UIGestureRecognizerStateBegan calling twice in iOS 6 - iphone

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.

Answer 1

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