UIView－双击手势和单击手势的区别

iOS中识别双击事件的做法：

创建UITapGestureRecognizer对象,设置numberOfTapsRequired的值为2，

UITapGestureRecognizer *doubleTapRecognizer =

            [[UITapGestureRecognizer alloc] initWithTarget:self

                                                    action:@selector(doubleTap:)];

        doubleTapRecognizer.numberOfTapsRequired = 2;

        [self addGestureRecognizer:doubleTapRecognizer];

action 函数

  - (void)doubleTap:(UIGestureRecognizer *)gr

   {

       NSLog(@"Recognized Double Tap");

   }

同一个UIView中，实现了touchesBegan函数

// 触摸开始
-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    NSLog(@"touch begin");
}

问题

双击后，查看日志.发现触摸事件发生的顺序如下：

2015-09-15 21:57:55.249 TouchTracker[20387:5622651] touch begin

2015-09-15 21:57:55.421 TouchTracker[20387:5622651] double tap

这是因为用户点击屏幕时，UIView会收到在touchesBegan:withEvent 消息。在UIGestureRecognizer识别出双击手势之前，UIView会收到touchesBegan:withEvent 消息；在识别UIGestureRecognizer识别出双击手势之后，UIGestureRecognizer会自行处理相关触摸事件，触摸事件所引起的UIResponder消息将不再发送给UIView。直到UIGestureRecognizer检测出点击手势已经结束，UIView才会重新受到UIResponder消息。

解决

需要在识别出点击手势之前，避免向UIView发送touchBegin:withEvent消息。delaysTouchesBegan值设为YES。

UITapGestureRecognizer * doubleTapRecognizer=

        [[UITapGestureRecognizer alloc]initWithTarget:self action:@selector(doubleTap:)];

        doubleTapRecognizer.numberOfTapsRequired=2;

        doubleTapRecognizer.delaysTouchesBegan=YES; 

        [self addGestureRecognizer:doubleTapRecognizer];

区别双击和单击

增加单次点击识别

// single tap

        UITapGestureRecognizer *tapRecognizer=

        [[UITapGestureRecognizer alloc]initWithTarget:self action:@selector(tap:)];

        [self addGestureRecognizer:tapRecognizer];

action函数

-(void)tap:(UIGestureRecognizer *) gr

{

    NSLog(@"tap");

}

查看日志输出的时候，发现，点击两次的时候，UIView无法识别单击事件和双击事件。tap：和 doubleTap：都会执行。

2015-09-15 22:36:02.441 TouchTracker[20631:5667414] tap

2015-09-15 22:36:02.600 TouchTracker[20631:5667414] double tap

因为双击事件包含两次单击事件，所以第一次点击被识别为单击事件。

解决方法

设置在单击后暂时不进行识别(稍作停顿)，直到确定不是双击事件后再识别为单击事件。

// single tap

        UITapGestureRecognizer *tapRecognizer=

        [[UITapGestureRecognizer alloc]initWithTarget:self action:@selector(tap:)];

        [tapRecognizer requireGestureRecognizerToFail:doubleTapRecognizer];

        [self addGestureRecognizer:tapRecognizer];