Xamarin.forms: [Bug] Xamarin.Forms 4.5.0.396 iOS FlexLayout and TemplateSelector issue

[NebulaSleuth]

Description

When using a FlexLayout with a TemplateSelector, rendering of the items in the collection becomes corrupted when switching between different collections.

Steps to Reproduce

1. Create a page with a FlexLayout using BindableLayout.TemplateSelector with at least 2 different DataTemplates
2. Bind the FlexLayout to a collection of objects.
3. After displaying, change the collection of objects

Expected Behavior

Displays each DataTemplate correctly

Actual Behavior

Display is corrupted with overlapping renderings of DataTemplates

Basic Information

• Version with issue:
  4.5.0.396

• Last known good version:
  4.4.0.991757

• IDE: VS 2019 16.4.6

• Platform Target Frameworks:
  
  
  
  • iOS: 13.10.0.21
  
  
  • Android: No Issues
  
  
  • UWP: No Issues
  
  
• Affected Devices: All iOS devices

Screenshots

Reproduction Link

App1.zip

Workaround

Downgrade to Xamarin.Forms 4.4

[NebulaSleuth]

The second image is displaying correctly which occurs when first running. After clicking 'SWAP' button the first image is the result.

[NebulaSleuth]

Also, I have tried:
Xamarin.Forms.Forms.SetFlags("UseLegacyRenderers"); global::Xamarin.Forms.Forms.Init();

But the problem still occurs.

This is a big problem because I need to release my App soon, and Apple is rejecting submissions because of the UIWebView issue, and the fix for that requires 4.5. Catch<->22

[yurkinh]

@NebulaSleuth Workaround is to set "HasShadow=false" for Frame in 4.5.x version. Problem is with Frame not with FlexLayout

[NebulaSleuth]

@yurkinh Thanks it works.