Add ability to disable FloatingActionButton scale and rotation anim…

…ations using `FloatingActionButtonAnimator.noAnimation` (#146126)

fixes [[Proposal] Allow disabling the scaling animation of the FloatingActionButton](#145585)

### Using default `FloatingActionButton` animations

![ScreenRecording2024-04-02at16 19 03-ezgif com-video-to-gif-converter](https://github.com/flutter/flutter/assets/48603081/627ea564-7f60-4eb4-bed9-95c053ae2f56)

### Using `FloatingActionButtonAnimator.noAnimation`

![ScreenRecording2024-04-02at16 17 20-ezgif com-video-to-gif-converter](https://github.com/flutter/flutter/assets/48603081/d0a936ea-9e16-4225-8dc4-40a11ee8a975)

examples/api/lib/material/scaffold/scaffold.floating_action_button_animator.0.dart

@@ -0,0 +1,120 @@
+// 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.
+
+import 'package:flutter/material.dart';
+
+/// Flutter code sample for [Scaffold.floatingActionButtonAnimator].
+
+void main() => runApp(const ScaffoldFloatingActionButtonAnimatorApp());
+
+class ScaffoldFloatingActionButtonAnimatorApp extends StatelessWidget {
+  const ScaffoldFloatingActionButtonAnimatorApp({super.key});
+
+  @override
+  Widget build(BuildContext context) {
+    return const MaterialApp(
+      home: ScaffoldFloatingActionButtonAnimatorExample(),
+    );
+  }
+}
+
+enum FabAnimator { defaultStyle, none }
+const List<(FabAnimator, String)> fabAnimatoregments = <(FabAnimator, String)>[
+  (FabAnimator.defaultStyle, 'Default'),
+  (FabAnimator.none, 'None'),
+];
+
+enum FabLocation { centerFloat, endFloat, endTop }
+const List<(FabLocation, String)> fabLocationegments = <(FabLocation, String)>[
+  (FabLocation.centerFloat, 'centerFloat'),
+  (FabLocation.endFloat, 'endFloat'),
+  (FabLocation.endTop, 'endTop'),
+];
+
+class ScaffoldFloatingActionButtonAnimatorExample extends StatefulWidget {
+  const ScaffoldFloatingActionButtonAnimatorExample({super.key});
+
+  @override
+  State<ScaffoldFloatingActionButtonAnimatorExample> createState() => _ScaffoldFloatingActionButtonAnimatorExampleState();
+}
+
+class _ScaffoldFloatingActionButtonAnimatorExampleState extends State<ScaffoldFloatingActionButtonAnimatorExample> {
+  Set<FabAnimator> _selectedFabAnimator = <FabAnimator>{FabAnimator.defaultStyle};
+  Set<FabLocation> _selectedFabLocation = <FabLocation>{FabLocation.endFloat};
+  FloatingActionButtonAnimator? _floatingActionButtonAnimator;
+  FloatingActionButtonLocation? _floatingActionButtonLocation;
+  bool _showFab = false;
+
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+      floatingActionButtonLocation: _floatingActionButtonLocation,
+      floatingActionButtonAnimator: _floatingActionButtonAnimator,
+      appBar: AppBar(title: const Text('FloatingActionButtonAnimator Sample')),
+      body: Center(
+        child: Column(
+          mainAxisAlignment: MainAxisAlignment.center,
+          children: <Widget>[
+            SegmentedButton<FabAnimator>(
+              selected: _selectedFabAnimator,
+              onSelectionChanged: (Set<FabAnimator> styles) {
+                setState(() {
+                  _floatingActionButtonAnimator = switch (styles.first) {
+                    FabAnimator.defaultStyle => null,
+                    FabAnimator.none => FloatingActionButtonAnimator.noAnimation,
+                  };
+                  _selectedFabAnimator = styles;
+                });
+              },
+              segments: fabAnimatoregments
+                .map<ButtonSegment<FabAnimator>>(((FabAnimator, String) fabAnimator) {
+                  final FabAnimator animator = fabAnimator.$1;
+                  final String label = fabAnimator.$2;
+                  return ButtonSegment<FabAnimator>(value: animator, label: Text(label));
+                })
+                .toList(),
+            ),
+            const SizedBox(height: 10),
+            SegmentedButton<FabLocation>(
+              selected: _selectedFabLocation,
+              onSelectionChanged: (Set<FabLocation> styles) {
+                setState(() {
+                  _floatingActionButtonLocation = switch (styles.first) {
+                    FabLocation.centerFloat => FloatingActionButtonLocation.centerFloat,
+                    FabLocation.endFloat => FloatingActionButtonLocation.endFloat,
+                    FabLocation.endTop => FloatingActionButtonLocation.endTop,
+                  };
+                  _selectedFabLocation = styles;
+                });
+              },
+              segments: fabLocationegments
+                .map<ButtonSegment<FabLocation>>(((FabLocation, String) fabLocation) {
+                  final FabLocation location = fabLocation.$1;
+                  final String label = fabLocation.$2;
+                  return ButtonSegment<FabLocation>(value: location, label: Text(label));
+                })
+                .toList(),
+            ),
+            const SizedBox(height: 10),
+            FilledButton.icon(
+              onPressed: () {
+                setState(() {
+                  _showFab = !_showFab;
+                });
+              },
+              icon: Icon(_showFab ? Icons.visibility_off : Icons.visibility),
+              label: const Text('Toggle FAB'),
+            ),
+          ],
+        ),
+      ),
+      floatingActionButton: !_showFab
+        ? null
+        : FloatingActionButton(
+            onPressed: () {},
+            child: const Icon(Icons.add),
+          ),
+    );
+  }
+}

examples/api/test/material/scaffold/scaffold.floating_action_button_animator.0_test.dart

@@ -0,0 +1,60 @@
+// 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.
+
+import 'package:flutter/material.dart';
+import 'package:flutter_api_samples/material/scaffold/scaffold.floating_action_button_animator.0.dart' as example;
+import 'package:flutter_test/flutter_test.dart';
+
+void main() {
+  testWidgets('FloatingActionButton animation can be customized', (WidgetTester tester) async {
+    await tester.pumpWidget(
+      const example.ScaffoldFloatingActionButtonAnimatorApp(),
+    );
+
+    expect(find.byType(FloatingActionButton), findsNothing);
+
+    // Test default FloatingActionButtonAnimator.
+    // Tap the toggle button to show the FAB.
+    await tester.tap(find.text('Toggle FAB'));
+    await tester.pump();
+    await tester.pump(const Duration(milliseconds: 100)); // Advance animation by 100ms.
+    // FAB is partially animated in.
+    expect(tester.getTopLeft(find.byType(FloatingActionButton)).dx, closeTo(743.8, 0.1));
+
+    await tester.pump(const Duration(milliseconds: 100)); // Advance animation by 100ms.
+    // FAB is fully animated in.
+    expect(tester.getTopLeft(find.byType(FloatingActionButton)).dx, equals(728.0));
+
+    // Tap the toggle button to hide the FAB.
+    await tester.tap(find.text('Toggle FAB'));
+    await tester.pump();
+    await tester.pump(const Duration(milliseconds: 100)); // Advance animation by 100ms.
+    // FAB is partially animated out.
+    expect(tester.getTopLeft(find.byType(FloatingActionButton)).dx, closeTo(747.1, 0.1));
+
+    await tester.pump(const Duration(milliseconds: 100)); // Advance animation by 100ms.
+    // FAB is fully animated out.
+    expect(tester.getTopLeft(find.byType(FloatingActionButton)).dx, equals(756.0));
+
+    await tester.pump(const Duration(milliseconds: 50)); // Advance animation by 50ms.
+    // FAB is hidden.
+    expect(find.byType(FloatingActionButton), findsNothing);
+
+    // Select 'None' to disable animation.
+    await tester.tap(find.text('None'));
+    await tester.pump();
+
+    // Test no animation FloatingActionButtonAnimator.
+    await tester.tap(find.text('Toggle FAB'));
+    await tester.pump();
+    // FAB is immediately shown.
+    expect(tester.getTopLeft(find.byType(FloatingActionButton)).dx, equals(728.0));
+
+    // Tap the toggle button to hide the FAB.
+    await tester.tap(find.text('Toggle FAB'));
+    await tester.pump();
+    // FAB is immediately hidden.
+    expect(find.byType(FloatingActionButton), findsNothing);
+  });
+}

packages/flutter/lib/src/material/floating_action_button_location.dart

@@ -937,6 +937,18 @@ abstract class FloatingActionButtonAnimator {
   /// the animation from the beginning, regardless of the original state of the animation.
   double getAnimationRestart(double previousValue) => 0.0;
 
+  /// Creates an instance of [FloatingActionButtonAnimator] where the [FloatingActionButton]
+  /// does not animate on entrance and exit when [FloatingActionButtonLocation] is shown
+  /// or hidden and when transitioning between [FloatingActionButtonLocation]s.
+  ///
+  /// {@tool dartpad}
+  /// This sample showcases how to override [FloatingActionButton] entrance and exit animations
+  /// using [FloatingActionButtonAnimator.noAnimation] in [Scaffold.floatingActionButtonAnimator].
+  ///
+  /// ** See code in examples/api/lib/material/scaffold/scaffold.floating_action_button_animator.0.dart **
+  /// {@end-tool}
+  static const FloatingActionButtonAnimator noAnimation = _NoAnimationFabMotionAnimator();
+
   @override
   String toString() => objectRuntimeType(this, 'FloatingActionButtonAnimator');
 }
@@ -993,6 +1005,25 @@ class _ScalingFabMotionAnimator extends FloatingActionButtonAnimator {
   double getAnimationRestart(double previousValue) => math.min(1.0 - previousValue, previousValue);
 }
 
+class _NoAnimationFabMotionAnimator extends FloatingActionButtonAnimator {
+  const _NoAnimationFabMotionAnimator();
+
+  @override
+  Offset getOffset({required Offset begin, required Offset end, required double progress}) {
+    return end;
+  }
+
+  @override
+  Animation<double> getRotationAnimation({required Animation<double> parent}) {
+    return const AlwaysStoppedAnimation<double>(1.0);
+  }
+
+  @override
+  Animation<double> getScaleAnimation({required Animation<double> parent}) {
+    return const AlwaysStoppedAnimation<double>(1.0);
+  }
+}
+
 /// An animation that swaps from one animation to the next when the [parent] passes [swapThreshold].
 ///
 /// The [value] of this animation is the value of [first] when [parent.value] < [swapThreshold]

packages/flutter/lib/src/material/scaffold.dart

@@ -1436,13 +1436,19 @@ class _FloatingActionButtonTransitionState extends State<_FloatingActionButtonTr
     final Animation<double> moveRotationAnimation = widget.fabMotionAnimator.getRotationAnimation(parent: widget.fabMoveAnimation);
 
     // Aggregate the animations.
-    _previousScaleAnimation = AnimationMin<double>(moveScaleAnimation, _previousExitScaleAnimation!);
-    _currentScaleAnimation = AnimationMin<double>(moveScaleAnimation, _currentEntranceScaleAnimation!);
-    _extendedCurrentScaleAnimation = _currentScaleAnimation.drive(CurveTween(curve: const Interval(0.0, 0.1)));
-
-    _previousRotationAnimation = TrainHoppingAnimation(previousExitRotationAnimation, moveRotationAnimation);
-    _currentRotationAnimation = TrainHoppingAnimation(currentEntranceRotationAnimation, moveRotationAnimation);
+    if (widget.fabMotionAnimator == FloatingActionButtonAnimator.noAnimation) {
+      _previousScaleAnimation = moveScaleAnimation;
+      _currentScaleAnimation = moveScaleAnimation;
+      _previousRotationAnimation = TrainHoppingAnimation(moveRotationAnimation, null);
+      _currentRotationAnimation = TrainHoppingAnimation(moveRotationAnimation, null);
+    } else {
+      _previousScaleAnimation = AnimationMin<double>(moveScaleAnimation, _previousExitScaleAnimation!);
+      _currentScaleAnimation = AnimationMin<double>(moveScaleAnimation, _currentEntranceScaleAnimation!);
+      _previousRotationAnimation = TrainHoppingAnimation(previousExitRotationAnimation, moveRotationAnimation);
+      _currentRotationAnimation = TrainHoppingAnimation(currentEntranceRotationAnimation, moveRotationAnimation);
+    }
 
+    _extendedCurrentScaleAnimation = _currentScaleAnimation.drive(CurveTween(curve: const Interval(0.0, 0.1)));
     _currentScaleAnimation.addListener(_onProgressChanged);
     _previousScaleAnimation.addListener(_onProgressChanged);
   }

packages/flutter/test/material/scaffold_test.dart

@@ -3256,6 +3256,145 @@ void main() {
     // The bottom sheet is dismissed.
     expect(find.byKey(sheetKey), findsNothing);
   });
+
+  // This is a regression test for https://github.com/flutter/flutter/issues/145585.
+  testWidgets('FAB default entrance and exit animations', (WidgetTester tester) async {
+    bool showFab = false;
+
+    await tester.pumpWidget(
+      MaterialApp(
+        home: StatefulBuilder(
+          builder: (BuildContext context, StateSetter setState) {
+            return Scaffold(
+              body: ElevatedButton(
+                onPressed: () {
+                  setState(() {
+                    showFab = !showFab;
+                  });
+                },
+                child: const Text('Toggle FAB'),
+              ),
+              floatingActionButton: !showFab
+                ? null
+                : FloatingActionButton(
+                    onPressed: () {},
+                    child: const Icon(Icons.add),
+                  ),
+            );
+          },
+        ),
+      ),
+    );
+
+    // FAB is not visible.
+    expect(find.byType(FloatingActionButton), findsNothing);
+
+    // Tap the button to show the FAB.
+    await tester.tap(find.widgetWithText(ElevatedButton, 'Toggle FAB'));
+    await tester.pump();
+    await tester.pump(const Duration(milliseconds: 100)); // Advance the animation by 100ms.
+    // FAB is partially animated in.
+    expect(tester.getTopLeft(find.byType(FloatingActionButton)).dx, closeTo(743.8, 0.1));
+
+    await tester.pump(const Duration(milliseconds: 100)); // Advance the animation by 100ms.
+    // FAB is fully animated in.
+    expect(tester.getTopLeft(find.byType(FloatingActionButton)).dx, equals(728.0));
+
+    // Tap the button to hide the FAB.
+    await tester.tap(find.widgetWithText(ElevatedButton, 'Toggle FAB'));
+    await tester.pump();
+    await tester.pump(const Duration(milliseconds: 100)); // Advance the animation by 100ms.
+    // FAB is partially animated out.
+    expect(tester.getTopLeft(find.byType(FloatingActionButton)).dx, closeTo(747.1, 0.1));
+
+    await tester.pump(const Duration(milliseconds: 100)); // Advance the animation by 100ms.
+    // FAB is fully animated out.
+    expect(tester.getTopLeft(find.byType(FloatingActionButton)).dx, equals(756.0));
+
+    await tester.pump(const Duration(milliseconds: 50)); // Advance the animation by 50ms.
+    // FAB is not visible.
+    expect(find.byType(FloatingActionButton), findsNothing);
+  });
+
+  // This is a regression test for https://github.com/flutter/flutter/issues/145585.
+  testWidgets('FAB default entrance and exit animations can be disabled', (WidgetTester tester) async {
+    bool showFab = false;
+    FloatingActionButtonLocation fabLocation = FloatingActionButtonLocation.endFloat;
+
+    await tester.pumpWidget(
+      MaterialApp(
+        home: StatefulBuilder(
+          builder: (BuildContext context, StateSetter setState) {
+            return Scaffold(
+              // Disable FAB animations.
+              floatingActionButtonAnimator: FloatingActionButtonAnimator.noAnimation,
+              floatingActionButtonLocation: fabLocation,
+              body: Column(
+                children: <Widget>[
+                  ElevatedButton(
+                    onPressed: () {
+                      setState(() {
+                        showFab = !showFab;
+                      });
+                    },
+                    child: const Text('Toggle FAB'),
+                  ),
+                  ElevatedButton(
+                    onPressed: () {
+                      setState(() {
+                        fabLocation = FloatingActionButtonLocation.centerFloat;
+                      });
+                    },
+                    child: const Text('Update FAB Location'),
+                  ),
+                ],
+              ),
+              floatingActionButton: !showFab
+                ? null
+                : FloatingActionButton(
+                    onPressed: () {},
+                    child: const Icon(Icons.add),
+                  ),
+            );
+          },
+        ),
+      ),
+    );
+
+    // FAB is not visible.
+    expect(find.byType(FloatingActionButton), findsNothing);
+
+    // Tap the button to show the FAB.
+    await tester.tap(find.widgetWithText(ElevatedButton, 'Toggle FAB'));
+    await tester.pump();
+    // FAB is visible.
+    expect(tester.getTopLeft(find.byType(FloatingActionButton)).dx, equals(728.0));
+
+    // Tap the button to hide the FAB.
+    await tester.tap(find.widgetWithText(ElevatedButton, 'Toggle FAB'));
+    await tester.pump();
+    // FAB is not visible.
+    expect(find.byType(FloatingActionButton), findsNothing);
+
+    // Tap the button to show the FAB.
+    await tester.tap(find.widgetWithText(ElevatedButton, 'Toggle FAB'));
+    await tester.pump();
+    // FAB is visible.
+    expect(tester.getTopLeft(find.byType(FloatingActionButton)).dx, equals(728.0));
+
+    // Tap the update location button.
+    await tester.tap(find.widgetWithText(ElevatedButton, 'Update FAB Location'));
+    await tester.pump();
+
+    // FAB is visible at the new location.
+    expect(tester.getTopLeft(find.byType(FloatingActionButton)).dx, equals(372.0));
+
+    // Tap the button to hide the FAB.
+    await tester.tap(find.widgetWithText(ElevatedButton, 'Toggle FAB'));
+    await tester.pump();
+    // FAB is not visible.
+    expect(find.byType(FloatingActionButton), findsNothing);
+  });
 }
 
 class _GeometryListener extends StatefulWidget {