Animation Glitch When Deleting UICollectionViewDiffableDataSource Item From Context Menu - ios

Question

I have adopted the new UICollectionViewDiffableDataSource. I am applying a datasource snapshot everytime I delete an item:
var snapshot = NSDiffableDataSourceSnapshot<Int, Item>()
snapshot.appendSections([0])
snapshot.appendItems(items)
apply(snapshot, animatingDifferences: true)
The delete is offered through the built in collection view configuration option:
func collectionView(_ collectionView: UICollectionView, contextMenuConfigurationForItemAt indexPath: IndexPath, point: CGPoint) -> UIContextMenuConfiguration? {
guard let item = dataSource.itemIdentifier(for: indexPath) else {
return nil
}
let configuration = UIContextMenuConfiguration(identifier: nil, previewProvider: nil) { _ in
let delete = UIAction(title: "Delete", image: UIImage(systemName: "trash.fill"), attributes: .destructive) { _ in
self.deleteItem(item)
}
return UIMenu(title: "", image: nil, identifier: nil, children: [delete])
}
return configuration
}
If I delete the item from outside the context menu, the animation works great. If I delete from the context menu then one cell disappears and then causes the next to flash. I suspect there is some sort of conflict between closing the context menu & running the delete animation. I'm looking for a way to work around this.

Answer 1

edit: This was very stable resulting in freezing of the UI and other weird glitches where it sometimes didn't respond to long-press, do not use this. I wish this API didn't have that glitch, it's very annoying.
I found this ugly glitch too and was very close on giving up until I thought I'd give it a shot implementing the other interaction API instead of the built-in on UICollectionView, weirdly enough the animation went away.
First add the interaction to your cells contentView
let interaction = UIContextMenuInteraction(delegate: self)
cell.contentView.addInteraction(interaction)
Then implement the delegate, presumably where you present the cell, in my case in the viewController
extension ViewController : UIContextMenuInteractionDelegate {
func contextMenuInteraction(_ interaction: UIContextMenuInteraction, configurationForMenuAtLocation location: CGPoint) -> UIContextMenuConfiguration? {
// loop through all visible cells to find which one we interacted with
guard let cell = collectionView.visibleCells.first(where: { $0.contentView == interaction.view }) else {
return nil
}
// convert it to an indexPath
guard let indexPath = collectionView.indexPath(for: cell) else {
return nil
}
// continue with your magic!
}
}
And voila, that's it, no more glitchy animation.
I don't know if there's some edge cases where wrong cell will be selected or other weird stuff, but this seems to work just fine.