5。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;