Still, it is work in progress — the catalogue of samples will grow. I will focus more on the usage of Flutter widgets rather than showcasing the components (Flutter Gallery is great for that!).
If you have an issue with “layouting” your Flutter or you wanna share your snippets with others, please drop a line!
Table of Contents
- Row and Column
- IntrinsicWidth and IntrinsicHeight
- Stack
- Expanded
- ConstrainedBox
- Container decoration: BoxDecoration
image: DecorationImage
border: Border
borderRadius: BorderRadius
shape: BoxShape
boxShadow: List<BoxShadow>
gradient: RadialGradient
backgroundBlendMode: BlendMode
- Material New!
shape: BeveledRectangleBorder
- SizedBox
- SafeArea
Row and Column
MainAxisAlignment
Row /*or Column*/( mainAxisAlignment: MainAxisAlignment.start, children: <Widget>[ Icon(Icons.star, size: 50), Icon(Icons.star, size: 50), Icon(Icons.star, size: 50), ], ),
Row /*or Column*/( mainAxisAlignment: MainAxisAlignment.center, children: <Widget>[ Icon(Icons.star, size: 50), Icon(Icons.star, size: 50), Icon(Icons.star, size: 50), ], ),
Row /*or Column*/( mainAxisAlignment: MainAxisAlignment.end, children: <Widget>[ Icon(Icons.star, size: 50), Icon(Icons.star, size: 50), Icon(Icons.star, size: 50), ], ),
Row /*or Column*/( mainAxisAlignment: MainAxisAlignment.spaceBetween, children: <Widget>[ Icon(Icons.star, size: 50), Icon(Icons.star, size: 50), Icon(Icons.star, size: 50), ], ),
Row /*or Column*/( mainAxisAlignment: MainAxisAlignment.spaceEvenly, children: <Widget>[ Icon(Icons.star, size: 50), Icon(Icons.star, size: 50), Icon(Icons.star, size: 50), ], ),
Row /*or Column*/( mainAxisAlignment: MainAxisAlignment.spaceAround, children: <Widget>[ Icon(Icons.star, size: 50), Icon(Icons.star, size: 50), Icon(Icons.star, size: 50), ], ),
You should use CrossAxisAlignment.baseline if you require for the baseline of different text be aligned.
Row(crossAxisAlignment: CrossAxisAlignment.baseline,
textBaseline: TextBaseline.alphabetic,
children: <Widget>[
Text(
‘Baseline’,
style: Theme.of(context).textTheme.display3,
),
Text(
‘Baseline’,
style: Theme.of(context).textTheme.body1,
),
],
),
CrossAxisAlignment
Row /or Column/(
crossAxisAlignment: CrossAxisAlignment.start,
children: <Widget>[
Icon(Icons.star, size: 50),
Icon(Icons.star, size: 200),
Icon(Icons.star, size: 50),
],
),
Row /or Column/(
crossAxisAlignment: CrossAxisAlignment.center,
children: <Widget>[
Icon(Icons.star, size: 50),
Icon(Icons.star, size: 200),
Icon(Icons.star, size: 50),
],
),
Row /or Column/(
crossAxisAlignment: CrossAxisAlignment.end,
children: <Widget>[
Icon(Icons.star, size: 50),
Icon(Icons.star, size: 200),
Icon(Icons.star, size: 50),
],
),
Row /or Column/(
crossAxisAlignment: CrossAxisAlignment.stretch,
children: <Widget>[
Icon(Icons.star, size: 50),
Icon(Icons.star, size: 200),
Icon(Icons.star, size: 50),
],
),
MainAxisSize
Row /or Column/(
mainAxisSize: MainAxisSize.max,
children: <Widget>[
Icon(Icons.star, size: 50),
Icon(Icons.star, size: 50),
Icon(Icons.star, size: 50),
],
),
Row /or Column/(
mainAxisSize: MainAxisSize.min,
children: <Widget>[
Icon(Icons.star, size: 50),
Icon(Icons.star, size: 50),
Icon(Icons.star, size: 50),
],
),
IntrinsicWidth and IntrinsicHeight
Want all the widgets inside Row or Column to be as tall/wide as the tallest/widest widget? Search no more!
In case you have this kind of layout:
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(title: Text(‘IntrinsicWidth’)),
body: Center(
child: Column(
children: <Widget>[
RaisedButton(
onPressed: () {},
child: Text(‘Short’),
),
RaisedButton(
onPressed: () {},
child: Text(‘A bit Longer’),
),
RaisedButton(
onPressed: () {},
child: Text(‘The Longest text button’),
),
],
),
),
);
}
But you would like to have all buttons as wide as the widest, just use IntrinsicWidth :
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(title: Text(‘IntrinsicWidth’)),
body: Center(
child: IntrinsicWidth(
child: Column(
crossAxisAlignment: CrossAxisAlignment.stretch,
children: <Widget>[
RaisedButton(
onPressed: () {},
child: Text(‘Short’),
),
RaisedButton(
onPressed: () {},
child: Text(‘A bit Longer’),
),
RaisedButton(
onPressed: () {},
child: Text(‘The Longest text button’),
),
],
),
),
),
);
}
In case you have a similar problem but you would like to have all the widgets as tall as the tallest just use combination of IntrinsicHeight and Row widgets.
Stack
Perfect for overlaying Widgets on top of each other
@override
Widget build(BuildContext context) {
Widget main = Scaffold(
appBar: AppBar(title: Text(‘Stack’)),
);return Stack(
fit: StackFit.expand,
children: <Widget>[
main,
Banner(
message: “Top Start”,
location: BannerLocation.topStart,
),
Banner(
message: “Top End”,
location: BannerLocation.topEnd,
),
Banner(
message: “Bottom Start”,
location: BannerLocation.bottomStart,
),
Banner(
message: “Bottom End”,
location: BannerLocation.bottomEnd,
),
],
);
}
With your own Widgets, you need to place them in Positioned Widget
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(title: Text(‘Stack’)),
body: Stack(
fit: StackFit.expand,
children: <Widget>[
Material(color: Colors.yellowAccent),
Positioned(
top: 0,
left: 0,
child: Icon(Icons.star, size: 50),
),
Positioned(
top: 340,
left: 250,
child: Icon(Icons.call, size: 50),
),
],
),
);
}
If you don’t want to guess the top/bottom values you can use LayoutBuilder to retrieve them
Widget build(BuildContext context) {
const iconSize = 50;
return Scaffold(
appBar: AppBar(title: Text(‘Stack with LayoutBuilder’)),
body: LayoutBuilder(
builder: (context, constraints) =>
Stack(
fit: StackFit.expand,
children: <Widget>[
Material(color: Colors.yellowAccent),
Positioned(
top: 0,
child: Icon(Icons.star, size: iconSize),
),
Positioned(
top: constraints.maxHeight - iconSize,
left: constraints.maxWidth - iconSize,
child: Icon(Icons.call, size: iconSize),
),
],
),
),
);
}
Expanded
Expanded works with Flex\Flexbox layout and is great for distributing space between multiple items.
Row(
children: <Widget>[
Expanded(
child: Container(
decoration: const BoxDecoration(color: Colors.red),
),
flex: 3,
),
Expanded(
child: Container(
decoration: const BoxDecoration(color: Colors.green),
),
flex: 2,
),
Expanded(
child: Container(
decoration: const BoxDecoration(color: Colors.blue),
),
flex: 1,
),
],
),
ConstrainedBox
By default, most of the widgets will use as little space as possible:
Card(child: const Text(‘Hello World!’), color: Colors.yellow)
ConstrainedBox allows a widget to use the remaining space as desired.
ConstrainedBox(
constraints: BoxConstraints.expand(),
child: const Card(
child: const Text(‘Hello World!’),
color: Colors.yellow,
),
),
Using BoxConstraints you specify how much space a widget can have — you specify min/max of height/width
BoxConstraints.expand uses infinite (all the available) amount of space unless specified:
ConstrainedBox(
constraints: BoxConstraints.expand(height: 300),
child: const Card(
child: const Text(‘Hello World!’),
color: Colors.yellow,
),
),
And it’s the same as:
ConstrainedBox(constraints: BoxConstraints(
minWidth: double.infinity,
maxWidth: double.infinity,
minHeight: 300,
maxHeight: 300,
),
child: const Card(
child: const Text(‘Hello World!’),
color: Colors.yellow,
),
),
Container
One of the most used Widgets — and for good reasons:
Container as a layout tool
When you don’t specify the height and the width of the Container, it will match its child’s size
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(title: Text(‘Container as a layout’)),
body: Container(
color: Colors.yellowAccent,
child: Text(“Hi”),
),
);
}
If you want to stretch the Container to match its parent, use double.infinity for the height and width properties
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(title: Text(‘Container as a layout’)),
body: Container(
height: double.infinity,
width: double.infinity,
color: Colors.yellowAccent,
child: Text(“Hi”),
),
);
}
Container as decoration
You can use color property to affect Container’s background but decoration and foregroundDecoration. (With those two properties, you can completely change how Container looks like but I will be talking about different decorations later as it quite big topic)
decoration is always placed behind the child, whereas foregroundDecoration is on top of the child
decoration
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(title: Text(‘Container.decoration’)),
body: Container(
height: double.infinity,
width: double.infinity,
decoration: BoxDecoration(color: Colors.yellowAccent),
child: Text(“Hi”),
),
);
}
decoration and foregroundDecoration
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(title: Text(‘Container.foregroundDecoration’)),
body: Container(
height: double.infinity,
width: double.infinity,
decoration: BoxDecoration(color: Colors.yellowAccent),
foregroundDecoration: BoxDecoration(color: Colors.red.withOpacity(0.5)),
child: Text(“Hi”),
),
);
}
Container as Transform
If you don’t want to use Transform widget to change your layout, you can use transform property straight from the Container
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(title: Text(‘Container.transform’)),
body: Container(
height: 300,
width: 300,
transform: Matrix4.rotationZ(pi / 4),
decoration: BoxDecoration(color: Colors.yellowAccent),
child: Text(
“Hi”,
textAlign: TextAlign.center,
),
),
);
}
BoxDecoration
Decoration is usually used on a Container widget to change how the container looks.
image: DecorationImage
Puts an image as a background:
Scaffold(
appBar: AppBar(title: Text(‘image: DecorationImage’)),
body: Center(
child: Container(
height: 200,
width: 200,
decoration: BoxDecoration(
color: Colors.yellow,
image: DecorationImage(
fit: BoxFit.fitWidth,
image: NetworkImage(
‘https://flutter.io/images/catalog-widget-placeholder.png’,
),
),
),
),
),
);
border: Border
Specifies how should the border of the Container look like.
Scaffold(
appBar: AppBar(title: Text(‘border: Border’)),
body: Center(
child: Container(
height: 200,
width: 200,
decoration: BoxDecoration(
color: Colors.yellow,
border: Border.all(color: Colors.black, width: 3),
),
),
),
);
borderRadius: BorderRadius
Enables border corners to be rounded.
borderRadius does not work if the shape of the decoration is BoxShape.circle
Scaffold(
appBar: AppBar(title: Text(‘borderRadius: BorderRadius’)),
body: Center(
child: Container(
height: 200,
width: 200,
decoration: BoxDecoration(
color: Colors.yellow,
border: Border.all(color: Colors.black, width: 3),
borderRadius: BorderRadius.all(Radius.circular(18)),
),
),
),
);
shape: BoxShape
Box decoration can be either a rectangle/square or an ellipse/circle.
For any other shape, you can use ShapeDecoration instead of BoxDecoration
Scaffold(
appBar: AppBar(title: Text(‘shape: BoxShape’)),
body: Center(
child: Container(
height: 200,
width: 200,
decoration: BoxDecoration(
color: Colors.yellow,
shape: BoxShape.circle,
),
),
),
);
boxShadow: List<BoxShadow>
Adds shadow to the Container.
This parameter is a list because you can specify multiple different shadows and merge them together.
Scaffold(
appBar: AppBar(title: Text(‘boxShadow: List<BoxShadow>’)),
body: Center(
child: Container(
height: 200,
width: 200,
decoration: BoxDecoration(
color: Colors.yellow,
boxShadow: const [
BoxShadow(blurRadius: 10),
],
),
),
),
);
gradient
There are three types of gradients: LinearGradient, RadialGradient and SweepGradient.
LinearGradient
Scaffold(appBar: AppBar(title: Text(‘gradient: LinearGradient’)),
body: Center(
child: Container(
height: 200,
width: 200,
decoration: BoxDecoration(
gradient: LinearGradient(
colors: const [
Colors.red,
Colors.blue,
],
),
),
),
),
);
RadialGradient
Scaffold(appBar: AppBar(title: Text(‘gradient: RadialGradient’)),
body: Center(
child: Container(
height: 200,
width: 200,
decoration: BoxDecoration(
gradient: RadialGradient(
colors: const [Colors.yellow, Colors.blue],
stops: const [0.4, 1.0],
),
),
),
),
);
SweepGradient
Scaffold(appBar: AppBar(title: Text(‘gradient: SweepGradient’)),
body: Center(
child: Container(
height: 200,
width: 200,
decoration: BoxDecoration(
gradient: SweepGradient(
colors: const [
Colors.blue,
Colors.green,
Colors.yellow,
Colors.red,
Colors.blue,
],
stops: const [0.0, 0.25, 0.5, 0.75, 1.0],
),
),
),
),
);
backgroundBlendMode
backgroundBlendMode is the most complex property of BoxDecoration.
It’s responsible for mixing together colors/gradients of BoxDecoration and whatever BoxDecoration is on top of.
With backgroundBlendMode you can use a long list of algorithms specified in BlendMode enum.
First, let’s set BoxDecoration as foregroundDecoration which is drawn on top of Container’s child (whereas decoration is drawn behind the child).
Scaffold(
appBar: AppBar(title: Text(‘backgroundBlendMode’)),
body: Center(
child: Container(
height: 200,
width: 200,
foregroundDecoration: BoxDecoration(
backgroundBlendMode: BlendMode.exclusion,
gradient: LinearGradient(
colors: const [
Colors.red,
Colors.blue,
],
),
),
child: Image.network(
‘https://flutter.io/images/catalog-widget-placeholder.png’,
),
),
),
);
backgroundBlendMode does not affect only the Container it’s localed in.
backgroundBlendMode changes the color of anything that is up the widget tree from the Container.
The following code has a parent Container that draws an image and child Container that uses backgroundBlendMode. Still, you would get the same effect as previously.
Scaffold(
appBar: AppBar(title: Text(‘backgroundBlendMode’)),
body: Center(
child: Container(
decoration: BoxDecoration(
image: DecorationImage(
image: NetworkImage(
‘https://flutter.io/images/catalog-widget-placeholder.png’,
),
),
),
child: Container(
height: 200,
width: 200,
foregroundDecoration: BoxDecoration(
backgroundBlendMode: BlendMode.exclusion,
gradient: LinearGradient(
colors: const [
Colors.red,
Colors.blue,
],
),
),
),
),
),
);
Material
Border with cut corners
Scaffold(
appBar: AppBar(title: Text(‘shape: BeveledRectangleBorder’)),
body: Center(
child: Material(
shape: const BeveledRectangleBorder(
borderRadius: BorderRadius.all(Radius.circular(20)),
side: BorderSide(color: Colors.black, width: 4),
),
color: Colors.yellow,
child: Container(
height: 200,
width: 200,
),
),
),
);
SizedBox
It’s one of the simplest but most useful Widgets
SizedBox as ConstrainedBox
SizedBox can work in a similar fashion as ConstrainedBox
SizedBox.expand(
child: Card(
child: Text(‘Hello World!’),
color: Colors.yellowAccent,
),
),
SizedBox as padding
When in need of adding padding or margin, you might choose Padding or Container widgets. But they can be more verbose and less redeable than adding a Sizedbox
Column(
children: <Widget>[
Icon(Icons.star, size: 50),
const SizedBox(height: 100),
Icon(Icons.star, size: 50),
Icon(Icons.star, size: 50),
],
),
SizedBox as an Invisible Object
Many time you would like to hide/show a widget depending on a bool
Widget build(BuildContext context) {
bool isVisible = …
return Scaffold(
appBar: AppBar(
title: Text(‘isVisible = $isVisible’),
),
body: isVisible
? Icon(Icons.star, size: 150)
: const SizedBox(),
);
}
Because SizedBox has a const constructor, using const SizedBox() is really cheap**.
** One cheaper solution would be to use Opacity widget and change the opacity value to 0.0 . The drawback of this solution is that the given widget would be only invisible, still would occupy the space.
SafeArea
On different Platforms, there are special areas like Status Bar on Android or the Notch on iPhone X that we might avoid drawing under.
The solution to this problem is SafeArea widget (example without/with SafeArea)
Widget build(BuildContext context) {
return Material(
color: Colors.blue,
child: SafeArea(
child: SizedBox.expand(
child: Card(color: Colors.yellowAccent),
),
),
);
}
Thanks for reading ❤
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Further reading
☞ Learn Flutter & Dart to Build iOS & Android Apps
☞ Flutter & Dart - The Complete Flutter App Development Course
☞ Dart and Flutter: The Complete Developer’s Guide
☞ Flutter Tutorial - Flight List UI Example In Flutter
☞ Flutter Tutorial for Beginners - Full Tutorial
☞ A Beginners Guide to the Flutter Bottom Sheet
☞ Flutter Course - Full Tutorial for Beginners (Build iOS and Android Apps)
☞ Flutter Tutorial For Beginners - Build Your First Flutter App
☞ Building the SwiftUI Sample App in Flutter
☞ Building Cryptocurrency Pricing App with Flutter
☞ Build a CRUD app using Firebase and Flutter (Provider)
☞ Build Firestore Todo App in flutter using “flutter_bloc”
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