UIView触摸事件touchBegin 等一系列方法

1）手指按下

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event;

2）按下并移动

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event;

3）手指松开

- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event;

4）非正常取消，也就是意外中断

- (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event;