Xamarin.forms: [Bug] X.F 4.0 Grid inside listview throwing null exception

[rohitvipin]

Grid.MeasuredStarredColumns (System.Double widthConstraint, System.Double heightConstraint)

D:\a1\s\Xamarin.Forms.Core\GridCalc.cs, line 436 throws System.NullReferenceException: Object reference not set to an instance of an object.

Steps to Reproduce

1. Create a listview in XAML
2. Use ViewCell and place a Grid inside it with width *
3. Run and navigate to the view

UI is loaded correctly similar to X.F 3.6

Throws Null reference exception

Basic Information

• Version with issue: 4.0.0.425677
• Last known good version: 3.6.0.344457
• IDE: VS2017
• Platform Target Frameworks:
  
  
  
  • iOS: 11.0
  
  
  • Android: 9.0
  
  
• Android Support Library Version: 28.0.0.1
• Nuget Packages:
• Affected Devices: Android

Screenshots

Reproduction Link

[TonyC5]

Observed a related issue in Visual Studio 2019 for Mac / Xamarin. Reverting to Xamarin.Forms.3.6.0.344457 fixes the problem.

• Exception: System.NullReferenceException
• Message: Object reference not set to an instance of an object.
• Source: Xamarin.Forms.Core
• Stack Trace: See attached
  stacktrace.txt

[jepl4052]

Stumbled upon the same issue when upgrading Xamarin Forms from 3.6 to 4, setting Forms.SetFlags("UseLegacyRenderers"); in MainActivity.cs solved the issue (for now) for me.

[TonyC5]

@jepl4052 - Nice work. I saw this MS doc that discusses backward compatibility of Xamarin.Forms Fast Renderers. Looks like this "bug" is actually Xamarin.Forms 4 working as intended.

[samhouts]

Issue6300.zip

@rohitvipin I was unable to reproduce this. Can you please alter the attached solution such that it demonstrates the issue? Thanks!

[PureWeen]

duplicate of https://github.com/xamarin/Xamarin.Forms/issues/6247