Programatically scroll in CollectionView iOS [XAMARIN]

Question

So on Android I have a custom Renderer, for the View. How can I achieve the same on iOS?

[assembly: ExportRenderer(typeof(CustomCollectionView), typeof(CustomCollectionViewRenderer))]
namespace AppTourism.Droid.Renderers
{
    public class CustomCollectionViewRenderer : CollectionViewRenderer, ICustomCollectionViewRenderer
    {

        public void Scroll(int x, int y)
        {
            ScrollBy(x, y);
        }
    }

}

Answer 1

Hello,

You could try to set ContentOffset of the collectionview in iOS, it means the offset for the origin of the content inside a scroll view.

 public void Scroll(int x, int y)  
        {  
            SetContentOffset(new CGPoint(x, y), true);  
        }  

You could also check the scrolling in Xamarin.Forms: https://learn.microsoft.com/en-us/xamarin/xamarin-forms/user-interface/collectionview/scrolling#detect-scrolling

---------UPDATE----------

You need to find the native UICollectionView:

public class CustomCollectionRenderer_iOS : CollectionViewRenderer  
    {  
        UICollectionView nativeCollectionView;  
        protected override void OnElementChanged(ElementChangedEventArgs<GroupableItemsView> e)  
        {  
            base.OnElementChanged(e);  
            if (Control != null)  
            {  
                if (Control.PreferredFocusEnvironments[0] is UICollectionView collectionView)  
                {  
                    nativeCollectionView = Control.PreferredFocusEnvironments[0] as  
                        UICollectionView;// find the native UICollectionView  
                }  
            }  
            UIButton btn = new UIButton();  
            btn.Frame = new CGRect(0, 80, 50, 50);  
            btn.BackgroundColor = UIColor.Red;  
            btn.TouchUpInside += (s, er) =>  
            {  
                Scroll(0, 200);  
            };  
            AddSubview(btn);// click the button to test   
        }  
  
        public void Scroll(int x, int y)  
        {  
            nativeCollectionView.SetContentOffset(new CGPoint(x, y), true);  
        }   
    }  

There is a known issue with how iOS structures the classes around UICollectionView in GitHub, you could follow the progress. You could also try class CollectionViewRenderer : ViewRenderer<CollectionView, UICollectionView>, but in this way, you have to set the native control and custom the UICollectionViewCell and UICollectionViewFlowLayout, refer to https://learn.microsoft.com/en-us/xamarin/ios/user-interface/controls/uicollectionview

 if (Control == null) {  
        SetNativeControl (new UICollectionView (new CGRect (0, 0, 300, 256), new UICollectionViewFlowLayout ()));  
        Control.RegisterClassForCell(typeof(UICollectionViewCell), "MyCell");  
    }  

Best Regards,
Wenyan Zhang

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