Add functionality to standard Pan Gesture Recognizer in a UIScrollView

Question

I am trying to keep track of where a finger is in a UIScrollView. I have subclassed UIScrollView (see below) but unfortunately the gesture recognizer that I am adding is overriding the standard one.

As a result I get NSLog(@"Pan") to work but unfortunately the view doesn't scroll anymore.

How can I get both gestures recognizers to work at the same time?

Thanks.

- (void)viewDidLoad:(BOOL)animated
{
    [super viewDidLoad:animated];

    UIPanGestureRecognizer *panRecognizer = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(pan:)];
    [scrollView addGestureRecognizer:panRecognizer];
}


- (void)pan:(id)sender {
    NSLog(@"Pan");
}

You don't say what you expect to happen when both things happen at the same time. Do you expect it to scroll *and* update your pan recognizer? If so, why not just listen to the scroll view delegate methods that get called when the view is scrolled? — Ben Zotto, Dec 04 '11 at 18:26
I'd like the view to both scroll and record all the points touched (that I know I can retrieve through the `locationInView:` method). The scroll view delegate sounds interesting -I've never heard of that... I am quite new to iOS programming-, how would that work? Thanks. — ios-lizard, Dec 04 '11 at 19:13
I have found [this reference on scroll view delegates](http://developer.apple.com/library/ios/#documentation/UIKit/Reference/UIScrollViewDelegate_Protocol/Reference/UIScrollViewDelegate.html#//apple_ref/occ/intf/UIScrollViewDelegate) but I do not understand how to retrieve the coordinates of the touch. — ios-lizard, Dec 04 '11 at 23:46

score 14 · Answer 1 · answered Mar 29 '12 at 13:51

If you want it not to override the standard one you just have to allow both to be simultaneously recognized.

- (void)viewDidLoad:(BOOL)animated
{
    [super viewDidLoad:animated];

    UIPanGestureRecognizer *panRecognizer = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(pan:)];
    panRecognizer.delegate = self;
    [scrollView addGestureRecognizer:panRecognizer];
}

- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer
{
     return TRUE;
}


- (void)pan:(id)sender {
    NSLog(@"Pan");
}

score 4 · Accepted Answer · edited May 23 '17 at 12:17

EDIT: this method works! You just need to set canCancelContentTouches as soon as possible (I do it in viewDidLoad).

ORIGINAL ANSWER: I have tried a new approach but unfortunately it doesn't fully work.

Instead of adding a gesture recognizer I am subclassing the UIScrollView and writing my own touchesBegan, touchesMoved, etc methods.

This way I know where the user is touching BUT unfortunately the PanGestureRecognizer is triggering touchesCancelled every time I start to scroll even after setting the canCancelContentTouches to NO.

Does anybody know why? I have also found this.

Add functionality to standard Pan Gesture Recognizer in a UIScrollView

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