showModalBottomSheet should not dispose the controller provided by …

…user (#87707)

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

@@ -497,7 +497,12 @@ class _ModalBottomSheetRoute<T> extends PopupRoute<T> {
   @override
   AnimationController createAnimationController() {
     assert(_animationController == null);
-    _animationController = transitionAnimationController ?? BottomSheet.createAnimationController(navigator!.overlay!);
+    if (transitionAnimationController != null) {
+      _animationController = transitionAnimationController;
+      willDisposeAnimationController = false;
+    } else {
+      _animationController = BottomSheet.createAnimationController(navigator!.overlay!);
+    }
     return _animationController!;
   }
 
@@ -626,7 +631,8 @@ class _BottomSheetSuspendedCurve extends ParametricCurve<double> {
 /// for more details).
 ///
 /// The [transitionAnimationController] controls the bottom sheet's entrance and
-/// exit animations if provided.
+/// exit animations. It's up to the owner of the controller to call
+/// [AnimationController.dispose] when the controller is no longer needed.
 ///
 /// The optional `routeSettings` parameter sets the [RouteSettings] of the modal bottom sheet
 /// sheet. This is particularly useful in the case that a user wants to observe

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

@@ -2794,6 +2794,10 @@ class ScaffoldState extends State<Scaffold> with TickerProviderStateMixin, Resto
   /// [ModalRoute] and a back button is added to the app bar of the [Scaffold]
   /// that closes the bottom sheet.
   ///
+  /// The [transitionAnimationController] controls the bottom sheet's entrance and
+  /// exit animations. It's up to the owner of the controller to call
+  /// [AnimationController.dispose] when the controller is no longer needed.
+  ///
   /// To create a persistent bottom sheet that is not a [LocalHistoryEntry] and
   /// does not add a back button to the enclosing Scaffold's app bar, use the
   /// [Scaffold.bottomSheet] constructor parameter.

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

@@ -149,9 +149,21 @@ abstract class TransitionRoute<T> extends OverlayRoute<T> {
   Animation<double>? get secondaryAnimation => _secondaryAnimation;
   final ProxyAnimation _secondaryAnimation = ProxyAnimation(kAlwaysDismissedAnimation);
 
+  /// Whether to takeover the [controller] created by [createAnimationController].
+  ///
+  /// If true, this route will call [AnimationController.dispose] when the
+  /// controller is no longer needed.
+  /// If false, the controller should be disposed by whoever owned it.
+  ///
+  /// It defaults to `true`.
+  bool willDisposeAnimationController = true;
+
   /// Called to create the animation controller that will drive the transitions to
   /// this route from the previous one, and back to the previous route from this
   /// one.
+  ///
+  /// The returned controller will be disposed by [AnimationController.dispose]
+  /// if the [willDisposeAnimationController] is `true`.
   AnimationController createAnimationController() {
     assert(!_transitionCompleter.isCompleted, 'Cannot reuse a $runtimeType after disposing it.');
     final Duration duration = transitionDuration;
@@ -422,7 +434,9 @@ abstract class TransitionRoute<T> extends OverlayRoute<T> {
   void dispose() {
     assert(!_transitionCompleter.isCompleted, 'Cannot dispose a $runtimeType twice.');
     _animation?.removeStatusListener(_handleStatusChanged);
-    _controller?.dispose();
+    if (willDisposeAnimationController) {
+      _controller?.dispose();
+    }
     _transitionCompleter.complete(_result);
     super.dispose();
   }

packages/flutter/test/material/bottom_sheet_test.dart

@@ -771,6 +771,69 @@ void main() {
     expect(find.text('BottomSheet'), findsNothing);
   });
 
+  // Regression test for https://github.com/flutter/flutter/issues/87592
+  testWidgets('the framework do not dispose the transitionAnimationController provided by user.', (WidgetTester tester) async {
+    const Key tapTarget = Key('tap-target');
+    final AnimationController controller = AnimationController(
+      vsync: const TestVSync(),
+      duration: const Duration(seconds: 2),
+      reverseDuration: const Duration(seconds: 2),
+    );
+
+    await tester.pumpWidget(MaterialApp(
+      home: Scaffold(
+        body: Builder(
+          builder: (BuildContext context) {
+            return GestureDetector(
+              key: tapTarget,
+              onTap: () {
+                showModalBottomSheet<void>(
+                  context: context,
+                  // The default duration and reverseDuration is 1 second
+                  transitionAnimationController: controller,
+                  builder: (BuildContext context) {
+                    return const Text('BottomSheet');
+                  },
+                );
+              },
+              behavior: HitTestBehavior.opaque,
+              child: const SizedBox(
+                height: 100.0,
+                width: 100.0,
+              ),
+            );
+          },
+        ),
+      ),
+    ));
+
+    expect(find.text('BottomSheet'), findsNothing);
+
+    await tester.tap(find.byKey(tapTarget)); // Opening animation will start after tapping
+    await tester.pump();
+
+    expect(find.text('BottomSheet'), findsOneWidget);
+    await tester.pump(const Duration(milliseconds: 2000));
+    expect(find.text('BottomSheet'), findsOneWidget);
+
+    // Tapping above the bottom sheet to dismiss it.
+    await tester.tapAt(const Offset(20.0, 20.0)); // Closing animation will start after tapping
+    await tester.pump();
+
+    expect(find.text('BottomSheet'), findsOneWidget);
+    await tester.pump(const Duration(milliseconds: 2000));
+    // The bottom sheet should still be present at the very end of the animation.
+    expect(find.text('BottomSheet'), findsOneWidget);
+
+    await tester.pump(const Duration(milliseconds: 1));
+    // The bottom sheet should not be showing any longer.
+    expect(find.text('BottomSheet'), findsNothing);
+
+    controller.dispose();
+    // Double disposal will throw.
+    expect(tester.takeException(), isNull);
+  });
+
   testWidgets('Verify persistence BottomSheet use AnimationController if provided.', (WidgetTester tester) async {
     const Key tapTarget = Key('tap-target');
     const Key tapTargetToClose = Key('tap-target-to-close');