I'm having a problem with ListController.animateToItem inside a child OverlayEntry suddenly calling OverlayEntry.remove.

[gbtb16]

Hi there!

I'm using version 0.4.1 of super_sliver_list.

I have a problem when using an OverlayEntry that has as a child a custom StatefulWidget, we can call it XComponent, which returns a set of items in a CustomScrollView, along with a SuperSliverList.builder.

In XComponent's initState, there is a controller that references an external ValueNotifier that changes when the user highlights an item. Once the highlight changes, it calls ListController.animateToItem to move to the item selected by the text or manually. Visually testing through the app, it's not possible to find the problem. It is seen in my unit tests when selecting an item with the Enter key or left mouse click, which in addition to selecting the item, automatically calls ListController.animateToItem and then closes the overlay and jumps to the next FocusNode.

In question, closing the overlay while selecting an item, which in turn calls ListController.animateToItem, is where the problem lies. The exception thrown is:

First error:

The following assertion was thrown while finalizing the widget tree:
ScrollableState#562f2(tickers: tracking 1 ticker, position:
ScrollPositionWithSingleContext#73217(offset: 0.0, range: 0.0..183.0, viewport: 213.0,
ScrollableState, ClampingScrollPhysics -> RangeMaintainingScrollPhysics, null,
ScrollDirection.idle), effective physics: ClampingScrollPhysics -> RangeMaintainingScrollPhysics)
was disposed with an active Ticker.
ScrollableState created a Ticker via its TickerProviderStateMixin, but at the time dispose() was
called on the mixin, that Ticker was still active. All Tickers must be disposed before calling
super.dispose().
Tickers used by AnimationControllers should be disposed by calling dispose() on the
AnimationController itself. Otherwise, the ticker will leak.
The offending ticker was:
  _WidgetTicker(created by ScrollableState#562f2)
  The stack trace when the _WidgetTicker was actually created was:
  #0      new Ticker.<anonymous closure> (package:flutter/src/scheduler/ticker.dart:71:40)
  #1      new Ticker (package:flutter/src/scheduler/ticker.dart:73:6)
  #2      new _WidgetTicker (package:flutter/src/widgets/ticker_provider.dart)
  #3      TickerProviderStateMixin.createTicker
  (package:flutter/src/widgets/ticker_provider.dart:296:34)
  #4      new AnimationController (package:flutter/src/animation/animation_controller.dart:265:21)
  #5      AnimateToItem.animate (package:super_sliver_list/src/animate_to_item.dart:37:24)

Second error:

══╡ EXCEPTION CAUGHT BY ANIMATION LIBRARY ╞═════════════════════════════════════════════════════════
The following assertion was thrown while notifying listeners for AnimationController:
SuperSliverMultiBoxAdaptorElement unmounted
'package:flutter/src/widgets/framework.dart':
Failed assertion: line 6280 pos 12: '_renderObject != null'

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      RenderObjectElement.renderObject (package:flutter/src/widgets/framework.dart:6280:12)
#3      SliverMultiBoxAdaptorElement.renderObject (package:flutter/src/widgets/sliver.dart:725:57)
#4      SuperSliverMultiBoxAdaptorElement.renderObject (package:super_sliver_list/src/element.dart:28:13)        
#5      SuperSliverMultiBoxAdaptorElement.getOffsetToReveal (package:super_sliver_list/src/element.dart:47:12)   
#6      ExtentManager.getOffsetToReveal (package:super_sliver_list/src/extent_manager.dart:171:21)
#7      AnimateToItem.animate.<anonymous closure> (package:super_sliver_list/src/animate_to_item.dart:47:42)     
#8      AnimationLocalListenersMixin.notifyListeners (package:flutter/src/animation/listener_helpers.dart:161:19)#9      AnimationController._tick (package:flutter/src/animation/animation_controller.dart:865:5)
#10     Ticker._tick (package:flutter/src/scheduler/ticker.dart:258:12)
#11     SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:1386:15)
#12     SchedulerBinding.handleBeginFrame.<anonymous closure> (package:flutter/src/scheduler/binding.dart:1233:11)
#13     _LinkedHashMapMixin.forEach (dart:collection-patch/compact_hash.dart:633:13)
#14     SchedulerBinding.handleBeginFrame (package:flutter/src/scheduler/binding.dart:1231:17)
#15     AutomatedTestWidgetsFlutterBinding.pump.<anonymous closure> (package:flutter_test/src/binding.dart:1265:9)
#18     TestAsyncUtils.guard (package:flutter_test/src/test_async_utils.dart:71:41)
#19     AutomatedTestWidgetsFlutterBinding.pump (package:flutter_test/src/binding.dart:1256:27)
#20     WidgetTester.pumpAndSettle.<anonymous closure> (package:flutter_test/src/widget_tester.dart:712:23)  

Third error:

══╡ EXCEPTION CAUGHT BY FOUNDATION LIBRARY ╞════════════════════════════════════════════════════════
The following assertion was thrown while dispatching notifications for ValueNotifier<int?>:
ListController is not attached.
'package:super_sliver_list/src/super_sliver_list.dart':
Failed assertion: line 130 pos 12: '_delegate != null'

When the exception was thrown, this was the stack:
#2      ListController.animateToItem (package:super_sliver_list/src/super_sliver_list.dart:130:12)
#3      _AutocompleteV2OverlayConteudoItensState._scrollToHighlight (package:lib_flutter_drie/components_layout_v2/autocomplete_v2/components/autocomplete_v2_overlay_conteudo_itens.dart:101:21)
#4      _AutocompleteV2OverlayConteudoItensState._listener (package:lib_flutter_drie/components_layout_v2/autocomplete_v2/components/autocomplete_v2_overlay_conteudo_itens.dart:94:7)
#5      ChangeNotifier.notifyListeners (package:flutter/src/foundation/change_notifier.dart:432:24)
#6      ValueNotifier.value= (package:flutter/src/foundation/change_notifier.dart:554:5)

All the highlighting logic has been tested and proven before, so this wouldn't be your problem.

Studying the case, I imagine the problem is that when an AnimateToItem is created, animate() is called immediately after, but these items are never actually disposed of, resulting in a malfunction when externally forced to exit the loop on its own.

super_sliver_list.dart at 122 line in animateToItem method.

animate_to_item.dart at 28 line in animate method.

[Zekfad]

I'm facing same problem, but i'm using Autocomplete, which causes issues when there is running animation and widget get's removed (user changes text such that widget is removed).

@gbtb16 have you found workaround?

[Zekfad]

I think the issue is that created animation controller is not disposed (leaked) here:

super_sliver_list/lib/src/animate_to_item.dart

Line 41 in a25aa8e

final controller = AnimationController(

[knopp]

The control is disposed when animation is completed

super_sliver_list/lib/src/animate_to_item.dart

Lines 46 to 48 in a25aa8e

	if (status == AnimationStatus.completed) {
	controller.dispose();
	}

And also when the item is removed during animation

super_sliver_list/lib/src/animate_to_item.dart

Lines 57 to 61 in a25aa8e

	if (index == null) {
	controller.stop();
	controller.dispose();
	return;
	}

Is there a codepath where the controller is not disposed?

[Zekfad]

@knopp I've made PR to address this, there is a code path when ListController is detached in mid-animation, which causes Ticker leak.

Animation also needs to be disposed (controller doesn't dispose animations).
Also index is user supplied, so its not really about index being removed, but user saying that it's removed (user has to say that index is no longer valid by returning null).

[gbtb16]

Hi @Zekfad!

Thank you for your comment on my issue and the PR you submitted to try to solve this problem.

My temporary solution was to use the jumpToItem method instead of animateToItem to prevent the animation from happening.

This fixed the bug and produced a faster but less fluid UI since it's basically a teleport when you consider a rotating list using math modules.

I hope your contribution will be reviewed and merged!