How to listen to user touches for UICollectionViewCell in iOS?
You should implement UICollectionViewDelegate protocol method collectionView(_:didSelectItemAtIndexPath:). When you press one of your collection view cells this method get called. Here is sample implementation
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) { let url = thumbnailFileURLS[indexPath.item] if UIApplication.sharedApplication().canOpenURL(url) { UIApplication.sharedApplication().openURL(url) }}By the way I don't know where you get url. So I improvised a bit :)
Swift 5
didSelectItemAtIndexPath has been renamed to didSelectItemAt in Swift 5
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) { //Do your logic here }