问题

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?

回答1:

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.

回答2:

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")
    }
}

来源：https://stackoverflow.com/questions/40365971/how-to-add-tap-gesture-to-uicollectionview-while-maintaining-cell-selection

标签

ios