按下时 UILongPressGestureRecognizer 被调用两次

Question

我正在检测用户是否按下了 2 秒：

UILongPressGestureRecognizer *longPress = [[UILongPressGestureRecognizer alloc]
                                             initWithTarget:self 
                                             action:@selector(handleLongPress:)];
        longPress.minimumPressDuration = 2.0;
        [self addGestureRecognizer:longPress];
        [longPress release];

这就是我处理长按的方式：

-(void)handleLongPress:(UILongPressGestureRecognizer*)recognizer{
    NSLog(@"double oo");
}

当我按下超过 2 秒时，文本“double oo”会打印两次。这是为什么呢？我该如何修复？

Answer 1

UILongPressGestureRecognizer 是一个连续事件识别器。您必须查看状态，看看这是事件的开始、中间还是结束，并采取相应的行动。即您可以在开始后丢弃所有事件，或者只根据需要查看运动。来自类参考：

长按手势是连续的。当允许的手指数量 (numberOfTouchesRequired) 已按下指定时间段 (minimumPressDuration) 并且触摸移动未超出允许的移动范围 (allowableMovement) 时，手势开始 (UIGestureRecognizerStateBegan)。每当手指移动时，手势识别器就会转换为 Change 状态，并在任何手指抬起时结束 (UIGestureRecognizerStateEnded)。

现在你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，因为每个状态都有不同的行为。您很可能需要 UIGestureRecognizerStateBegan 状态和 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
    }
}

Answer 4

斯威夫特5：

@objc func handleLongPress(sender: UILongPressGestureRecognizer) {
    
    if sender.state == .ended {
        print("Long press Ended")
    } else if sender.state == .began {
        print("Long press detected")
    }
}

Answer 5

试试这个：

Objective-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.");
        }
}

Answer 6

下面是在 Swift 中处理它的方法：

func longPress(sender:UILongPressGestureRecognizer!) {

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

Answer 7

您的手势处理程序接收每个手势状态的调用。因此您需要检查每个状态并将代码置于所需状态。

人们肯定更喜欢使用 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;
         }
}