Assertion Error using CustomScrollView with CupertinoSliverNavigationBar (Flutter 3.29) #163297
Description
Steps to reproduce
When scrolling on the CupertinoSliverNavigationBar, an assertion error occurs randomly. The issue arises after performing multiple scroll gestures on the navigation bar in both directions. The following assertion errors are thrown:
'package:flutter/src/widgets/scrollable.dart': Failed assertion: line 875 pos 12: '_hold == null': is not true.
'package:flutter/src/widgets/scrollable.dart': Failed assertion: line 880 pos 12: '_hold == null || _drag == null': is not true.Steps to Reproduce:
- Run the provided code.
- Scroll up or down on the navigation bar multiple times.
- Observe the assertion errors in the debug console.
- Attempt to scroll again—scrolling is now completely broken.
Code:
void main() {
runApp(const MyApp());
}
class MyApp extends StatelessWidget {
const MyApp({super.key});
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
colorScheme: ColorScheme.fromSeed(seedColor: Colors.deepPurple),
),
home: Scaffold(
body: CustomScrollView(
slivers: [
CupertinoSliverNavigationBar(
largeTitle: Text("Example"),
),
],
),
),
);
}
}Expected results
Regardless of the scrolling movement, no errors should be thrown.
Actual results
Assertion errors occur, and the scrolling state becomes unresponsive.
Code sample
Example
void main() {
runApp(const MyApp());
}
class MyApp extends StatelessWidget {
const MyApp({super.key});
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
colorScheme: ColorScheme.fromSeed(seedColor: Colors.deepPurple),
),
home: Scaffold(
body: CustomScrollView(
slivers: [
CupertinoSliverNavigationBar(
largeTitle: Text("Example"),
),
],
),
),
);
}
}Screenshots or Video
Screenshots / Video demonstration
413289971-3b229b1f-37b1-418d-9fbd-dc95be1ec686.mov
Logs
Logs
======== Exception caught by gesture ===============================================================
The following assertion was thrown while handling a gesture:
'package:flutter/src/widgets/scrollable.dart': Failed assertion: line 875 pos 12: '_hold == null': is not true.
Either the assertion indicates an error in the framework itself, or we should provide substantially more information in this error message to help you determine and fix the underlying cause.
In either case, please report this assertion by filing a bug on GitHub:
https://github.com/flutter/flutter/issues/new?template=2_bug.yml
When the exception was thrown, this was the stack:
#2 ScrollableState._handleDragStart (package:flutter/src/widgets/scrollable.dart:875:12)
#3 DragGestureRecognizer._checkStart.<anonymous closure> (package:flutter/src/gestures/monodrag.dart:849:53)
#4 GestureRecognizer.invokeCallback (package:flutter/src/gestures/recognizer.dart:357:24)
#5 DragGestureRecognizer._checkStart (package:flutter/src/gestures/monodrag.dart:849:7)
#6 DragGestureRecognizer._checkDrag (package:flutter/src/gestures/monodrag.dart:815:5)
#7 DragGestureRecognizer.acceptGesture (package:flutter/src/gestures/monodrag.dart:743:7)
#8 GestureArenaManager._resolveByDefault (package:flutter/src/gestures/arena.dart:275:25)
#9 GestureArenaManager._tryToResolveArena.<anonymous closure> (package:flutter/src/gestures/arena.dart:255:31)
(elided 4 frames from class _AssertionError and dart:async)
Handler: "onStart"
Recognizer: VerticalDragGestureRecognizer#42451
start behavior: start
====================================================================================================
======== Exception caught by gesture ===============================================================
The following assertion was thrown while handling a gesture:
'package:flutter/src/widgets/scrollable.dart': Failed assertion: line 880 pos 12: '_hold == null || _drag == null': is not true.
Either the assertion indicates an error in the framework itself, or we should provide substantially more information in this error message to help you determine and fix the underlying cause.
In either case, please report this assertion by filing a bug on GitHub:
https://github.com/flutter/flutter/issues/new?template=2_bug.yml
When the exception was thrown, this was the stack:
#2 ScrollableState._handleDragUpdate (package:flutter/src/widgets/scrollable.dart:880:12)
#3 DragGestureRecognizer._checkUpdate.<anonymous closure> (package:flutter/src/gestures/monodrag.dart:868:55)
#4 GestureRecognizer.invokeCallback (package:flutter/src/gestures/recognizer.dart:357:24)
#5 DragGestureRecognizer._checkUpdate (package:flutter/src/gestures/monodrag.dart:868:7)
#6 DragGestureRecognizer.handleEvent (package:flutter/src/gestures/monodrag.dart:714:11)
#7 PointerRouter._dispatch (package:flutter/src/gestures/pointer_router.dart:97:12)
#8 PointerRouter._dispatchEventToRoutes.<anonymous closure> (package:flutter/src/gestures/pointer_router.dart:143:9)
#9 _LinkedHashMapMixin.forEach (dart:_compact_hash:763:13)
#10 PointerRouter._dispatchEventToRoutes (package:flutter/src/gestures/pointer_router.dart:141:18)
#11 PointerRouter.route (package:flutter/src/gestures/pointer_router.dart:131:7)
#12 GestureBinding.handleEvent (package:flutter/src/gestures/binding.dart:530:19)
#13 GestureBinding.dispatchEvent (package:flutter/src/gestures/binding.dart:499:22)
#14 RendererBinding.dispatchEvent (package:flutter/src/rendering/binding.dart:460:11)
#15 GestureBinding._handlePointerEventImmediately (package:flutter/src/gestures/binding.dart:437:7)
#16 GestureBinding.handlePointerEvent (package:flutter/src/gestures/binding.dart:394:5)
#17 GestureBinding._flushPointerEventQueue (package:flutter/src/gestures/binding.dart:341:7)
#18 GestureBinding._handlePointerDataPacket (package:flutter/src/gestures/binding.dart:308:9)
#19 _invoke1 (dart:ui/hooks.dart:332:13)
#20 PlatformDispatcher._dispatchPointerDataPacket (dart:ui/platform_dispatcher.dart:451:7)
#21 _dispatchPointerDataPacket (dart:ui/hooks.dart:267:31)
(elided 2 frames from class _AssertionError)
Handler: "onUpdate"
Recognizer: VerticalDragGestureRecognizer#42451
start behavior: start
====================================================================================================Flutter Doctor output
Doctor output
[✓] Flutter (Channel stable, 3.29.0, on macOS 15.3 24D60 darwin-arm64, locale de-DE) [1.836ms]
• Flutter version 3.29.0 on channel stable at /Users/***
• Upstream repository https://github.com/flutter/flutter.git
• Framework revision 35c388afb5 (4 days ago), 2025-02-10 12:48:41 -0800
• Engine revision f73bfc4522
• Dart version 3.7.0
• DevTools version 2.42.2