轻按一下手势识别器

Question

I am trying to use this code for a tap gesture recognizer, it works fine when number of taps required is set to 2, but when I set the number of taps required to 1 it stop functioning. I appreciate any help in getting this to work.

   UITapGestureRecognizer *doubleTap =
    [[UITapGestureRecognizer alloc]
     initWithTarget:self
     action:@selector(tapDetected:)];
   [doubleTap setNumberOfTapsRequired : 1];
[doubleTap setDelaysTouchesBegan : YES];
    [self.view addGestureRecognizer:doubleTap];

Answer 1

You try this:-

UITapGestureRecognizer *singleTap = [[UITapGestureRecognizer alloc] initWithTarget: self action:@selector(tapDetected:)];
singleTap.numberOfTapsRequired = 1; 
[self.view addGestureRecognizer:singleTap];

UITapGestureRecognizer *doubleTap = [[UITapGestureRecognizer alloc] initWithTarget: self action:@selector(tapDetected:)];
doubleTap.numberOfTapsRequired = 2; 
[self.view addGestureRecognizer:doubleTap];

[singleTap requireGestureRecognizerToFail:doubleTap];

This works for me.

Answer 2

If You only want the receiver to respond to one/first touch then setDelaysTouchesBegan:NO Since this is used for processing touches in UITouchPhaseBegan so it is analyzed and is prevented from being delivered. Property discussion from documentation:

When the value of this property is NO (the default), views analyze touch events in UITouchPhaseBegan and UITouchPhaseMoved in parallel with the receiver. When the value of the property is YES, the window suspends delivery of touch objects in the UITouchPhaseBegan phase to the view. If the gesture recognizer subsequently recognizes its gesture, these touch objects are discarded. If the gesture recognizer, however, does not recognize its gesture, the window delivers these objects to the view in a touchesBegan:withEvent: message (and possibly a follow-up touchesMoved:withEvent: message to inform it of the touches' current locations). Set this property to YES to prevent views from processing any touches in the UITouchPhaseBegan phase that may be recognized as part of this gesture.

Answer 3

It looks to me like you are simply failing to set the delegate of your GestureRecognizer. Are you sure the double tap was firing successfully? When I placed your code into my project I see the same behavior but setting the delegate properly and using shouldRecognizeSimultaneouslyWithGestureRecognizer causes it to recognize the single tap properly.

UITapGestureRecognizer *doubleTap = [[UITapGestureRecognizer alloc] initWithTarget:self
                                                                            action:@selector(tapDetected:)];
[doubleTap setDelegate:self];
[doubleTap setNumberOfTapsRequired : 1];
[doubleTap setDelaysTouchesBegan : YES];
[picker addGestureRecognizer:doubleTap];

-(BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer
{
    if ([gestureRecognizer isKindOfClass:UITapGestureRecognizer.class] &&
        [otherGestureRecognizer isKindOfClass:UITapGestureRecognizer.class])
    {
        return YES;
    }
    else
    {
        return NO;
    }
}