UIGestureRecognizerStateBegan calling twice in iOS 6

Question

Giving thanks in advance, I would like to share the strange behaviour of UILongPressGestureRecognizer.

UIView *v = [UIView alloc] initWithFrame:CGRectMake(0,0,20,20)];
UILongPressGestureRecognizer *longpressGesture1 = [[UILongPressGestureRecognizer alloc] initWithTarget:self action:@selector(tapped:)];
[v addGestureRecognizer:longpressGesture1];

and here the delegate to handle the gesture recogniser.

-(IBAction)tapped:(UILongPressGestureRecognizer *) gesture

{ 
    switch ([gesture state]) {
        case UIGestureRecognizerStateBegan:
        {

            NSLog(@"Long Tap detacted.");  

        }
            break;
        case UIGestureRecognizerStateChanged:
        {
            NSLog(@"UIGestureRecognizerStateChanged");


        }
            break;
        case UIGestureRecognizerStateEnded:
        {
            NSLog(@"Long Tap ended.");

        }
            break;

    }

}

This piece of code is working perfectly as expected in iOS 4 and 5, but in ios 6 with retina display when we perform the long tap, UIGestureRecognizerStateBegan is being called twice for a single long tap resulting in a application crash. Any help is greatly welcome.

Please see http://stackoverflow.com/a/3320351/792677 Feel free to provide and accept an answer with the fixed code. — A-Live, Mar 12 '13 at 14:09

Rajneesh071 · Answer 1 · 2013-03-12T14:25:40.223

2

UILongPressGestureRecognizer is a continuous event recognizer. You have to look at the state to see if this is the start, middle or end of the event and act accordingly.

Its calling two times because you are pressing and removing your finger.

First call is indicating you that there is an Long tap detected i.e. UIGestureRecognizerStateBegan Second call is indicating you that there is end of that tap i.e. UIGestureRecognizerStateBegan

There are three state of tap

UIGestureRecognizerStateBegan
UIGestureRecognizerStateChanged
UIGestureRecognizerStateEnded

If you will drag your finger then it will called multiple time that will indicate that there is some changes in its state.

Follow UILongPressGestureRecognizer Class Reference for more

edited Mar 12 '13 at 14:25

answered Mar 12 '13 at 14:15

Rajneesh071

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No, I am not pressing and removing the fingers. It happens on a same event i.e pressing. That's why it working on iOS4 and ios5 but not in ios6 – Rajan Twanabashu Mar 12 '13 at 14:18
when you are pressing finger then its indicating that an event is happening and after finishing your long press its indicating end of tap – Rajneesh071 Mar 12 '13 at 14:28
I haven't reached finishing tap. I am still holding long tap. – Rajan Twanabashu Mar 13 '13 at 05:40
i tried your code with iOS 6 and output in nslog is Long Tap detacted. and Long Tap ended. – Rajneesh071 Mar 13 '13 at 08:05
Thanks for your response. I too expected the same in all the version of ios. But i failed to received it in iOS 6 with retina display. – Rajan Twanabashu Mar 13 '13 at 08:51

UIGestureRecognizerStateBegan calling twice in iOS 6

1 Answers1