PAN Gesture is crashing while taking the location of touch in view in iOS

Question

I just do a sample to check the pan gesture.

The pan gesture is detecting and working fine.

But whenever i give a secondPoint in the pan gesture like CGPoint secondPoint = [sender locationOfTouch:1 inView:self.imageView]; it is crashing.

The console is giving the message

 *** Terminating app due to uncaught exception 'NSRangeException', reason: '-[UIPanGestureRecognizer locationOfTouch:inView:]: index (1) beyond bounds (1).'

When I use panGestureRecognizer.maximumNumberOfTouches = 1; panGestureRecognizer.minimumNumberOfTouches =1; still it is crashing.

When I use panGestureRecognizer.maximumNumberOfTouches = 2; panGestureRecognizer.minimumNumberOfTouches = 2; then it is not entering into the

- (void)panGestureHandler:(UIPanGestureRecognizer *)sender method.

Can anyone please guide me where im going wrong.

Thanks in advance.Hoping for your help.

I tried in this way.

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.

    UIPanGestureRecognizer *panGestureRecognizer = [[UIPanGestureRecognizer alloc]initWithTarget:self action:@selector(panGestureHandler:)];
     panGestureRecognizer.maximumNumberOfTouches = 2;
     [self.imageView addGestureRecognizer:panGestureRecognizer];

}
- (void)panGestureHandler:(UIPanGestureRecognizer *)sender
{
    if ([sender state] == UIGestureRecognizerStateBegan )
    {
        CGPoint firstPoint = [sender locationOfTouch:0 inView:self.imageView];
        CGPoint secondPoint = [sender locationOfTouch:1 inView:self.imageView];
    }
    else if ([sender state] ==UIGestureRecognizerStateEnded ) 
    {
    }

}

Answer 1

I too came across this error despite the max and min number of touches being set. I'm subclassing my gesture recognizer and figure it has something to do with that. I got around it by simply checking numberOfTouches before referencing it:

if ([gestureRecognizer numberOfTouches] > 0) {
    CGPoint point = [gestureRecognizer locationOfTouch:0 inView:self.superview.window];
}

Hope this helps someone!

Answer 2

You provided a maximumNumberOfTouches, but no minimumNumberOfTouches. I.e., the gesture can be recognized after the first touch. In this case, no second touch may exist, and your index 1 (referring the second element) exceeds the array bounds.