Limited Area for PanGestureRecognizer

Question

Is it possible to set borders for a PanGestureRecognizer so it can only pan an image in a limited area/view?

thank you very mutch ;)

Answer 1

You can implement the delegate methods for the UIPanGestureRecognizer. Check to see if the location of the gesture is in the bounds you are interested in. For the should* methods you can return false to cancel the gesture. Once the gesture has been started you can cancel it by setting the State property to Cancelled.

public class GestureView: UIView
{
    RectangleF _bounds;

    public GestureView (RectangleF rect) : base (rect)
    {
        this.BackgroundColor = UIColor.Brown;

        UIPanGestureRecognizer pan = new UIPanGestureRecognizer (this, new Selector ("panViewWithGestureRecognizer:"));
        this.AddGestureRecognizer (pan);
        pan.WeakDelegate = this;
        _bounds = new RectangleF (0,0,200, 100);
    }

    [Export("panViewWithGestureRecognizer:")]
    void PanGestureMoveAround (UIPanGestureRecognizer p)
    {
        if (_bounds.Contains (p.LocationInView (this)))
        {
            Console.WriteLine ("PanGestureMoveAround true");
            return;
        }
        Console.WriteLine ("PanGestureMoveAround false");
        p.State = UIGestureRecognizerState.Cancelled;
        return;
    }

    [Export ("gestureRecognizerShouldBegin:")]
    bool ShouldBegin (UIGestureRecognizer recognizer)
    {
        if (_bounds.Contains (recognizer.LocationInView (recognizer.View)))
        {
            Console.WriteLine ("ShouldBegin true");
            return true;
        }
        Console.WriteLine ("ShouldBegin false");
        return false;
    }

    [Export ("gestureRecognizer:shouldReceiveTouch:")]
    public bool ShouldReceiveTouch (UIGestureRecognizer recognizer, UITouch touch)
    {
        if (_bounds.Contains (touch.LocationInView (recognizer.View)))
        {
            Console.WriteLine ("ShouldReceiveTouch true");
            return true;
        }
        Console.WriteLine ("ShouldReceiveTouch false");
        return false;
    }
}