Clear listeners when AnimationController is disposed (#79998)

packages/flutter/lib/src/animation/animation_controller.dart

@@ -801,6 +801,8 @@ class AnimationController extends Animation<double>
     }());
     _ticker!.dispose();
     _ticker = null;
+    clearStatusListeners();
+    clearListeners();
     super.dispose();
   }
 

packages/flutter/lib/src/animation/animations.dart

@@ -589,6 +589,8 @@ class TrainHoppingAnimation extends Animation<double>
     _currentTrain = null;
     _nextTrain?.removeListener(_valueChangeHandler);
     _nextTrain = null;
+    clearListeners();
+    clearStatusListeners();
     super.dispose();
   }
 

packages/flutter/lib/src/animation/listener_helpers.dart

@@ -23,6 +23,7 @@ mixin AnimationLazyListenerMixin {
   ///  * [didUnregisterListener], which may cause the listener list to
   ///    become empty again, and in turn cause this method to call
   ///    [didStartListening] again.
+  @protected
   void didRegisterListener() {
     assert(_listenerCounter >= 0);
     if (_listenerCounter == 0)
@@ -36,6 +37,7 @@ mixin AnimationLazyListenerMixin {
   /// See also:
   ///
   ///  * [didRegisterListener], which causes the listener list to become non-empty.
+  @protected
   void didUnregisterListener() {
     assert(_listenerCounter >= 1);
     _listenerCounter -= 1;
@@ -63,9 +65,11 @@ mixin AnimationLazyListenerMixin {
 /// [AnimationLocalListenersMixin] and [AnimationLocalStatusListenersMixin].
 mixin AnimationEagerListenerMixin {
   /// This implementation ignores listener registrations.
+  @protected
   void didRegisterListener() { }
 
   /// This implementation ignores listener registrations.
+  @protected
   void didUnregisterListener() { }
 
   /// Release the resources used by this object. The object is no longer usable
@@ -87,12 +91,14 @@ mixin AnimationLocalListenersMixin {
   ///
   /// At the time this method is called the registered listener is not yet
   /// notified by [notifyListeners].
+  @protected
   void didRegisterListener();
 
   /// Called immediately after a listener is removed via [removeListener].
   ///
   /// At the time this method is called the removed listener is no longer
   /// notified by [notifyListeners].
+  @protected
   void didUnregisterListener();
 
   /// Calls the listener every time the value of the animation changes.
@@ -113,10 +119,22 @@ mixin AnimationLocalListenersMixin {
     }
   }
 
+  /// Removes all listeners added with [addListener].
+  ///
+  /// This method is typically called from the `dispose` method of the class
+  /// using this mixin if the class also uses the [AnimationEagerListenerMixin].
+  ///
+  /// Calling this method will not trigger [didUnregisterListener].
+  @protected
+  void clearListeners() {
+    _listeners.clear();
+  }
+
   /// Calls all the listeners.
   ///
   /// If listeners are added or removed during this function, the modifications
   /// will not change which listeners are called during this iteration.
+  @protected
   void notifyListeners() {
     final List<VoidCallback> localListeners = List<VoidCallback>.from(_listeners);
     for (final VoidCallback listener in localListeners) {
@@ -161,12 +179,14 @@ mixin AnimationLocalStatusListenersMixin {
   ///
   /// At the time this method is called the registered listener is not yet
   /// notified by [notifyStatusListeners].
+  @protected
   void didRegisterListener();
 
   /// Called immediately after a status listener is removed via [removeStatusListener].
   ///
   /// At the time this method is called the removed listener is no longer
   /// notified by [notifyStatusListeners].
+  @protected
   void didUnregisterListener();
 
   /// Calls listener every time the status of the animation changes.
@@ -187,10 +207,22 @@ mixin AnimationLocalStatusListenersMixin {
     }
   }
 
+  /// Removes all listeners added with [addStatusListener].
+  ///
+  /// This method is typically called from the `dispose` method of the class
+  /// using this mixin if the class also uses the [AnimationEagerListenerMixin].
+  ///
+  /// Calling this method will not trigger [didUnregisterListener].
+  @protected
+  void clearStatusListeners() {
+    _statusListeners.clear();
+  }
+
   /// Calls all the status listeners.
   ///
   /// If listeners are added or removed during this function, the modifications
   /// will not change which listeners are called during this iteration.
+  @protected
   void notifyStatusListeners(AnimationStatus status) {
     final List<AnimationStatusListener> localListeners = List<AnimationStatusListener>.from(_statusListeners);
     for (final AnimationStatusListener listener in localListeners) {

packages/flutter/lib/src/foundation/observer_list.dart

@@ -48,6 +48,13 @@ class ObserverList<T> extends Iterable<T> {
     return _list.remove(item);
   }
 
+  /// Removes all items from the list.
+  void clear() {
+    _isDirty = false;
+    _list.clear();
+    _set.clear();
+  }
+
   @override
   bool contains(Object? element) {
     if (_list.length < 3)

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

@@ -416,6 +416,7 @@ abstract class TransitionRoute<T> extends OverlayRoute<T> {
   @override
   void dispose() {
     assert(!_transitionCompleter.isCompleted, 'Cannot dispose a $runtimeType twice.');
+    _animation?.removeStatusListener(_handleStatusChanged);
     _controller?.dispose();
     _transitionCompleter.complete(_result);
     super.dispose();

packages/flutter/test/animation/animation_controller_listener_test.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.
+
+import 'package:flutter_test/flutter_test.dart';
+import 'package:flutter/scheduler.dart';
+import 'package:flutter/animation.dart';
+
+
+void main() {
+  test('Disposing controller removes listeners to avoid memory leaks', () {
+    final _TestAnimationController controller = _TestAnimationController(
+      duration: const Duration(milliseconds: 100),
+      vsync: const TestVSync(),
+    );
+    int statusListener = 0;
+    int listener = 0;
+    controller.addListener(() {
+      listener++;
+    });
+    controller.addStatusListener((AnimationStatus _) {
+      statusListener++;
+    });
+    expect(statusListener, 0);
+    expect(listener, 0);
+
+    controller.publicNotifyListeners();
+    controller.publicNotifyStatusListeners(AnimationStatus.completed);
+    expect(statusListener, 1);
+    expect(listener, 1);
+
+    controller.dispose();
+    controller.publicNotifyListeners();
+    controller.publicNotifyStatusListeners(AnimationStatus.completed);
+    expect(statusListener, 1);
+    expect(listener, 1);
+  });
+}
+
+class _TestAnimationController extends AnimationController {
+  _TestAnimationController({
+    double? value,
+    Duration? duration,
+    Duration? reverseDuration,
+    String? debugLabel,
+    double lowerBound = 0.0,
+    double upperBound = 1.0,
+    AnimationBehavior animationBehavior = AnimationBehavior.normal,
+    required TickerProvider vsync,
+  }) : super(
+      value: value,
+      duration: duration,
+      reverseDuration: reverseDuration,
+      debugLabel: debugLabel,
+      lowerBound: lowerBound,
+      upperBound: upperBound,
+      animationBehavior: animationBehavior,
+      vsync: vsync,
+  );
+
+  void publicNotifyListeners() {
+    super.notifyListeners();
+  }
+
+  void publicNotifyStatusListeners(AnimationStatus status) {
+    super.notifyStatusListeners(status);
+  }
+}