按下时,UILongPressGestureRecognizer会被调用两次

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？

Answer 1

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.也就是说,您可以在开始后丢弃所有事件,或者只根据需要查看运动.从 类参考:

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
     }
  }

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,因为每个州都有不同的行为.很可能你会需要UIGestureRecognizerStateBegan国家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

试试这个:

Objective-C的

- (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 5

以下是在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 6

Swift 3.0:

func handleLongPress(sender: UILongPressGestureRecognizer) {

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

Answer 7

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.

人们必须更喜欢在if-else上使用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;
         }
}