[Bug] CollectionView is broken on Android, when items have different sizes and ItemSizingStrategy="MeasureAllItems"

[Elashi]

Description

In CollectionView (vertically oriented) when I have items of different sizes , the CollectionView wrongly adds a white/blank space above smaller items. When I scroll back and forth , the white space goes away.

Steps to Reproduce

1. Create a vertical CollectionView with items of different sizes. Make sure you have more items than what the screen fits to make sure scrolling is required.
2. Scroll down to items that are smaller than what is currently displayed
3. A white space will appear before each small item
4. Scroll down a little bit more to hide the erroneous item (until it is completely hidden)
5. Then scroll back up to show the erroneous item . The space will go away.

Expected Behavior

Each item should have the correct height without empty space above.

Actual Behavior

Smaller hidden items are displayed with space above it when we scroll down to them.

Basic Information

• Version with issue: I think it is a regression problem, only appeared in XF 5.0
• Last known good version: XF 4.8
• Platform Target Frameworks:
  • Android: v 10.0

Environment

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Microsoft Visual Studio Community 2019
Version 16.8.4
VisualStudio.16.Release/16.8.4+30907.101
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Version 4.8.04084

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Screenshots

When scrolling down to smaller items, notice the blank area above the last two items:

After scrolling down a little bit more until the erroneous item is hidden up then scroll back up to re show the previous erroneous item, you will notice that the blank space has gone away (I think because it is refreshed). But this only happens for the first erroneous item because I did not scroll down enough to hide the second erroneous item to cause a refresh to it so it kept the white space above it:

This is how it works in XF 4.8:

Worth mentioning

This application is setup to work as a Right To Left application. As you may have noticed from the screenshots.

[Elashi]

By the way, the problem exists in iOS too..

I get bad (and depressing) feedback from my clients for both platforms (iOS and Android) !
This causes a lot of flickering and unstable scrolling also.

[Elashi]

Any news :'-(