Building a VisualElementRenderer for iOS

To handle native touch events on iOS, we are going to build a VisualElementRenderer. These work similar to CustomRenderers, but instead of rendering and replacing the entire control, we are able to render specific attributes, so we are able to attach native attributes to a Xamarin.Forms view.

Let's start with adding a new folder inside the Renderers folder called FocusView. Add in a new file called FocusViewRendererTouchAttribute.cs and implement the following:

public class FocusViewRendererTouchAttribute : VisualElementRenderer<FocusView> 
    { 
        public override void TouchesBegan (NSSet touches, UIEvent evt) 
        { 
            base.TouchesBegan (touches, evt); 
 
            FocusView focusView = ((FocusView)this.Element); 
 
            UITouch touch = touches.AnyObject as UITouch; 
 
            if (touch != null)  
            { 
                var posc = touch.LocationInView (touch.View); 
                focusView.NotifyFocus...