How to detect double-taps on cells in a UICollecti

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

There are a bunch of good solutions here but unfortunately they didn't work reliably for me (e.g. I could not get the double tap to trigger consistently possibly because I was also implemented didSelectItemAtIndexPath).

What worked for me was adding the (double)tap gesture recognizer to the collection view instead of the cell. In its action selector I would determine which cell was double tapped and do whatever I needed to do. Hopefully this helps someone:

- (void)viewDidLoad
{
    UITapGestureRecognizer *doubleTapGesture = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(didDoubleTapCollectionView:)];
    doubleTapGesture.numberOfTapsRequired = 2;
    [self.collectionView addGestureRecognizer:doubleTapGesture];
}

- (void)didDoubleTapCollectionView:(UITapGestureRecognizer *)gesture {

    CGPoint pointInCollectionView = [gesture locationInView:self.collectionView];
    NSIndexPath *selectedIndexPath = [self.collectionView indexPathForItemAtPoint:pointInCollectionView];
    UICollectionViewCell *selectedCell = [self.collectionView cellForItemAtIndexPath:selectedIndexPath];

    // do something
}

Answer 2

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.

Answer 3

The requireGestureRecognizerToFail: called on the default gesture recognisers does actually work (that is, their state goes to UIGestureRecognizerStateFailed if a double-tap is recognized).

But it seems UICollectionView's collectionView:didSelectItemAtIndexPath: delegate callback doesn't take account of this, ie. it's still called when the default gesture recogniser fails.

So the answer/workaround is to make sure the delegate's collectionView:shouldSelectItemAtIndexPath: and collectionView:shouldDeselectItemAtIndexPath: implementations check the state of (one of?) the default gesture recognisers, thus:

- (BOOL)collectionView:(UICollectionView *)collectionView shouldSelectItemAtIndexPath:(NSIndexPath *)indexPath {

    UITapGestureRecognizer *defaultGestureRecogniser = [[self.collectionView gestureRecognizers] objectAtIndex:0];
    return defaultGestureRecogniser.state != UIGestureRecognizerStateFailed;
}

Answer 4

My solution was to not implement collectionView:didSelectItemAtIndexPath but to implement two gesture recognizers.

    self.doubleTapGesture = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(processDoubleTap:)];
    [_doubleTapGesture setNumberOfTapsRequired:2];
    [_doubleTapGesture setNumberOfTouchesRequired:1];   

    [self.view addGestureRecognizer:_doubleTapGesture];

    self.singleTapGesture = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(processSingleTap:)];
    [_singleTapGesture setNumberOfTapsRequired:1];
    [_singleTapGesture setNumberOfTouchesRequired:1];
    [_singleTapGesture requireGestureRecognizerToFail:_doubleTapGesture];

    [self.view addGestureRecognizer:_singleTapGesture];

This way I can handle single and double taps. The only gotcha I can see is that the cell is selected on doubleTaps but if this bothers you can you handle it in your two selectors.