Tapping cell in UICollectionView returns wrong index - ios

Question

I really don't know what I am missing. I've got a UICollectionView set up and the contents are set correctly. The cellForItemAt section looks like this:
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "DetailsEventImageCell", for: indexPath) as? DetailsEventImageCell
print("Loaded - IndexPathItem: \(indexPath.item)")
cell?.backgroundColor = .clear
cell?.contentView.layer.cornerRadius = 10
cell?.contentView.layer.masksToBounds = true
cell?.eventImage.image = images[indexPath.row]
return cell ?? UICollectionViewCell()
}
The collectionView shows the cells correctly but here's the problem. When I go into editing Mode and tap through all the cells randomly, sometimes it returns the wrong index and marks the wrong cell (mostly right next to it) as shown in the image below:
The cell I tap should return indexPath.item = 5 but it does return 4 and marks cell 4 for deletion instead of 5.
As the cells are set up correctly I don't know why it occasionally returns the wrong indexPath for the selected cell. If I tap on a cell twice it suddenly returns the correct indexPath. If I deselect all cells and try again, there some cells return the wrong indexPath again.
Here's my didSelectItemAt Code
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
print(indexPath.item)
if isEditing {
if let cell = collectionView.cellForItem(at: indexPath) as? DetailsEventImageCell {
cell.isInEditingMode = isEditing
cell.isSelected = true
}
}
}
The following two functions might also be the culprit, but I just don't see why it would set up the collectionView correctly and then on tapping return the wrong value.
This is my custom cell:
class DetailsEventImageCell: UICollectionViewCell {
#IBOutlet weak var eventImage: UIImageView!
#IBOutlet weak var selectedForDeletionImage: UIImageView!
var isInEditingMode: Bool = false {
didSet {
if !isInEditingMode {
//selectedForDeletionImage.isHidden = true
isSelected = false
}
}
}
override var isSelected: Bool {
didSet {
if isInEditingMode {
selectedForDeletionImage.isHidden = isSelected ? false : true
}
}
}
And this is my setEditing code
override func setEditing(_ editing: Bool, animated: Bool) {
super.setEditing(editing, animated: animated)
collectionView.allowsMultipleSelection = editing
//Deselect all selected cells
if !editing {
if let indexPaths = collectionView.indexPathsForSelectedItems {
for indexPath in indexPaths {
self.collectionView.deselectItem(at: indexPath, animated: false)
}
}
}
let indexPaths = collectionView.indexPathsForVisibleItems
for indexPath in indexPaths {
if let cell = collectionView.cellForItem(at: indexPath) as? DetailsEventImageCell {
cell.isInEditingMode = editing
}
}
}
I hope someone can help me with this.

Answer 1

I think the above implementation won't work if u have many cells because cells are reusable.
you can collect selected Indexpaths in Array, reload on every didSelece/didDeselect method.
Do the UI updates in cellforRowAtItem method.
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
if isEditing {
self.selectedIndexPaths.append(indexPath)
self.collectionView.reloadData()
}
}
In didDeselect method will be like...
func collectionView(_ collectionView: UICollectionView, didDeselectItemAt indexPath: IndexPath) {
if let index = self.selectedIndexPaths.firstIndex(of: indexPath) {
self.selectedIndexPaths.remove(at: index)
}
self.collectionView.reloadData()
}
finally cellforRowAtItem will be like...
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "DetailsEventImageCell", for: indexPath) as? DetailsEventImageCell
print("Loaded - IndexPathItem: \(indexPath.item)")
cell?.backgroundColor = .clear
cell?.contentView.layer.cornerRadius = 10
cell?.contentView.layer.masksToBounds = true
cell?.eventImage.image = images[indexPath.row]
if self.selectedIndexpaths.contains(indexPath) {
cell.isSelected = true
} else {
cell.isSelected = false
}
return cell ?? UICollectionViewCell()
}

Answer 2

After hours of trying I found out that this seems to be an iOS Simulator related issue. I don't have access to all device sizes, so I sometimes do use it for quick testing.
Tapping cells "slowly" in the simulator does work as expected, but if I tap inside cells too fast it seems like it's not keeping up and selecting the previous cell again.
On an actual device it's possible to tap on cells at any speed and it works as intended.
Edit: The problem seems to only appear on the iOS-Simulator on my Mac Mini late 2012 (macOS Catalina 10.15.6) on XCode 11.7
My Macbook Pro 15" 2019 and all hardware devices I tried (iPhone 11 Pro, ipad Air, iPhone SE 2nd Gen) do work as expected with the same project and the same OS/XCode Build.