GestureDetector in ListView is not working

[JohannesKaufmann]

Describe the bug I have a ListView with items similar to the scroll example (which is now working really great by the way 👍). Every item is wrapped in a GestureDetector that is listening for onTap.

There are currently three problems:

• The taps are oftentimes not regognized.
• If onTap is successfully called, the sheet jumps around.
• There is also sometimes the following message appearing in the console

  flutter: ══╡ EXCEPTION CAUGHT BY GESTURE ╞═══════
  flutter: The following assertion was thrown while handling a gesture:
  flutter: 'package:rubber/src/bottom_sheet.dart': Failed assertion: line 149 pos 12: '_hold == null': is not
  flutter: true.
  flutter:
  flutter: Either the assertion indicates an error in the framework itself, or we should provide substantially
  flutter: more information in this error message to help you determine and fix the underlying cause.
  flutter: In either case, please report this assertion by filing a bug on GitHub:
  flutter:   https://github.com/flutter/flutter/issues/new?template=BUG.md
  flutter:
  flutter: When the exception was thrown, this was the stack:
  flutter: #2      _RubberBottomSheetState._onVerticalDragDown (package:rubber/src/bottom_sheet.dart:149:12)
  flutter: #3      DragGestureRecognizer.addPointer.<anonymous closure> (package:flutter/src/gestures/monodrag.dart:123:46)
  flutter: #4      GestureRecognizer.invokeCallback (package:flutter/src/gestures/recognizer.dart:102:24)
  flutter: #5      DragGestureRecognizer.addPointer (package:flutter/src/gestures/monodrag.dart:123:9)
  flutter: #6      RawGestureDetectorState._handlePointerDown (package:flutter/src/widgets/gesture_detector.dart:643:18)
  flutter: #7      RenderPointerListener.handleEvent (package:flutter/src/rendering/proxy_box.dart:2500:14)
  flutter: #8      _WidgetsFlutterBinding&BindingBase&GestureBinding.dispatchEvent (package:flutter/src/gestures/binding.dart:158:22)
  flutter: #9      _WidgetsFlutterBinding&BindingBase&GestureBinding._handlePointerEvent (package:flutter/src/gestures/binding.dart:138:7)
  flutter: #10     _WidgetsFlutterBinding&BindingBase&GestureBinding._flushPointerEventQueue (package:flutter/src/gestures/binding.dart:101:7)
  flutter: #11     _WidgetsFlutterBinding&BindingBase&GestureBinding._handlePointerDataPacket (package:flutter/src/gestures/binding.dart:85:7)
  flutter: #12     _invoke1 (dart:ui/hooks.dart:168:13)
  flutter: #13     _dispatchPointerDataPacket (dart:ui/hooks.dart:122:5)
  flutter: (elided 2 frames from class _AssertionError)
  flutter:
  flutter: Handler: onDown
  flutter: Recognizer:
  flutter:   VerticalDragGestureRecognizer#d7641(debugOwner: GestureDetector)
  flutter: ═══════

Expected behavior I expect that "normal" interactions like onTap are handled by the widgets inside of the modal.

[mcrovero]

Thanks, really appreciated! Check the latest version, it should be fixed.

[JohannesKaufmann]

Great, that was fast! Taps are now properly recognized and the warning is not appearing anymore.

But as soon as it's "expanded" and an item is tapped, it is jumping: The list is animated to a position further up and then animated back to the "expanded" position.

I have two detectors:

• a GestureDetector wrapping the whole item.
• a TapGestureRecognizerinside a TextSpan. It it inside the GestureDetector and only fills a small amount of space.

What's weird is that when the TapGestureRecognizer detects a onTap the list is not jumping. It only happens with the GestureDetector (it's probably due to it's size). And when the sheet is not fully expanded that jumping does not appear at all.

[mcrovero]

I can't reproduce the error, could you please share the skeleton of your widgets?

[JohannesKaufmann]

I just another look at my code. I still had a _controller.launchTo(AnimationState.half_expanded); in the onTap. Sorry that was my fault 😂.

So the bug is actually that launchTo only works for animating upwards (collapsed -> half_expanded -> expanded). And not the other way around (for example collapsing it again). Sorry for wasting your time...

[mcrovero]

No problem 😄 Thanks for your help!

[LcTwisk]

I'm facing the same problem where taps are not always recognised by the GestureDetector that's used inside a ListView. I'm currently on: rubber: ^0.3.2

I'll prepare an example project so you can reproduce it ;)