[Bug] CollectionView.Scrolled event offset isn't correctly reset when items change

[kimbirkelund]

Description

When changing the contents of the CollectionView.ItemsSource while scrolled down into the list, the ItemsViewScrolledEventArgs.VerticalOffset is correctly updated.

Steps to Reproduce

1. Run attached project
2. Press the Fill button
3. Scroll in the list (notice the VerticalOffset label updates to show position)
4. Press Empty button
5. Repeat from 2 at you leasure

Expected Behavior

The value of VerticalOffset should be reset, when pressing Empty, to reflect that the view is no longer scrolled - or at least, as is the case on iOS, the value should be reset the next time scrolling is performed. I'd prefer the former.

Actual Behavior

The value of VerticalOffset on Android keeps incrementing and never returns to 0. On iOS it returns to zero the next time scrolling is performed.

Basic Information

• Version with issue: 4.3.0.851321-pre3
• Last known good version: none

Screenshots

Reproduction Link

App6.zip

[adrianknight89]

I knew this was going to come up at some point. :) See #8018.

[taublast]

Forms 4.7, collectionView gets correct VerticalOffset in OnScrolled event received, after i once refresh the collectionView being inside RefresfView it visually resets ok to zero, but the VerticalOffset in OnScrolled event received is not correct anymore, the minumum it gets is around 6-9.
The position on screen is well 0, but this 0 is reported as a non-zero positive value, the internal calculation might be bugged. That random value is maybe the bouncing offset it had while jumping inside refreshView..

[LittleBoxOfChicken]

Forms 4.8, this issue is still the case on Android. ScrollTo() and changing the ItemSource cause incorrect offsets. Both for HorizontalOffset and VerticalOffset.

[tonyfonager]

And I can confirm on XF 5.0.0.1874 (Android) this is still an issue!

[Cfun1]

@PureWeen I can confirm the issue with wrong scroll offset still happening when adding and then removing the same items, do you suggest reopen this or create another issue ?

[yunusefendi52]

@Cfun1 I think removing items (i.e remove or Clear) is not going to fix vertical offset, according to the test inside the PR #8018 you have to assign new ItemsSource

[valentasm1]

I think it is related to #10966