按下时会两次调用UILongPressGestureRecognizer

Question

我正在检测用户是否已按下2秒钟：UILongPressGestureRecognizer *longPress = [[UILongPressGestureRecognizer alloc]                                             initWithTarget:self                                              action:@selector(handleLongPress:)];        longPress.minimumPressDuration = 2.0;        [self addGestureRecognizer:longPress];        [longPress release];这是我处理长按的方式：-(void)handleLongPress:(UILongPressGestureRecognizer*)recognizer{    NSLog(@"double oo");}当我按下2秒钟以上时，文本“ double oo”被打印两次。为什么是这样？我该如何解决？

Answer 1

UILongPressGestureRecognizer是连续事件识别器。您必须查看状态以查看这是事件的开始，中间还是结束，并采取相应的措施。即，您可以在开始之后放弃所有事件，或者仅根据需要查看运动。从 类参考：

长按手势是连续的。当在指定时间段内（minimumPressDuration）按下了允许的手指数（numberOfTouchesRequired），并且触摸没有移动超出允许的移动范围（allowableMovement）时，手势即开始（UIGestureRecognizerStateBegan）。每当手指移动时，手势识别器都会转换为“更改”状态，并且在任何手指抬起时手势识别器都会终止（UIGestureRecognizerStateEnded）。

现在您可以像这样跟踪状态

-  (void)handleLongPress:(UILongPressGestureRecognizer*)sender { 

    if (sender.state == UIGestureRecognizerStateEnded) {

      NSLog(@"UIGestureRecognizerStateEnded");

    //Do Whatever You want on End of Gesture

     }

    else if (sender.state == UIGestureRecognizerStateBegan){

       NSLog(@"UIGestureRecognizerStateBegan.");

   //Do Whatever You want on Began of Gesture

     }

  }

Answer 2

要检查UILongPressGestureRecognizer的状态，只需在选择器方法上添加if语句：

- (void)handleLongPress:(UILongPressGestureRecognizer *)sender {    

    if (sender.state == UIGestureRecognizerStateEnded) {

        NSLog(@"Long press Ended");

    } else if (sender.state == UIGestureRecognizerStateBegan) {

        NSLog(@"Long press detected.");

    }

}

Answer 3

您需要检查正确的状态，因为每种状态都有不同的行为。您最有可能需要UIGestureRecognizerStateBegan带有状态UILongPressGestureRecognizer。

UILongPressGestureRecognizer *longPress = [[UILongPressGestureRecognizer alloc]

                                             initWithTarget:self 

                                             action:@selector(handleLongPress:)];

longPress.minimumPressDuration = 1.0;

[myView addGestureRecognizer:longPress];

[longPress release];

...

- (void)handleLongPress:(UILongPressGestureRecognizer *)gesture {

    if(UIGestureRecognizerStateBegan == gesture.state) {

        // Called on start of gesture, do work here

    }

    if(UIGestureRecognizerStateChanged == gesture.state) {

        // Do repeated work here (repeats continuously) while finger is down

    }

    if(UIGestureRecognizerStateEnded == gesture.state) {

        // Do end work here when finger is lifted

    }

}