xamarin.ios - PanGestureRecognizer 的有限区域

Question

是否可以为 PanGestureRecognizer 设置边框，使其只能在有限区域/ View 中平移图像？

非常感谢 ;)

Answer 1

您可以实现 UIPanGestureRecognizer 的委托(delegate)方法。检查手势的位置是否在您感兴趣的范围内。对于 should* 方法，您可以返回 false 以取消手势。手势开始后，您可以通过将 State 属性设置为 Cancelled 来取消它。

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;
    }
}