From 2fff488d60207dc6198e777a4e6caf08f8088bc3 Mon Sep 17 00:00:00 2001
From: Kostia Sokolovskyi <sokolovskyi.konstantin@gmail.com>
Date: Wed, 19 Nov 2025 08:12:19 +0100
Subject: [PATCH] Fix train hopping animation status listeners (#178372)

Fixes https://github.com/flutter/flutter/issues/178336

### Description

- Fixes `TrainHoppingAnimation` to notify status listeners when `status`
changes
- Adds tests

## Pre-launch Checklist

- [X] I read the [Contributor Guide] and followed the process outlined
there for submitting PRs.
- [X] I read the [Tree Hygiene] wiki page, which explains my
responsibilities.
- [X] I read and followed the [Flutter Style Guide], including [Features
we expect every widget to implement].
- [X] I signed the [CLA].
- [X] I listed at least one issue that this PR fixes in the description
above.
- [ ] I updated/added relevant documentation (doc comments with `///`).
- [X] I added new tests to check the change I am making, or this PR is
[test-exempt].
- [X] I followed the [breaking change policy] and added [Data Driven
Fixes] where supported.
- [X] All existing and new tests are passing.

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https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md
[test-exempt]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#tests
[Flutter Style Guide]:
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[Data Driven Fixes]:
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---
 .../flutter/lib/src/animation/animations.dart |  2 +-
 .../test/animation/animations_test.dart       | 28 +++++++++++++++++++
 2 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/packages/flutter/lib/src/animation/animations.dart b/packages/flutter/lib/src/animation/animations.dart
index 3b4d92f235b..924eb9c2e44 100644
--- a/packages/flutter/lib/src/animation/animations.dart
+++ b/packages/flutter/lib/src/animation/animations.dart
@@ -543,7 +543,7 @@ class TrainHoppingAnimation extends Animation<double>
   void _statusChangeHandler(AnimationStatus status) {
     assert(_currentTrain != null);
     if (status != _lastStatus) {
-      notifyListeners();
+      notifyStatusListeners(status);
       _lastStatus = status;
     }
     assert(_lastStatus != null);
diff --git a/packages/flutter/test/animation/animations_test.dart b/packages/flutter/test/animation/animations_test.dart
index f2d063b23b1..d6486c86c72 100644
--- a/packages/flutter/test/animation/animations_test.dart
+++ b/packages/flutter/test/animation/animations_test.dart
@@ -99,7 +99,9 @@ void main() {
 
   test('TrainHoppingAnimation', () {
     final AnimationController currentTrain = AnimationController(vsync: const TestVSync());
+    addTearDown(currentTrain.dispose);
     final AnimationController nextTrain = AnimationController(vsync: const TestVSync());
+    addTearDown(nextTrain.dispose);
     currentTrain.value = 0.5;
     nextTrain.value = 0.75;
     bool didSwitchTrains = false;
@@ -133,6 +135,32 @@ void main() {
     );
   });
 
+  // Regression test for https://github.com/flutter/flutter/issues/178336.
+  test('TrainHoppingAnimation notifies status listeners', () {
+    final AnimationController controller = AnimationController(
+      duration: const Duration(milliseconds: 100),
+      vsync: const TestVSync(),
+    );
+    addTearDown(controller.dispose);
+
+    final TrainHoppingAnimation animation = TrainHoppingAnimation(
+      Tween<double>(begin: 1.0, end: -1.0).animate(controller),
+      Tween<double>(begin: -1.0, end: 1.0).animate(controller),
+    );
+    addTearDown(animation.dispose);
+
+    final List<AnimationStatus> statusLog = <AnimationStatus>[];
+    animation.addStatusListener(statusLog.add);
+    expect(statusLog, isEmpty);
+
+    controller.forward();
+    expect(statusLog, equals(<AnimationStatus>[AnimationStatus.forward]));
+    statusLog.clear();
+
+    controller.reverse();
+    expect(statusLog, equals(<AnimationStatus>[AnimationStatus.dismissed]));
+  });
+
   test('AnimationMean control test', () {
     final AnimationController left = AnimationController(value: 0.5, vsync: const TestVSync());
     final AnimationController right = AnimationController(vsync: const TestVSync());