How to detect double-taps on cells in a UICollectionView

Question

I want to respond to double-taps on cells in a UICollectionView, and have a double-tap action cancel cell selection.

This is what I've tried:

UITapGestureRecognizer *tapRecogniser = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(handleTapGesture:)];
tapRecogniser.numberOfTapsRequired = 2;

 for (UITapGestureRecognizer *recogniser in [self.collectionView gestureRecognizers]) {
    [recogniser requireGestureRecognizerToFail:tapRecogniser];
}

[self.collectionView addGestureRecognizer:tapRecogniser];

That is, I am trying to get the default gesture recognisers to fail if my double-tap gesture recogniser succeeds.

This doesn't appear to work, as my collection view delegate's collectionView:didSelectItemAtIndexPath: is still getting called after a double-tap

---

Note on Apple's UICollectionViewController Docs

Apple's documentation is misleading on this point, claiming that the default gesture recogniser is an instance of a UITapGestureRecognizer subclass, so it can be easily picked out with [recogniser isKindOfClass:[UITapGestureRecognizer class]]. Unfortunately this is an error.

Answer 1

I don't see why you need the requireToFail. I use double-taps in a UICollectionView and it doesn't interfere with my single taps (used for selection).

I use the following:

UITapGestureRecognizer *doubleTapFolderGesture = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(processDoubleTap:)];
[doubleTapFolderGesture setNumberOfTapsRequired:2];
[doubleTapFolderGesture setNumberOfTouchesRequired:1];
[self.view addGestureRecognizer:doubleTapFolderGesture];

Then, this:

- (void) processDoubleTap:(UITapGestureRecognizer *)sender
{
    if (sender.state == UIGestureRecognizerStateEnded)
    {
        CGPoint point = [sender locationInView:collectionView];
        NSIndexPath *indexPath = [collectionView indexPathForItemAtPoint:point];
        if (indexPath)
        {
            NSLog(@"Image was double tapped");
        }
        else 
        {
            DoSomeOtherStuffHereThatIsntRelated;
        }
    }
}

Seems to working fine -- the double tap is recognized and I can handle it as I wish (in this case I'm expanding the contents of a folder). But a single-tap will cause the tapped sell to be selected, which I haven't written any gesture recognition for.

IMPORTANT EDIT:

I am revisiting this question because I've seen that my original answer can be wrong in certain circumstances, and there is an apparent fix that seems to work.

The following line needs to be added:

doubleTapFolderGesture.delaysTouchesBegan = YES;

which eliminates interference with the single tap for cell selection. This provides a much more robust setup.