A widget that cross-fades between two given children and animates itself between their sizes.

The animation is controlled through the crossFadeState parameter. firstCurve and secondCurve represent the opacity curves of the two children. The firstCurve is inverted, i.e. it fades out when providing a growing curve like Curves.linear. The sizeCurve is the curve used to animate between the size of the fading-out child and the size of the fading-in child.

This widget is intended to be used to fade a pair of widgets with the same width. In the case where the two children have different heights, the animation crops overflowing children during the animation by aligning their top edge, which means that the bottom will be clipped.

The animation is automatically triggered when an existing AnimatedCrossFade is rebuilt with a different value for the crossFadeState property.

Sample code

This code fades between two representations of the Flutter logo. It depends on a boolean field _first; when _first is true, the first logo is shown, otherwise the second logo is shown. When the field changes state, the AnimatedCrossFade widget cross-fades between the two forms of the logo over three seconds.

new AnimatedCrossFade(
  duration: const Duration(seconds: 3),
  firstChild: const FlutterLogo(style: FlutterLogoStyle.horizontal, size: 100.0),
  secondChild: const FlutterLogo(style: FlutterLogoStyle.stacked, size: 100.0),
  crossFadeState: _first ? CrossFadeState.showFirst : CrossFadeState.showSecond,

See also:



AnimatedCrossFade({Key key, @required Widget firstChild, @required Widget secondChild, Curve firstCurve: Curves.linear, Curve secondCurve: Curves.linear, Curve sizeCurve: Curves.linear, AlignmentGeometry alignment: Alignment.topCenter, @required CrossFadeState crossFadeState, @required Duration duration, AnimatedCrossFadeBuilder layoutBuilder: defaultLayoutBuilder })
Creates a cross-fade animation widget. [...]


alignment AlignmentGeometry
How the children should be aligned while the size is animating. [...]
crossFadeState CrossFadeState
The child that will be shown when the animation has completed.
duration Duration
The duration of the whole orchestrated animation.
firstChild Widget
The child that is visible when crossFadeState is CrossFadeState.showFirst. It fades out when transitioning crossFadeState from CrossFadeState.showFirst to CrossFadeState.showSecond and vice versa.
firstCurve Curve
The fade curve of the first child. [...]
layoutBuilder AnimatedCrossFadeBuilder
A builder that positions the firstChild and secondChild widgets. [...]
secondChild Widget
The child that is visible when crossFadeState is CrossFadeState.showSecond. It fades in when transitioning crossFadeState from CrossFadeState.showFirst to CrossFadeState.showSecond and vice versa.
secondCurve Curve
The fade curve of the second child. [...]
sizeCurve Curve
The curve of the animation between the two children's sizes. [...]
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


createState() → _AnimatedCrossFadeState
Creates the mutable state for this widget at a given location in the tree. [...]
debugFillProperties(DiagnosticPropertiesBuilder description) → void
createElement() StatefulElement
Creates a StatefulElement to manage this widget's location in the tree. [...]
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. [...]
toDiagnosticsNode({String name, DiagnosticsTreeStyle style }) DiagnosticsNode
Returns a debug representation of the object that is used by debugging tools and by toStringDeep. [...]
toString({DiagnosticLevel minLevel: DiagnosticLevel.debug }) 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 ==(other) bool
The equality operator. [...]

Static Methods

defaultLayoutBuilder(Widget topChild, Key topChildKey, Widget bottomChild, Key bottomChildKey) Widget
The default layout algorithm used by AnimatedCrossFade. [...]