[BUG] Crash due to MultipleTapGestureRecognizer

[jhass]

I'm seeing the following crash:

Null check operator used on a null value

Stack trace:

#0 BaseTapGestureRecognizer._checkDown (package:flutter/src/gestures/tap.dart:287)
#1 BaseTapGestureRecognizer.acceptGesture (package:flutter/src/gestures/tap.dart:265)
#2 MultipleTapGestureRecognizer.rejectGesture (package:flutter_html/src/utils.dart:54)
#3 GestureArenaManager._resolve (package:flutter/src/gestures/arena.dart:214)
#4 GestureArenaEntry.resolve (package:flutter/src/gestures/arena.dart:53)
#5 OneSequenceGestureRecognizer.resolve (package:flutter/src/gestures/recognizer.dart:260)
#6 BaseTapGestureRecognizer.resolve (package:flutter/src/gestures/tap.dart:253)
#7 PrimaryPointerGestureRecognizer.handleEvent (package:flutter/src/gestures/recognizer.dart:472)
#8 PointerRouter._dispatch (package:flutter/src/gestures/pointer_router.dart:93)
#9 PointerRouter._dispatchEventToRoutes.<anonymous closure> (package:flutter/src/gestures/pointer_router.dart:138)
#10 _LinkedHashMapMixin.forEach (dart:collection-patch/compact_hash.dart:397)
#11 PointerRouter._dispatchEventToRoutes (package:flutter/src/gestures/pointer_router.dart:136)
#12 PointerRouter.route (package:flutter/src/gestures/pointer_router.dart:122)
#13 GestureBinding.handleEvent (package:flutter/src/gestures/binding.dart:381)
#14 GestureBinding.dispatchEvent (package:flutter/src/gestures/binding.dart:361)
#15 RendererBinding.dispatchEvent (package:flutter/src/rendering/binding.dart:278)
#16 GestureBinding._handlePointerEventImmediately (package:flutter/src/gestures/binding.dart:316)
#17 GestureBinding.handlePointerEvent (package:flutter/src/gestures/binding.dart:280)
#18 GestureBinding._flushPointerEventQueue (package:flutter/src/gestures/binding.dart:238)
#19 GestureBinding._handlePointerDataPacket (package:flutter/src/gestures/binding.dart:221)
#20 _rootRunUnary (dart:async/zone.dart:1370)
#21 _CustomZone.runUnary (dart:async/zone.dart:1265)
#22 _CustomZone.runUnaryGuarded (dart:async/zone.dart:1170)
#23 _invoke1 (dart:ui/hooks.dart:180)
#24 PlatformDispatcher._dispatchPointerDataPacket (dart:ui/platform_dispatcher.dart:276)
#25 _dispatchPointerDataPacket (dart:ui/hooks.dart:96)

This is caused by the current version of MultipleTapGestureRecognizer introduced at #631 and probably originating at https://gist.github.com/Nash0x7E2/08acca529096d93f3df0f60f9c034056

Given the crash happens in Flutter internal state I tried to convince upstream to handle this gracefully but failed to do so: flutter/flutter#82107

Unfortunately my request to suggest a supported solution remained unanswered.

[erickok]

Hmmm. First of all, thanks for the specific and in-depth issue raised. Indeed it seems the internal assertions are not kept with our MultipleTapGestureRecognizer yet it is not entirely clear what the correct approach then is.

I haven't checked in detail yet but believe we use this for cases where both an image tap and link is used?

[jhass]

Yeah, it seems to happen to me if you tap linked images in the wrong way, but not super consistently. It is somewhat race-conditionally.

[tneotia]

I'll have to experiment with this and see what kinds of gestures are in a "passthrough" mode, ie where both the parent and child can see the gesture.

Kind of strange that this functionality isn't supported by flutter, but there may be a workaround.

[tneotia]

Hopefully the above PR is a viable fix for this issue. It does not use any GestureRecognizer workarounds, rather it uses an InheritedWidget.