/**

 *  触摸开始(手指刚碰到view)

 */

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

/**

 *  触摸ing(手指在view上面挪来挪去)

 */

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

{

    UITouch *touch = [touches anyObject];

    // 当前触摸点

    CGPoint current = [touch locationInView:self];

    // 上一个触摸点

    CGPoint previous = [touch previousLocationInView:self];

    // 修改当前view的位置(中点)

    CGPoint center = self.center;

    center.x += current.x - previous.x;

    center.y += current.y - previous.y;

    self.center = center;

}

/**

 *  触摸结束(手指离开view)

 */

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

/**

 *  触摸手势取消(比如说来电时，手势也就中断了)

 */

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