UICollectionView drag finger over cells to select them

Question

Using UICollectionView, is it possible to select multiple cells by dragging your finger over a few of them? E.g., if you drag your finger over a row of 6, and d

Answer 1

You could use UIPanGestureRecognizer. And based on the location of the pan events, tracking what cells are passed through. When the gesture ends, you would have an array of selected cells.

Make sure that cancelsTouchesInView is set to NO. You'll need to set the delegate with gestureRecognizer:shouldRecognizeSimultaneouslyWithGestureRecognizer: and gestureRecognizerShouldBegin implemented to make sure the CollectionView can still scroll

Answer 2

Swift 3: Swipe to select with auto scrolling and working scroll.

var selectMode = false
var lastSelectedCell = IndexPath()

func setupCollectionView() {
    collectionView.canCancelContentTouches = false
    collectionView.allowsMultipleSelection = true
    let longpressGesture = UILongPressGestureRecognizer(target: self, action: #selector(didLongpress))
    longpressGesture.minimumPressDuration = 0.15
    longpressGesture.delaysTouchesBegan = true
    longpressGesture.delegate = self
    collectionView.addGestureRecognizer(longpressGesture)

    let panGesture = UIPanGestureRecognizer(target: self, action: #selector(didPan(toSelectCells:)))
    panGesture.delegate = self
    collectionView.addGestureRecognizer(panGesture)
}

func selectCell(_ indexPath: IndexPath, selected: Bool) {
    if let cell = collectionView.cellForItem(at: indexPath) {
        if cell.isSelected {
            collectionView.deselectItem(at: indexPath, animated: true)
            collectionView.scrollToItem(at: indexPath, at: UICollectionViewScrollPosition.centeredVertically, animated: true)
        } else {
            collectionView.selectItem(at: indexPath, animated: true, scrollPosition: UICollectionViewScrollPosition.centeredVertically)
        }
        if let numberOfSelections = collectionView.indexPathsForSelectedItems?.count {
            title = "\(numberOfSelections) items selected"
        }
    }
}

func didPan(toSelectCells panGesture: UIPanGestureRecognizer) {
    if !selectMode {
        collectionView?.isScrollEnabled = true
        return
    } else {
        if panGesture.state == .began {
            collectionView?.isUserInteractionEnabled = false
            collectionView?.isScrollEnabled = false
        }
        else if panGesture.state == .changed {
            let location: CGPoint = panGesture.location(in: collectionView)
            if let indexPath: IndexPath = collectionView?.indexPathForItem(at: location) {
                if indexPath != lastSelectedCell {
                    self.selectCell(indexPath, selected: true)
                    lastSelectedCell = indexPath
                }
            }
        } else if panGesture.state == .ended {
            collectionView?.isScrollEnabled = true
            collectionView?.isUserInteractionEnabled = true
            swipeSelect = false
        }
    }
}

func didLongpress() {
    swipeSelect = true
}