How to determine when a custom UICollectionViewCell is 100% on the screen

Question

From the diagram above I have UICollectionView with 4 custom cells. At any time 2 or three cells can be on the screen. How can I tell when \"cell 1\"

Answer 1

You can filter your visibleCells array to check if the frame of your cell is included in the frame of your collectionView:

    var visibleCells = self.collectionView?.visibleCells
    visibleCells = visibleCells?.filter({ cell -> Bool in
        return self.collectionView?.frame.contains(cell.frame) ?? false
    })
    print (visibleCells)