UIPanGestureRecognizer，

UIGestureRecognizer 有：

- (id)initWithTarget:(id)target action:(SEL)action; 

- (void)addTarget:(id)target action:(SEL)action; 

- (void)removeTarget:(id)target action:(SEL)action;

 UIGestureRecognizerState state；

- (CGPoint)locationInView:(UIView*)view;

UIGestureRecognizer 的孩子 有：

   UILongPressGestureRecognizer：

NSUInteger numberOfTapsRequired; 

    UIRotationGestureRecognizer

rotation

velocity

    UISwipeGestureRecognizer

 UISwipeGestureRecognizerDirection direction; 

    UIPanGestureRecognizer

- (CGPoint)translationInView:(UIView *)view; 

- (CGPoint)velocityInView:(UIView *)view; 

    UIPinchGestureRecognizer

 CGFloat velocity;

 CGFloat scale; 

    UITapGestureRecognizer

NSUInteger  numberOfTouchesRequired; 

 NSUInteger  numberOfTapsRequired;