CATiledLayer, CALayerDelegate and capturing touch events

Question

How I would go about capturing touch events on a CATiledLayer?

I have the following situation where if I change the view layer to a CATiledLayer the view stops capturing TouchesXXX events. Why does this happens and how should I address this issue.

public partial class DocumentView : UIView
{
    public DocumentView ()
    {
        //if the following lines are removed touch events are captured
        //otherwise they are not
        var tiledLayer = Layer as CATiledLayer;
        tiledLayer.Delegate = new TiledLayerDelegate (this);
    }

    public override void TouchesBegan (NSSet touches, UIEvent evt)
    {
        //does not get called if we hook TiledLayerDelegate up there in the construct  
        base.TouchesBegan (touches, evt);
    }
}

public class TiledLayerDelegate : CALayerDelegate
{
    public DocumentView DocumentView;

    public TiledLayerDelegate (DocumentView documentView)
    {
        DocumentView = documentView;
    }

    public override void DrawLayer (CALayer layer, CGContext context)
    {
        //draw happens here
    }
}

score 2 · Accepted Answer · answered Feb 20 '12 at 17:52

I really do not know what is the reason for this. However, I made it work with two different ways:

By leaving the default type of the layer to CALayer, creating a new CATiledLayer and adding it as a sublayer to the view's Layer. I guess this is not a proper solution.
By using a WeakDelegate, instead of a strongly typed Delegate. Place the following in your view subclass:

[Export("drawLayer:inContext:")]
```
public void DrawLayer(CALayer layer, CGContext context)
{
    //draw happens here 
}
```

and change the following line

tiledLayer.Delegate = new TiledLayerDelegate (this);

to:

tiledLayer.WeakDelegate = this;

CATiledLayer, CALayerDelegate and capturing touch events

1 Answers1