CODEWITHSUNDEEP
iosswiftuicollectionview
Cheok Yan Cheng
Cheok Yan Cheng

Reputation: 42710

During drag-n-reorder operation, how to detect when the cell is visually being switched position?

I use the following code snippet to implement drag and reorder operation.

class DashboardViewController {
    private func initCollectionView() {
        ...
        
        let gesture = UILongPressGestureRecognizer(target: self, action: #selector(longPressGesture))
        collectionView.addGestureRecognizer(gesture)
    }
    
    @objc func longPressGesture(_ gesture: UILongPressGestureRecognizer) {
        switch gesture.state {
        case .began:
            self.began(gesture)
        case .changed:
            self.changed(gesture)
        case .ended:
            self.ended(gesture)
        default:
            self.cancel(gesture)
        }
    }
}

extension DashboardViewController {
    func began(_ gesture: UILongPressGestureRecognizer) {
        print(">> began")
        
        let location = gesture.location(in: self.collectionView)
        
        guard let indexPath = self.collectionView.indexPathForItem(at: location) else {
            return
        }
        
        collectionView.beginInteractiveMovementForItem(at: indexPath)
    }
    
    func changed(_ gesture: UILongPressGestureRecognizer) {
        print(">> changed")
        
        collectionView.updateInteractiveMovementTargetPosition(location)
    }
    
    func ended(_ gesture: UILongPressGestureRecognizer) {
        print(">> ended")
        
        collectionView.endInteractiveMovement()
    }
    
    func cancel(_ gesture: UILongPressGestureRecognizer) {
        print(">> cancel")

        collectionView.endInteractiveMovement()
    }
}

enter image description here

As you can see in the screenshot, when I start to drag and 1st cell, changed will keep being called.

When I drag close enough to the 2nd cell, the 2nd cell will then visually switch position to 1st.

I would like to be able to detect, when the 2nd cell is visually switch position to the 1st. Does anyone know how I can achieve so?

Thanks.

Upvotes: 3

Views: 386

Answers (1)

Prashant Tukadiya
Prashant Tukadiya

Reputation: 16446

You may not able to find the visually cell is switched to the 1st position but you may try to check after some delay when switching is happening

you will get this delegate method called when you drag the cell

optional func collectionView(_ collectionView: UICollectionView, 
       targetIndexPathForMoveOfItemFromOriginalIndexPath originalIndexPath: IndexPath, 
      atCurrentIndexPath currentIndexPath: IndexPath, 
     toProposedIndexPath proposedIndexPath: IndexPath) -> IndexPath

here is the doc url

https://developer.apple.com/documentation/uikit/uicollectionviewdelegate/3750828-collectionview

Upvotes: 2

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