutter is also working to make Flutter apps for Web, PWA (progressive Web-App) and Desktop platform (Windows,macOS,Linux).

flutter-mobile-desktop-web-embedded_min

Flutter was officially released in December 2018. Since then, it has gone a much stronger flutter community.

There has been much increase in flutter developers, flutter packages, youtube tutorials, blogs, flutter examples apps, official and private events, and more. Flutter is now on top software repos based and trending on GitHub.

Flutter meaning?

What is Flutter? this question comes to many new developer’s mind.

humming_bird_dart_flutter

Flutter means flying wings quickly, and lightly but obviously, this doesn’t apply in our SDK.

So Flutter was one of the companies that were acquired by **Google **for around $40 million. That company was based on providing gesture detection and recognition from a standard webcam. But later when the Flutter was going to release in alpha version for developer it’s name was Sky, but since Google already owned Flutter name, so they rename it to Flutter.

Where Flutter is used?

Flutter is used in many startup companies nowadays, and even some MNCs are also adopting Flutter as a mobile development framework. Many top famous companies are using their apps in Flutter. Some of them here are

Dream11

Dream11

NuBank

NuBank

Reflectly app

Reflectly app

Abbey Road Studios

Abbey Road Studios

and many more other apps. Mobile development companies also adopted Flutter as a service for their clients. Even I was one of them who developed flutter apps as a freelancer and later as an IT company for mobile apps.

Flutter as a service

#dart #flutter #uncategorized #flutter framework #flutter jobs #flutter language #flutter meaning #flutter meaning in hindi #google flutter #how does flutter work #what is flutter

Flutter App

Flutter App

1641357547

How to Build out a Shopping Cart App using BLoC Pattern & Flutter

In this application, you learn how to build out a shopping cart application using the #flutter #bLoC #pattern with beautiful UI. Take a look. Happy Coding! 💗💗

source code: https://github.com/smrity24/shopping-cart-app-using-bloc-pattern 
Become A Patreon to get full Source code: https://www.patreon.com/learnflutterwithsmrity 

Subscribe: https://www.youtube.com/c/LearnFlutterWithSmrity/featured 

#flutter #bloc 

Búsqueda lineal en Python

En esta publicación de Python, aprenderá lo siguiente:

  • ¿Qué es una búsqueda lineal?
  • Algoritmo de búsqueda lineal
  • Escriba un programa Python para búsqueda lineal usando While Loop
  • Escriba un programa Python para búsqueda lineal usando For Loop
  • Búsqueda lineal en el programa Python usando recursividad

¿Qué es una búsqueda lineal?

En primer lugar, una búsqueda lineal, también conocida como búsqueda secuencial, este método se utiliza para encontrar un elemento dentro de una lista o matriz. Comprueba cada elemento de la lista uno por uno / secuencialmente hasta que se encuentra una coincidencia o se ha buscado en toda la lista.

Algoritmo de búsqueda lineal

Implemente la búsqueda lineal siguiendo los pasos a continuación:

  • Recorre la lista / matriz usando un bucle.
  • En cada iteración, asocie el  target valor con el valor dado de la lista / matriz.
    • Si los valores coinciden, devuelve el índice actual de la lista / matriz.
    • De lo contrario, continúe con el siguiente elemento de matriz / lista.
  • Si no se encuentra ninguna coincidencia, regrese  -1.

Escriba un programa Python para búsqueda lineal usando While Loop

# python program for linear search using while loop

#define list
lst = []

#take input list size
num = int(input("Enter size of list :- "))

for n in range(num):
    #append element in list/array
    numbers = int(input("Enter the array of %d element :- " %n))
    lst.append(numbers)

#take input number to be find in list   
x = int(input("Enter number to search in list :- "))

i = 0
flag = False

while i < len(lst):
	if lst[i] == x:
		flag = True
		break

	i = i + 1

if flag == 1:
	print('{} was found at index {}.'.format(x, i))
else:
	print('{} was not found.'.format(x))

Después de ejecutar el programa, la salida será:

Enter size of list :-  5
Enter the array of 0 element :-  10
Enter the array of 1 element :-  23
Enter the array of 2 element :-  56
Enter the array of 3 element :-  89
Enter the array of 4 element :-  200
Enter number to search in list :-  89
89 was found at index 3.

Escriba un programa Python para búsqueda lineal usando For Loop

# python program for linear search using for loop

#define list
lst = []

#take input list size
num = int(input("Enter size of list :- "))

for n in range(num):
    #append element in list/array
    numbers = int(input("Enter the array of %d element :- " %n))
    lst.append(numbers)

#take input number to be find in list   
x = int(input("Enter number to search in list :- "))

i = 0
flag = False

for i in range(len(lst)):
    if lst[i] == x:
        flag = True
        break

if flag == 1:
	print('{} was found at index {}.'.format(x, i))
else:
	print('{} was not found.'.format(x))

Después de ejecutar el programa, la salida será:

Enter size of list :-  6
Enter the array of 0 element :-  25
Enter the array of 1 element :-  50
Enter the array of 2 element :-  100
Enter the array of 3 element :-  200
Enter the array of 4 element :-  250
Enter the array of 5 element :-  650
Enter number to search in list :-  200
200 was found at index 3.

Búsqueda lineal en el programa Python usando recursividad

# python program for linear search using for loop

#define list
lst = []

#take input list size
num = int(input("Enter size of list :- "))

for n in range(num):
    #append element in list/array
    numbers = int(input("Enter the array of %d element :- " %n))
    lst.append(numbers)

#take input number to be find in list   
x = int(input("Enter number to search in list :- "))

# Recursive function to linear search x in arr[l..r]  
def recLinearSearch( arr, l, r, x): 
    if r < l: 
        return -1
    if arr[l] == x: 
        return l 
    if arr[r] == x: 
        return r 
    return recLinearSearch(arr, l+1, r-1, x) 

res = recLinearSearch(lst, 0, len(lst)-1, x) 

if res != -1:
	print('{} was found at index {}.'.format(x, res))
else:
	print('{} was not found.'.format(x))

Después de ejecutar el programa, la salida será:

Enter size of list :-  5
Enter the array of 0 element :-  14
Enter the array of 1 element :-  25
Enter the array of 2 element :-  63
Enter the array of 3 element :-  42
Enter the array of 4 element :-  78
Enter number to search in list :-  78
78 was found at index 4.

 

Pesquisa Linear em Python

Nesta postagem python, você aprenderá o seguinte:

  • O que é uma pesquisa linear?
  • Algoritmo de pesquisa linear
  • Escreva um programa Python para pesquisa linear usando loop while
  • Escreva um programa Python para pesquisa linear usando o loop for
  • Pesquisa linear no programa Python usando recursão

O que é uma pesquisa linear?

Em primeiro lugar, uma pesquisa linear, também conhecida como pesquisa sequencial, este método é usado para localizar um elemento dentro de uma lista ou array. Ele verifica cada elemento da lista um por um / sequencialmente até que uma correspondência seja encontrada ou toda a lista tenha sido pesquisada.

Algoritmo de pesquisa linear

Implemente a pesquisa linear seguindo as etapas abaixo:

  • Percorra a lista / array usando um loop.
  • Em cada iteração, associe o target valor ao  valor fornecido da lista / matriz.
    • Se os valores corresponderem, retorne o índice atual da lista / matriz.
    • Caso contrário, vá para o próximo elemento de array / lista.
  • Se nenhuma correspondência for encontrada, retorne  -1.

Escreva um programa Python para pesquisa linear usando loop while

# python program for linear search using while loop

#define list
lst = []

#take input list size
num = int(input("Enter size of list :- "))

for n in range(num):
    #append element in list/array
    numbers = int(input("Enter the array of %d element :- " %n))
    lst.append(numbers)

#take input number to be find in list   
x = int(input("Enter number to search in list :- "))

i = 0
flag = False

while i < len(lst):
	if lst[i] == x:
		flag = True
		break

	i = i + 1

if flag == 1:
	print('{} was found at index {}.'.format(x, i))
else:
	print('{} was not found.'.format(x))

Depois de executar o programa, a saída será:

Enter size of list :-  5
Enter the array of 0 element :-  10
Enter the array of 1 element :-  23
Enter the array of 2 element :-  56
Enter the array of 3 element :-  89
Enter the array of 4 element :-  200
Enter number to search in list :-  89
89 was found at index 3.

Escreva um programa Python para pesquisa linear usando o loop for

# python program for linear search using for loop

#define list
lst = []

#take input list size
num = int(input("Enter size of list :- "))

for n in range(num):
    #append element in list/array
    numbers = int(input("Enter the array of %d element :- " %n))
    lst.append(numbers)

#take input number to be find in list   
x = int(input("Enter number to search in list :- "))

i = 0
flag = False

for i in range(len(lst)):
    if lst[i] == x:
        flag = True
        break

if flag == 1:
	print('{} was found at index {}.'.format(x, i))
else:
	print('{} was not found.'.format(x))

Depois de executar o programa, a saída será:

Enter size of list :-  6
Enter the array of 0 element :-  25
Enter the array of 1 element :-  50
Enter the array of 2 element :-  100
Enter the array of 3 element :-  200
Enter the array of 4 element :-  250
Enter the array of 5 element :-  650
Enter number to search in list :-  200
200 was found at index 3.

Pesquisa linear no programa Python usando recursão

# python program for linear search using for loop

#define list
lst = []

#take input list size
num = int(input("Enter size of list :- "))

for n in range(num):
    #append element in list/array
    numbers = int(input("Enter the array of %d element :- " %n))
    lst.append(numbers)

#take input number to be find in list   
x = int(input("Enter number to search in list :- "))

# Recursive function to linear search x in arr[l..r]  
def recLinearSearch( arr, l, r, x): 
    if r < l: 
        return -1
    if arr[l] == x: 
        return l 
    if arr[r] == x: 
        return r 
    return recLinearSearch(arr, l+1, r-1, x) 

res = recLinearSearch(lst, 0, len(lst)-1, x) 

if res != -1:
	print('{} was found at index {}.'.format(x, res))
else:
	print('{} was not found.'.format(x))

Depois de executar o programa, a saída será:

Enter size of list :-  5
Enter the array of 0 element :-  14
Enter the array of 1 element :-  25
Enter the array of 2 element :-  63
Enter the array of 3 element :-  42
Enter the array of 4 element :-  78
Enter number to search in list :-  78
78 was found at index 4.