AnimatedOpacity class

Animated version of Opacity which automatically transitions the child's opacity over a given duration whenever the given opacity changes.

Animating an opacity is relatively expensive because it requires painting the child into an intermediate buffer.

Here's an illustration of what using this widget looks like, using a curve of Curves.fastOutSlowIn.

class LogoFade extends StatefulWidget {
  @override
  createState() => LogoFadeState();
}

class LogoFadeState extends State<LogoFade> {
  double opacityLevel = 1.0;

  void _changeOpacity() {
    setState(() => opacityLevel = opacityLevel == 0 ? 1.0 : 0.0);
  }

  @override
  Widget build(BuildContext context) {
    return Column(
      mainAxisAlignment: MainAxisAlignment.center,
      children: [
        AnimatedOpacity(
          opacity: opacityLevel,
          duration: Duration(seconds: 3),
          child: FlutterLogo(),
        ),
        RaisedButton(
          child: Text('Fade Logo'),
          onPressed: _changeOpacity,
        ),
      ],
    );
  }
}

See also:

  • FadeTransition, an explicitly animated version of this widget, where an Animation is provided by the caller instead of being built in.
Inheritance

Constructors

AnimatedOpacity({Key key, Widget child, @required double opacity, Curve curve: Curves.linear, @required Duration duration })
Creates a widget that animates its opacity implicitly. [...]
const

Properties

child → Widget
The widget below this widget in the tree. [...]
final
opacity → double
The target opacity. [...]
final
curve → Curve
The curve to apply when animating the parameters of this container.
final, inherited
duration → Duration
The duration over which to animate the parameters of this container.
final, inherited
hashCode → int
The hash code for this object. [...]
read-only, inherited
key → Key
Controls how one widget replaces another widget in the tree. [...]
final, inherited
runtimeType → Type
A representation of the runtime type of the object.
read-only, inherited

Methods

createState() → _AnimatedOpacityState
Creates the mutable state for this widget at a given location in the tree. [...]
override
debugFillProperties(DiagnosticPropertiesBuilder properties) → void
Add additional properties associated with the node. [...]
override
createElement() → StatefulElement
Creates a StatefulElement to manage this widget's location in the tree. [...]
inherited
debugDescribeChildren() → List<DiagnosticsNode>
Returns a list of DiagnosticsNode objects describing this node's children. [...]
@protected, inherited
noSuchMethod(Invocation invocation) → dynamic
Invoked when a non-existent method or property is accessed. [...]
inherited
toDiagnosticsNode({String name, DiagnosticsTreeStyle style }) → DiagnosticsNode
Returns a debug representation of the object that is used by debugging tools and by toStringDeep. [...]
inherited
toString({DiagnosticLevel minLevel: DiagnosticLevel.debug }) → String
Returns a string representation of this object.
inherited
toStringDeep({String prefixLineOne: '', String prefixOtherLines, DiagnosticLevel minLevel: DiagnosticLevel.debug }) → String
Returns a string representation of this node and its descendants. [...]
inherited
toStringShallow({String joiner: ', ', DiagnosticLevel minLevel: DiagnosticLevel.debug }) → String
Returns a one-line detailed description of the object. [...]
inherited
toStringShort() → String
A short, textual description of this widget.
inherited

Operators

operator ==(dynamic other) → bool
The equality operator. [...]
inherited