How to add tap gesture to UICollectionView , while maintaining cell selection?

Question

Task

Add a single tap gesture to UICollectionView, do not get in the way of cell selection.

I want some other taps on the no-cell part of the collectionView.

Code

Using XCode8, Swift 3.

override func viewDidLoad() {
    ...
    collectionView.addGestureRecognizer(UITapGestureRecognizer(target: self, action: #selector(tap)))
}

func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
    print(indexPath)
}

func tap(sender: UITapGestureRecognizer){
    print("tapped")
}

Result

Yeah, it gets in the way now. When you tap on cell, it logs "tapped".

Analysis

I check the hitTest return value of the collectionView and the cell. Both returned the tapped cell, which means they form a responder chain of Cell -> CollectionView
no gestures on the cell
3 gestures on collectionView, no one seems to work with the cell select
- UIScrollViewDelayedTouchesBeganGestureRecognizer
- UIScrollViewPanGestureRecognizer
- UITapGestureRecognizer
callStack, seems cell selection has a different stack trace with gesture's target-action pattern.
double tap gesture works along with cell selection.

Question

Couldn't find more trace. Any ideas on how cell selection is implemented or to achieve this task?

score 44 · Accepted Answer · edited Jan 30 '17 at 16:01

44

Whenever you want to add a gesture recognizer, but not steal the touches from the target view, you should set UIGestureRecognizer.cancelsTouchesInView for your gestureRecognizer instance to false.

edited Jan 30 '17 at 16:01

Yi Jiang

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answered Nov 01 '16 at 18:54

Josh Homann

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Thanks! I returned to the basic docs again and try to find anything I miss! – addlistener Nov 03 '16 at 08:23

score 17 · Answer 2 · answered Nov 01 '16 at 18:43

17

Instead of trying to force didSelectItem you can just get the indexPath and/or cell this way:

func tap(sender: UITapGestureRecognizer){

    if let indexPath = self.collectionView?.indexPathForItem(at: sender.location(in: self.collectionView)) {
        let cell = self.collectionView?.cellForItem(at: indexPath)
        print("you can do something with the cell or index path here")
    } else {
        print("collection view was tapped")
    }
}

answered Nov 01 '16 at 18:43

Frankie

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Thanks! This is really helpful. I'm going to add more gestures to the collectionView. Seems like UICollectionView is analysing raw touches rather than using a high level gesture recogniser, and that's limited. – addlistener Nov 03 '16 at 08:25

score 0 · Answer 3 · answered May 25 '22 at 10:02

I get another way: when adding gestures, set delegate, implement below method

- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldReceiveTouch:(UITouch *)touch

you can decide whether the gesture recognizer to receive the touch by your own logic, with position or the page's hidden property, based on your demand.