Xamarin.forms: [Bug] Xamarin Forms 4 regression: ListView display glitches

[mfeingol]

Description

Set up a grouped listview where tapping a group title toggles the presence/absence of content in the group. If you tap on groups enough, you'll start seeing glitches in how the ListView displays its content, like random whitespace replacing collapsed group titles.

This same scenario works fine with XF 3.6.0 with the FastRenderers_Experimental flag enabled.

I should add that this isn't just glitches. With a larger sample data set than the repro below, I was able to verify that TapGestureRecognizer.Tapped events were being delivered for different group model instances than the ones being tapped, implying that the groups being displayed were entirely out of sync with the XF4 ListView's internal state.

Steps to Reproduce

Use the project referenced below. Tap around on the dates (titles) until you observe the kinds of glitches present in the screenshot below. And apologies for the ugliness and complexity of the repro.

Expected Behavior

No visual glitches.

Actual Behavior

Glitches

Basic Information

• Version with issue: 4.0.0.425677
• Last known good version: 3.6.0
• IDE: VS 2019 16.1.1
• Platform Target Frameworks:
  
  
  
  • Android: 9.0
  
  
• Android Support Library Version: 28.0.0.1
• Nuget Packages:
• Affected Devices:

Screenshots

See above.

Reproduction Link

https://github.com/mfeingol/repros/tree/master/ListViewIssuesXF4

[paymicro]

Hi @mfeingol
Could you test with the attached nuget?

[mfeingol]

@paymicro: I tested this morning with your 9.9.4 package and I believe it fixes the problem. Kudos.

[mfeingol]

A note... this isn't fixed in 4.0.0.482894.

[LeoJHarris]

Yes we are seeing the same issue in CollectionView and also ListView, Views are disappearing and not reappearing.

In the below all views should have data populated but rather some views are missing have disappeared and scrolling up and down randomly causes some views to disappear as well. This is quite an issue.

[jennablackwell]

This is happening to me as well with the latest nuget. Items in the listview when you scroll will sometimes disappear.

[mfeingol]

@paymicro: any luck getting a fix into an official XF4 release?

[toomasz]

Hopefully this can be fixed soon

[samhouts]

closed by #6390