PositionedTransition class

Animated version of Positioned which takes a specific Animation<RelativeRect> to transition the child's position from a start position to an end position over the lifetime of the animation.

Only works if it's the child of a Stack.

Here's an illustration of the PositionedTransition widget, with it's rect animated by a CurvedAnimation set to Curves.elasticInOut:

The following code implements the PositionedTransition as seen in the video above:

To create a local project with this code sample, run:
flutter create --sample=widgets.PositionedTransition.1 mysample

The following code implements the PositionedTransition as seen in the video above:

AnimationController _controller;

@override
void initState() {
  super.initState();
  _controller = AnimationController(
    duration: const Duration(seconds: 2),
    vsync: this,
  )..repeat(reverse: true);
}

@override
void dispose() {
  _controller.dispose();
  super.dispose();
}

@override
Widget build(BuildContext context) {
  final double smallLogo = 100;
  final double bigLogo = 200;

  return LayoutBuilder(
    builder: (context, constraints) {
      final Size biggest = constraints.biggest;
      return Stack(
        children: [
          PositionedTransition(
            rect: RelativeRectTween(
              begin: RelativeRect.fromSize(Rect.fromLTWH(0, 0, smallLogo, smallLogo), biggest),
              end: RelativeRect.fromSize(Rect.fromLTWH(biggest.width - bigLogo, biggest.height - bigLogo, bigLogo, bigLogo), biggest),
            ).animate(CurvedAnimation(
              parent: _controller,
              curve: Curves.elasticInOut,
            )),
            child: Padding(
              padding: const EdgeInsets.all(8),
              child: FlutterLogo()
            ),
          ),
        ],
      );
    },
  );
}

Constructors

PositionedTransition({Key key, @required Animation<RelativeRect> rect, @required Widget child}): Creates a transition for Positioned. [...]
const

Properties

child → Widget: The widget below this widget in the tree. [...]
final
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
listenable → Listenable: The Listenable to which this widget is listening. [...]
final, inherited
rect → Animation<RelativeRect>: The animation that controls the child's size and position.
read-only
runtimeType → Type: A representation of the runtime type of the object.
read-only, inherited

Methods

build(BuildContext context) → Widget: Override this method to build widgets that depend on the state of the listenable (e.g., the current value of the animation).
override
createElement() → StatefulElement: Creates a StatefulElement to manage this widget's location in the tree. [...]
inherited
createState() → _AnimatedState: Subclasses typically do not override this method.
inherited
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. [...]
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 DiagnosticsNode.toStringDeep. [...]
inherited
toString({DiagnosticLevel minLevel: DiagnosticLevel.info}) → 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 ==(Object other) → bool: The equality operator. [...]
@nonVirtual, inherited

widgets library

PositionedTransition class

Constructors

Properties

Methods

Operators