Grouped CollectionView fires IndexOutOfBoundsException from MauiRecyclerView after second collapse/expand

[mattkeene]

Description

In an Android / iOS MAUI application, one of my pages implements an expandable/collapsible CollectionView bound to an ObservableCollection<ProtocolGroup>. ProtocolGroup is an extension of ObservableRangeCollection<Protocol> with properties for IsCollapsed, GroupName, and DropdownText (arrow-icon that changes on collapse). ProtocolGroup also implements INotifyPropertyChanged, for when IsCollapsed and DropdownText change. ObservableRangeCollection handles the notifications for AddRange() and Clear(), the methods I use to collapse/expand each group by removing or adding Protocol objects from the full list. I originally used List<Protocol> for the items in each group (more info in workaround section) but this results in the groups not animating on collapse/expand.

I created a fresh repo (linked below) using only the classes necessary for this single CollectionView, and the issue persists. The primary ObservableCollection<ProtocolGroup> does not change after initialization (no groups are added/removed) and therefore I originally had it as a List<ProtocolGroup> which resulted in the same exact behavior, so I Ieft it as an ObservableCollection in the attached repo.

All groups begin collapsed and everything works at first. I can expand all the groups, and collapse all the groups. However, when I expand a group that has previously been collapsed (e.g the second expansion) an Java.Lang.IndexOutOfBoundsException: is thrown from the MauiRecyclerView (full error pasted below in the log output) and my application crashes. Since everything is in sync for the first expand/collapse, what could be going wrong afterwards?

Steps to Reproduce

1. Run the repo on an Android simulator or device
2. Tap a few groups to expand
3. Tap them again to collapse
4. Tap any one you manually collapsed

Expected outcome: The group should expand again
Actual outcome: The exception in the log output is thrown and the application crashes

Link to public reproduction project repository

https://github.com/mattkeene/CollectionViewBugRepro

Version with bug

8.0.40 SR5

Is this a regression from previous behavior?

Not sure, did not test other versions

Last version that worked well

Unknown/Other

Affected platforms

iOS, Android

Affected platform versions

Android 14.0 - API 34

Did you find any workaround?

By changing ProtocolGroup to be an extension of List<Protocol> which implements INotifyPropertyChanged and INotifyCollectionChanged, I can manually "new" the Clear() and AddRange() methods of List<Protocol> to call the base versions followed by calling RaiseCollectionChanged() and RaisedPropertyChanged() (on Count, Items[], and DropdownText) which invoke them, respectively. This results in functional collapsible/expandable groups without exceptions/crashes, BUT it does not animate the collapsing/expanding which hinders the user experience as the lists simply appear and disappear starkly. By using ObservableRangeCollection<Protocol>, the expanding/collapsing is animated as expected, but crashes on second expand.

Relevant log output

**Java.Lang.IndexOutOfBoundsException:** 'Inconsistency detected. Invalid view holder adapter positionTemplatedItemViewHolder{cf38be1 position=37 id=-1, oldPos=17, pLpos:17 scrap [attachedScrap] tmpDetached no parent} crc645d80431ce5f73f11.MauiRecyclerView_3{efa7858 VFED..... ......ID 0,0-1080,2054}, adapter:crc645d80431ce5f73f11.ReorderableItemsViewAdapter_2@2f947d2, layout:androidx.recyclerview.widget.LinearLayoutManager@3a8a788, context:crc642c18c1b741c10a87.MainActivity@de5472c'

[github-actions]

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Please view the issues below to see if they solve your problem, and if the issue describes your problem please consider closing this one and thumbs upping the other issue to help us prioritize it. Thank you!

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[PureWeen]

Duplicate of #20819

[mattkeene]

For anyone that comes to this after the fact, a temporary workaround until the component is fixed is use while (groupToCollase.Count > 0) groupToCollapse.RemoveAt(0) in place of groupToCollapse.Clear() until the group is empty. It slows the application down because of all the extra events, but it avoids crashing. This is only needed on Android.