Learning Flutter Widgets, Widget 4 – Animated Container

Flutter AnimatedContainer class

Animated version of Container that gradually changes its values over a period of time.

The AnimatedContainer will automatically animate between the old and new values of properties when they change using the provided curve and duration. Properties that are null are not animated. Its child and descendants are not animated.

This class is useful for generating simple implicit transitions between different parameters to Container with its internal AnimationController. For more complex animations, you’ll likely want to use a subclass of AnimatedWidget such as the DecoratedBoxTransition or use your own AnimationController.

Example Source Code

// Flutter code sample for AnimatedContainer

// The following example (depicted above) transitions an AnimatedContainer
// between two states. It adjusts the [height], [width], [color], and
// [alignment] properties when tapped.

import 'package:flutter/material.dart';

void main() => runApp(MyApp());

/// This Widget is the main application widget.
class MyApp extends StatelessWidget {
  static const String _title = 'Flutter Code Sample';

  Widget build(BuildContext context) {
    return MaterialApp(
      title: _title,
      home: Scaffold(
        appBar: AppBar(title: const Text(_title)),
        body: MyStatefulWidget(),

class MyStatefulWidget extends StatefulWidget {
  MyStatefulWidget({Key key}) : super(key: key);

  _MyStatefulWidgetState createState() => _MyStatefulWidgetState();

class _MyStatefulWidgetState extends State<MyStatefulWidget> {
  bool selected = false;

  Widget build(BuildContext context) {
    return GestureDetector(
      onTap: () {
        setState(() {
          selected = !selected;
      child: Center(
        child: AnimatedContainer(
          width: selected ? 200.0 : 100.0,
          height: selected ? 100.0 : 200.0,
          color: selected ? Colors.red : Colors.blue,
              selected ? Alignment.center : AlignmentDirectional.topCenter,
          duration: Duration(seconds: 2),
          curve: Curves.fastOutSlowIn,
          child: FlutterLogo(size: 75),

See also:


        Key key, 
        AlignmentGeometry alignment, 
        EdgeInsetsGeometry padding, 
        Color color, 
        Decoration decoration, 
        Decoration foregroundDecoration, 
        double width, 
        double height, 
        BoxConstraints constraints, 
        EdgeInsetsGeometry margin, 
        Matrix4 transform, 
        Widget child, 
        Curve curve: Curves.linear, 
        @required Duration duration, 
        VoidCallback onEnd
Creates a container that animates its parameters implicitly. [...]


alignment → AlignmentGeometry
Align the child within the container. [...]

child → Widget
The child contained by the container. [...]

constraints → BoxConstraints
Additional constraints to apply to the child. [...]

curve → Curve
The curve to apply when animating the parameters of this container.
final, inherited

decoration → Decoration
The decoration to paint behind the child[...]

duration → Duration
The duration over which to animate the parameters of this container.
final, inherited

foregroundDecoration → Decoration
The decoration to paint in front of the child.

hashCode → int
The hash code for this object. [...]
@nonVirtual, read-only, inherited

key → Key
Controls how one widget replaces another widget in the tree. [...]
final, inherited

margin → EdgeInsetsGeometry
Empty space to surround the decoration and child.

onEnd → VoidCallback
Called every time an animation completes. [...]
final, inherited

padding → EdgeInsetsGeometry
Empty space to inscribe inside the decoration. The child, if any, is placed inside this padding.

runtimeType → Type
A representation of the runtime type of the object.
read-only, inherited

transform → Matrix4
The transformation matrix to apply before painting the container.


createElement() → StatefulElement
Creates a StatefulElement to manage this widget's location in the tree. [...]

createState() → _AnimatedContainerState
Creates the mutable state for this widget at a given location in the tree. [...]

debugDescribeChildren() → List<DiagnosticsNode>
Returns a list of DiagnosticsNode objects describing this node's children. [...]
@protected, inherited

debugFillProperties(DiagnosticPropertiesBuilder properties) → void
Add additional properties associated with the node. [...]

noSuchMethod(Invocation invocation) → dynamic
Invoked when a non-existent method or property is accessed. [...]

toDiagnosticsNode({String name, DiagnosticsTreeStyle style}) → DiagnosticsNode
Returns a debug representation of the object that is used by debugging tools and by DiagnosticsNode.toStringDeep[...]

toString({DiagnosticLevel minLevel: DiagnosticLevel.info}) → String
Returns a string representation of this object.

toStringDeep({String prefixLineOne: '', String prefixOtherLines, DiagnosticLevel minLevel: DiagnosticLevel.debug}) → String
Returns a string representation of this node and its descendants. [...]

toStringShallow({String joiner: ', ', DiagnosticLevel minLevel: DiagnosticLevel.debug}) → String
Returns a one-line detailed description of the object. [...]

toStringShort() → String
A short, textual description of this widget.


operator ==(Object other) → bool
The equality operator. [...]
@nonVirtual, inherited

Source Website: api.flutter.dev


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