UICollectionView - random cells are selected

Question

I have a Horizontal UICollectionView like the horizontal Calender in iOS. Paging is enabled but not allowsMultipleSelection.

self.allowsMultipleSelection = fals         


        

Answer 1

First, if you want to preserve multiple selection, you have to remember your selected ones in an array since it would get lost if a cell gets recycled and reused. For that use something like a [IndexPath] type). If one selected cell is enough, you could use a non-array version of below code.

var selectedItems: [IndexPath] = []

Then, do your recoloring in your cell's cellForItemAt(:):

cell.backgroundColor = selectedItems.contains(indexPath) ? .red : .white

Your didSelectItemAt delegate function should look like:

if !selectedItems.contains(indexPath) { selectedItems.append(indexPath)}

collectionView.cellForItem(at: indexPath)?.backgroundColor = .red

and your didDeselectItemAt delegate function:

if let index = selectedItems.firstIndex(of: indexPath) { selectedItems.remove(at: index) }

collectionView.cellForItem(at: indexPath)?.backgroundColor = .white

This should actually work. Let me know if we have to do adjustments.

Answer 2

Take a class-level variable, say index

var index = -1

As you have said that multiple selections are not allowed so the following will do the job for you

func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
    index = indexPath.item
    collectionView.reloadData()
}

func collectionView(_ collectionView: UICollectionView, didDeselectItemAt indexPath: IndexPath) {
    let cell = collectionView.cellForItem(at: indexPath)
    if let cell = cell {
        cell.backgroundColor = indexPath.item == index ? .red :  .white
    }
}

Whenever user tap on any cell we save the position in index variable and then call the reloadData() to notify collectionView about the change In cellForRowAt we check if the current cell us selected we set the color to red otherwise white

Answer 3

Don't forget that UICollectionView has embedded reusing mechanism, so you should deselect your cells in the method "prepareToReuse" directly inside the cell class.