按下时会两次调用UILongPressGestureRecognizer

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？

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。当在指定的时间段（minimumPressDuration）内按下了允许的手指数（numberOfTouchesRequired），并且触摸未移动到允许的移动范围（allowableMovement）范围内时，手势开始（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
     }
  }

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.");
    }
}

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
    }
}

尝试一下：

目标C

- (void)handleLongPress:(UILongPressGestureRecognizer*)sender { 
    if (sender.state == UIGestureRecognizerStateEnded) {
        NSLog(@"Long press Ended");
    } else if (sender.state == UIGestureRecognizerStateBegan) {
        NSLog(@"Long press detected.");
    }
}

Swift 2.2：

func handleLongPress(sender:UILongPressGestureRecognizer) {

        if (sender.state == UIGestureRecognizerState.Ended) {
            print("Long press Ended");
        } else if (sender.state == UIGestureRecognizerState.Began) {
            print("Long press detected.");
        }
}

这是在Swift中处理的方法：

func longPress(sender:UILongPressGestureRecognizer!) {

        if (sender.state == UIGestureRecognizerState.Ended) {
            println("Long press Ended");
        } else if (sender.state == UIGestureRecognizerState.Began) {
            println("Long press detected.");
        }
}

Swift 3.0：

func handleLongPress(sender: UILongPressGestureRecognizer) {

    if sender.state == .ended {
        print("Long press Ended")
    } else if sender.state == .began {
        print("Long press detected")
    }

您的手势处理程序会收到每种手势状态的呼叫。因此，您需要检查每个状态并将代码置于必需状态。

必须使用switch-case而不是if-else：

UILongPressGestureRecognizer *longPress = [[UILongPressGestureRecognizer alloc]
                                         initWithTarget:self 
                                         action:@selector(handleLongPress:)];
    longPress.minimumPressDuration = 1.0;
    [myView addGestureRecognizer:longPress];
    [longPress release];

-(void)handleLongPress:(UILongPressGestureRecognizer *)gesture {
        switch(gesture.state){
          case UIGestureRecognizerStateBegan:
               NSLog(@"State Began");
               break;
          case UIGestureRecognizerStateChanged:
               NSLog(@"State changed");
               break;
          case UIGestureRecognizerStateEnded:
               NSLog(@"State End");
               break;
          default:
               break;
         }
}