UICollectionView：将一个单元格拖动/移动到另一个单元格（无重新排序）

Question

In swift I would like to drag one cell inside the UICollectionView onto another cell. I found several, good tutorials for reordering, but I would like to move only the touched element, other cells shall keep their positions. Behavior would be same as on home screen to create folders by dragging one item onto another.

Already setup view controller with UICollectionView and following events:

func collectionNode(_ collectionNode: ASCollectionNode, canMoveItemWith node: ASCellNode) -> Bool {}

func collectionNode(_ collectionNode: ASCollectionNode, moveItemAt sourceIndexPath: IndexPath, to destinationIndexPath: IndexPath) {}

@objc func handleLongGesture(gesture: UILongPressGestureRecognizer) {}

Finally figured out:

self.collectionView.view.updateInteractiveMovementTargetPosition(gesture.location(in: gesture.view!))

will update the view with reordering the items. Is there any alternative/option to keep the position of the other items?

Answer 1

Okay, using wrong API functions. If you have a similar problem, please follow the tutorial of Ray: https://www.raywenderlich.com/3121851-drag-and-drop-tutorial-for-ios

This is quite self explaining although it has its complexity.

Bottom line: the above discussed API functions only provide re-ordering of items, to put items onto each other, this is a drag'n drop instead, requiring nothing more than implementing three functions:

func collectionView(_ collectionView: UICollectionView, itemsForBeginning session: UIDragSession, at indexPath: IndexPath) -> [UIDragItem] {}

func collectionView(_ collectionView: UICollectionView, performDropWith coordinator: UICollectionViewDropCoordinator) {}

func collectionView(_ collectionView: UICollectionView, dropSessionDidUpdate session: UIDropSession, withDestinationIndexPath destinationIndexPath: IndexPath?) -> UICollectionViewDropProposal {}

Make sure to use UICollectionViewDropProposal(operation: .move, intent: .insertIntoDestinationIndexPath) in the last function as return to allow moving above an object, otherwise Swift UI will again change position of existing items.

Furthermore, make sure to enable dragging: view.dragInteractionEnabled = true

view is then your collection view.