Animated fractionally sized box (#106795)

examples/api/lib/widgets/implicit_animations/animated_fractionally_sized_box.0.dart

+// Copyright 2014 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Flutter code sample for AnimatedFractionallySizedBox
+
+import 'package:flutter/material.dart';
+
+void main() => runApp(const MyApp());
+
+class MyApp extends StatelessWidget {
+  const MyApp({super.key});
+
+  static const String _title = 'Flutter Code Sample';
+
+  @override
+  Widget build(BuildContext context) {
+    return MaterialApp(
+      title: _title,
+      home: Scaffold(
+        appBar: AppBar(title: const Text(_title)),
+        body: const MyStatefulWidget(),
+      ),
+    );
+  }
+}
+
+class MyStatefulWidget extends StatefulWidget {
+  const MyStatefulWidget({super.key});
+
+  @override
+  State<MyStatefulWidget> createState() => _MyStatefulWidgetState();
+}
+
+class _MyStatefulWidgetState extends State<MyStatefulWidget> {
+  bool selected = false;
+
+  @override
+  Widget build(BuildContext context) {
+    return GestureDetector(
+      onTap: () {
+        setState(() {
+          selected = !selected;
+        });
+      },
+      child: Center(
+        child: SizedBox(
+          width: 200,
+          height: 200,
+          child: Container(
+            color: Colors.red,
+            child: AnimatedFractionallySizedBox(
+              widthFactor: selected ? 0.25 : 0.75,
+              heightFactor: selected ? 0.75 : 0.25,
+              alignment: selected ? Alignment.topLeft : Alignment.bottomRight,
+              duration: const Duration(seconds: 1),
+              curve: Curves.fastOutSlowIn,
+              child: Container(
+                color: Colors.blue,
+                child: const FlutterLogo(size: 75),
+              ),
+            ),
+          ),
+        ),
+      ),
+    );
+  }
+}

packages/flutter/lib/src/widgets/basic.dart

@@ -2798,6 +2798,7 @@ class FractionallySizedBox extends SingleChildRenderObjectWidget {
        assert(widthFactor == null || widthFactor >= 0.0),
        assert(heightFactor == null || heightFactor >= 0.0);
 
+  /// {@template flutter.widgets.basic.fractionallySizedBox.widthFactor}
   /// If non-null, the fraction of the incoming width given to the child.
   ///
   /// If non-null, the child is given a tight width constraint that is the max
@@ -2805,8 +2806,10 @@ class FractionallySizedBox extends SingleChildRenderObjectWidget {
   ///
   /// If null, the incoming width constraints are passed to the child
   /// unmodified.
+  /// {@endtemplate}
   final double? widthFactor;
 
+  /// {@template flutter.widgets.basic.fractionallySizedBox.heightFactor}
   /// If non-null, the fraction of the incoming height given to the child.
   ///
   /// If non-null, the child is given a tight height constraint that is the max
@@ -2814,8 +2817,10 @@ class FractionallySizedBox extends SingleChildRenderObjectWidget {
   ///
   /// If null, the incoming height constraints are passed to the child
   /// unmodified.
+  /// {@endtemplate}
   final double? heightFactor;
 
+  /// {@template flutter.widgets.basic.fractionallySizedBox.alignment}
   /// How to align the child.
   ///
   /// The x and y values of the alignment control the horizontal and vertical
@@ -2834,6 +2839,7 @@ class FractionallySizedBox extends SingleChildRenderObjectWidget {
   ///    specify an [AlignmentGeometry].
   ///  * [AlignmentDirectional], like [Alignment] for specifying alignments
   ///    relative to text direction.
+  /// {@endtemplate}
   final AlignmentGeometry alignment;
 
   @override

packages/flutter/lib/src/widgets/implicit_animations.dart

@@ -2108,3 +2108,110 @@ class _AnimatedPhysicalModelState extends AnimatedWidgetBaseState<AnimatedPhysic
     );
   }
 }
+
+/// Animated version of [FractionallySizedBox] which automatically transitions the
+/// child's size over a given duration whenever the given [widthFactor] or
+/// [heightFactor] changes, as well as the position whenever the given [alignment]
+/// changes.
+///
+/// For the animation, you can choose a [curve] as well as a [duration] and the
+/// widget will automatically animate to the new target [widthFactor] or
+/// [heightFactor].
+///
+/// {@tool dartpad}
+/// The following example transitions an [AnimatedFractionallySizedBox]
+/// between two states. It adjusts the [heightFactor], [widthFactor], and
+/// [alignment] properties when tapped, using a [curve] of [Curves.fastOutSlowIn]
+///
+/// ** See code in examples/api/lib/widgets/implicit_animations/animated_fractionally_sized_box.0.dart **
+/// {@end-tool}
+///
+/// See also:
+///
+///  * [AnimatedAlign], which is an implicitly animated version of [Align].
+///  * [AnimatedContainer], which can transition more values at once.
+///  * [AnimatedSlide], which can animate the translation of child by a given offset relative to its size.
+///  * [AnimatedPositioned], which, as a child of a [Stack], automatically
+///    transitions its child's position over a given duration whenever the given
+///    position changes.
+class AnimatedFractionallySizedBox extends ImplicitlyAnimatedWidget {
+  /// Creates a widget that sizes its child to a fraction of the total available
+  /// space that animates implicitly, and positions its child by an alignment
+  /// that animates implicitly.
+  ///
+  /// The [curve] and [duration] argument must not be null
+  /// If non-null, the [widthFactor] and [heightFactor] arguments must be
+  /// non-negative.
+  const AnimatedFractionallySizedBox({
+    super.key,
+    this.alignment = Alignment.center,
+    this.child,
+    this.heightFactor,
+    this.widthFactor,
+    super.curve,
+    required super.duration,
+    super.onEnd,
+  }) : assert(alignment != null),
+       assert(widthFactor == null || widthFactor >= 0.0),
+       assert(heightFactor == null || heightFactor >= 0.0);
+
+  /// The widget below this widget in the tree.
+  ///
+  /// {@macro flutter.widgets.ProxyWidget.child}
+  final Widget? child;
+
+  /// {@macro flutter.widgets.basic.fractionallySizedBox.heightFactor}
+  final double? heightFactor;
+
+  /// {@macro flutter.widgets.basic.fractionallySizedBox.widthFactor}
+  final double? widthFactor;
+
+  /// {@macro flutter.widgets.basic.fractionallySizedBox.alignment}
+  final AlignmentGeometry alignment;
+
+  @override
+  AnimatedWidgetBaseState<AnimatedFractionallySizedBox> createState() => _AnimatedFractionallySizedBoxState();
+
+  @override
+  void debugFillProperties(DiagnosticPropertiesBuilder properties) {
+    super.debugFillProperties(properties);
+    properties.add(DiagnosticsProperty<AlignmentGeometry>('alignment', alignment));
+    properties.add(DiagnosticsProperty<double>('widthFactor', widthFactor));
+    properties.add(DiagnosticsProperty<double>('heightFactor', heightFactor));
+  }
+}
+
+class _AnimatedFractionallySizedBoxState extends AnimatedWidgetBaseState<AnimatedFractionallySizedBox> {
+  AlignmentGeometryTween? _alignment;
+  Tween<double>? _heightFactorTween;
+  Tween<double>? _widthFactorTween;
+
+  @override
+  void forEachTween(TweenVisitor<dynamic> visitor) {
+    _alignment = visitor(_alignment, widget.alignment, (dynamic value) => AlignmentGeometryTween(begin: value as AlignmentGeometry)) as AlignmentGeometryTween?;
+    if(widget.heightFactor != null) {
+      _heightFactorTween = visitor(_heightFactorTween, widget.heightFactor, (dynamic value) => Tween<double>(begin: value as double)) as Tween<double>?;
+    }
+    if(widget.widthFactor != null) {
+      _widthFactorTween = visitor(_widthFactorTween, widget.widthFactor, (dynamic value) => Tween<double>(begin: value as double)) as Tween<double>?;
+    }
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return FractionallySizedBox(
+      alignment: _alignment!.evaluate(animation)!,
+      heightFactor: _heightFactorTween?.evaluate(animation),
+      widthFactor: _widthFactorTween?.evaluate(animation),
+      child: widget.child,
+    );
+  }
+
+  @override
+  void debugFillProperties(DiagnosticPropertiesBuilder description) {
+    super.debugFillProperties(description);
+    description.add(DiagnosticsProperty<AlignmentGeometryTween>('alignment', _alignment, defaultValue: null));
+    description.add(DiagnosticsProperty<Tween<double>>('widthFactor', _widthFactorTween, defaultValue: null));
+    description.add(DiagnosticsProperty<Tween<double>>('heightFactor', _heightFactorTween, defaultValue: null));
+  }
+}

packages/flutter/test/widgets/implicit_animations_test.dart

@@ -421,6 +421,27 @@ void main() {
     expect(state.builds, equals(2));
   });
 
+  testWidgets('AnimatedFractionallySizedBox onEnd callback test', (WidgetTester tester) async {
+    await tester.pumpWidget(wrap(
+      child: TestAnimatedWidget(
+        callback: mockOnEndFunction.handler,
+        switchKey: switchKey,
+        state: _TestAnimatedFractionallySizedBoxWidgetState(),
+      ),
+    ));
+
+    final Finder widgetFinder = find.byKey(switchKey);
+
+    await tester.tap(widgetFinder);
+    await tester.pump();
+    expect(mockOnEndFunction.called, 0);
+    await tester.pump(animationDuration);
+    expect(mockOnEndFunction.called, 0);
+    await tester.pump(additionalDelay);
+    expect(mockOnEndFunction.called, 1);
+
+    await tapTest2and3(tester, widgetFinder, mockOnEndFunction);
+  });
 
   testWidgets('SliverAnimatedOpacity onEnd callback test', (WidgetTester tester) async {
     await tester.pumpWidget(TestAnimatedWidget(
@@ -812,6 +833,19 @@ class _TestAnimatedOpacityWidgetState extends _TestAnimatedWidgetState {
   }
 }
 
+class _TestAnimatedFractionallySizedBoxWidgetState extends _TestAnimatedWidgetState {
+  @override
+  Widget getAnimatedWidget() {
+    return AnimatedFractionallySizedBox(
+      duration: duration,
+      onEnd: widget.callback,
+      heightFactor: toggle ? 0.25 : 0.75,
+      widthFactor: toggle ? 0.25 : 0.75,
+      child: child,
+    );
+  }
+}
+
 class _TestSliverAnimatedOpacityWidgetState extends _TestAnimatedWidgetState {
   @override
   Widget getAnimatedWidget() {