提问



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秒钟时,文本double oo被打印两次。为什么是这样?我该怎么办?

最佳参考


UILongPressGestureRecognizer是一个连续的事件识别器。你必须查看状态,看看这是事件的开始,中间还是结束,并采取相应的行动。即你可以在开始后丢弃所有事件,或者只根据需要查看运动。来自班级参考:[15]



  长按手势是连续的。当指定时间段(minimumPressDuration)按下允许的手指数(numberOfTouchesRequired)并且触摸不超出允许的移动范围(allowableMovement)时,手势开始(UIGestureRecognizerStateBegan)。每当手指移动时,手势识别器转换到改变状态,并且当任何手指被抬起时,手势识别器结束(UIGestureRecognizerStateEnded)。



现在你可以追踪像这样的状态


-  (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
     }
  }

其它参考1


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.");
    }
}

其它参考2


您需要检查正确的状态,因为每个州都有不同的行为。很可能你UILongPressGestureRecognizer需要UIGestureRecognizerStateBegan状态。


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
    }
}

其它参考3


试试这个:



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.");
        }
}

其它参考4


这是如何在Swift中处理它:


func longPress(sender:UILongPressGestureRecognizer!) {

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

其它参考5


Swift 3.0:


func handleLongPress(sender: UILongPressGestureRecognizer) {

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

其它参考6


您的手势处理程序接收每个手势状态的调用。所以你需要检查每个状态并将你的代码置于必需的状态。


人们必须更喜欢使用if-else的switch-case:


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;
         }
}