[Bug] CollectionViewRenderer, Control under iOS not of type UICollectionView

[denzerd]

Description

According to the documentations https://docs.microsoft.com/en-us/xamarin/xamarin-forms/app-fundamentals/custom-renderer/renderers#views Xamarin Forms' CollectionView should be of type UICollectionView under iOS. However when implementing a Customrenderer with the help of CollectionViewRenderer the Control is of type UICollectionViewControllerWrapperView. It is difficult or can just be done by tricks to get the actual UICollectionView to manipulate the rendering.

Steps to Reproduce

1. Create a new Xamarin Forms app
2. Create a class inheriting from CollectionView
3. In the iOS project create a custom renderer inheriting from CollectionViewRenderer
4. In the OnElementChanged (Or somewhere you want) print/see the type of Control

Expected Behavior

Control of an iOS CollectionViewRenderer is of type UICollectionView

Actual Behavior

Control of an iOSCollectionViewRenderer is of type UICollectionViewControllerWrapperView

Basic Information

• Version with issue: Xamarin Forms 3.6.0.264807
• Last known good version: /
• IDE: Visual Studio for Mac Community 8.0.5 (build 9)
• Platform Target Frameworks:
  • iOS: Target is 8.0, Device is 12.2

Links

Had a question on the Xamarin community about it already with two workarounds: https://forums.xamarin.com/discussion/156810/ios-collectionviewrenderer-get-uicollectionview#latest

[GalaxiaGuy]

The ViewController property on CollectionViewRenderer is an ItemsViewController, which subclasses UICollectionViewControler. This might allow you to do what you want to do.

It seems actually getting hold of the real UICollectionView being difficult is just a "feature" of iOS:

https://stackoverflow.com/questions/18967928/uicollectionviewcontrollers-layout-ownership-self-collectionview-collectionvie

[denzerd]

@GalaxiaGuy Thanks this is at least an easier way to get the ViewController itself as the two solutions we found In the Xamarin Board.

However the issue persists as the documentation clearly states that the CollectionView is of type UICollectionView under iOS, so either the documentation has to be adjusted or there is something wrong with CollectionViewRenderer under iOS.

Thanks again, good solution for the moment.

[hartez]

Yeah, this is an issue with how iOS structures the classes around UICollectionView. If we actually set Control to be the UICollectionView itself, things get weird with layout; we have to go through the intermediary wrapper control.

I'll see what we can do about noting this in the docs, and possibly adding a more direct property for accessing the UICollectionView itself.

[adrianknight89]

@denzerd There is currently no UICollectionViewControllerWrapperView in the source code as far as I can see. You could currently get the UICollectionView from ItemsViewController.CollectionView property in ItemsViewRenderer. As for the documentation, CollectionViewRenderer is implementing a UIView now. I agree that it should be updated.

[assanesuzy]

Is there any update on this?