From cd0082f04f37f2c7e1ea38ac18c235a2184492fa Mon Sep 17 00:00:00 2001
From: Chikamatsu Kazuya <43089218+chika3742@users.noreply.github.com>
Date: Tue, 8 Apr 2025 13:23:34 +0900
Subject: [PATCH] Fix: DraggableScrollableSheet may not close if snapping is
enabled (#165557)
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fixes #140701
This PR fixes an issue where a DraggableScrollableSheet with `snap` set
to true and `shouldCloseOnMinExtent` set to true may not close when
dragged downward.
The issue was caused by round-off errors accumulated by `addPixelDelta`
method, which could lead to `extent.currentSize` not matching the
`extent.minSize` exactly when the bottom is reached. I added logic to
correct it when the snapping ballistic animation is complete.
<details>
<summary>Sample code</summary>
```Dart
import 'package:flutter/material.dart';
void main() {
runApp(MyApp());
}
class MyApp extends StatelessWidget {
const MyApp({super.key});
@override
Widget build(BuildContext context) {
return MaterialApp(
home: HomePage(),
);
}
}
class HomePage extends StatelessWidget {
const HomePage({super.key});
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text("DraggableScrollableSheet Test"),
),
body: Center(
child: ElevatedButton(
child: Text("Open"),
onPressed: () {
showModalBottomSheet(
context: context,
showDragHandle: true,
isScrollControlled: true,
builder: (context) => _buildBottomSheet(),
);
},
),
),
);
}
Widget _buildBottomSheet() {
return NotificationListener<DraggableScrollableNotification>(
onNotification: (notification) {
print(notification.extent);
return false;
},
child: DraggableScrollableSheet(
expand: false,
snap: true,
shouldCloseOnMinExtent: true,
maxChildSize: 0.9,
minChildSize: 0.25,
builder: (context, scrollController) {
return ListView.builder(
controller: scrollController,
itemCount: 100,
itemBuilder: (context, index) {
return ListTile(
title: Text("Item $index"),
);
},
);
},
),
);
}
}
```
</details>
| Before applying fix | After |
| --- | --- |
| * Occurs with probability <video
src="https://github.com/user-attachments/assets/ffd2d097-3ed5-4775-90d5-950092d49591">
| <video
src="https://github.com/user-attachments/assets/0f20cb81-3444-40a3-a84d-ed4bff15887e">
|
## 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.
- [x] 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.
If you need help, consider asking for advice on the #hackers-new channel
on [Discord].
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---
.../widgets/draggable_scrollable_sheet.dart | 20 +++++++++++---
.../draggable_scrollable_sheet_test.dart | 26 +++++++++++++++++++
2 files changed, 42 insertions(+), 4 deletions(-)
diff --git a/packages/flutter/lib/src/widgets/draggable_scrollable_sheet.dart b/packages/flutter/lib/src/widgets/draggable_scrollable_sheet.dart
index 4110266db99..6d0dcc67e97 100644
--- a/packages/flutter/lib/src/widgets/draggable_scrollable_sheet.dart
+++ b/packages/flutter/lib/src/widgets/draggable_scrollable_sheet.dart
@@ -15,6 +15,7 @@ library;
import 'dart:math' as math;
+import 'package:collection/collection.dart';
import 'package:flutter/foundation.dart';
import 'package:flutter/gestures.dart';
@@ -909,14 +910,18 @@ class _DraggableScrollableSheetScrollPosition extends ScrollPositionWithSingleCo
}
}
- bool get _isAtSnapSize {
- return extent.snapSizes.any((double snapSize) {
+ // Checks if the sheet's current size is close to a snap size, returning the
+ // snap size if so; returns null otherwise.
+ double? _getCurrentSnapSize() {
+ return extent.snapSizes.firstWhereOrNull((double snapSize) {
return (extent.currentSize - snapSize).abs() <=
extent.pixelsToSize(physics.toleranceFor(this).distance);
});
}
- bool get _shouldSnap => extent.snap && extent.hasDragged && !_isAtSnapSize;
+ bool _isAtSnapSize() => _getCurrentSnapSize() != null;
+
+ bool _shouldSnap() => extent.snap && extent.hasDragged && !_isAtSnapSize();
@override
void dispose() {
@@ -929,7 +934,7 @@ class _DraggableScrollableSheetScrollPosition extends ScrollPositionWithSingleCo
@override
void goBallistic(double velocity) {
- if ((velocity == 0.0 && !_shouldSnap) ||
+ if ((velocity == 0.0 && !_shouldSnap()) ||
(velocity < 0.0 && listShouldScroll) ||
(velocity > 0.0 && extent.isAtMax)) {
super.goBallistic(velocity);
@@ -981,6 +986,13 @@ class _DraggableScrollableSheetScrollPosition extends ScrollPositionWithSingleCo
super.goBallistic(velocity);
ballisticController.stop();
} else if (ballisticController.isCompleted) {
+ // Update the extent value after the snap animation completes to
+ // avoid rounding errors that could prevent the sheet from closing when
+ // it reaches minSize.
+ final double? snapSize = _getCurrentSnapSize();
+ if (snapSize != null) {
+ extent.updateSize(snapSize, context.notificationContext!);
+ }
super.goBallistic(0);
}
}
diff --git a/packages/flutter/test/widgets/draggable_scrollable_sheet_test.dart b/packages/flutter/test/widgets/draggable_scrollable_sheet_test.dart
index 4f44965fba0..47a2c295fb8 100644
--- a/packages/flutter/test/widgets/draggable_scrollable_sheet_test.dart
+++ b/packages/flutter/test/widgets/draggable_scrollable_sheet_test.dart
@@ -1892,4 +1892,30 @@ void main() {
expect(receivedNotification!.shouldCloseOnMinExtent, isFalse);
controller.dispose();
});
+
+ // Regression test for https://github.com/flutter/flutter/issues/140701
+ testWidgets('DraggableScrollableSheet snaps exactly to minChildSize', (
+ WidgetTester tester,
+ ) async {
+ double? lastExtent;
+
+ await tester.pumpWidget(
+ boilerplateWidget(
+ null,
+ snap: true,
+ onDraggableScrollableNotification: (DraggableScrollableNotification notification) {
+ lastExtent = notification.extent;
+ return false;
+ },
+ ),
+ );
+
+ // One of the conditions for reproducing the round-off error.
+ await tester.fling(find.text('Item 1'), const Offset(0, 100), 2000);
+ await tester.pumpFrames(
+ tester.widget(find.byType(Directionality)),
+ const Duration(milliseconds: 500),
+ );
+ expect(lastExtent, .25);
+ });
}
--
GitLab