UICollectionView, how to prevent one cell from being moved

Question

I recently study collection view. I need to let some cells fix in their own index path, which mean they should not be exchanged by others and not be dragged. I now can use *- (BOOL)collectionView:(UICollectionView *)collectionView canMoveItemAtIndexPath:(NSIndexPath )indexPath to prevent them from dragging. I cannot prevent them from being exchanged by other cells.

Any one meet same issue?

Thanks

Answer 1

func collectionView(_ collectionView: UICollectionView, targetIndexPathForMoveFromItemAt originalIndexPath: IndexPath, toProposedIndexPath proposedIndexPath: IndexPath) -> IndexPath {
    if proposedIndexPath.row == data.count {
        return IndexPath(row: proposedIndexPath.row - 1, section: proposedIndexPath.section)
    } else {
        return proposedIndexPath
    }
}

Answer 2

I found that when I used iOS 11+ drag and drop, targetIndexPathForMoveFromItemAt wouldn't get called. Implementing this method forbids the item from being dropped where I don't want it:

func collectionView(_ collectionView: UICollectionView, dropSessionDidUpdate session: UIDropSession, withDestinationIndexPath destinationIndexPath: IndexPath?) -> UICollectionViewDropProposal {
    // disallow dragging across sections
    guard let sourcePath = session.items.first?.localObject as? IndexPath,
        let destPath = destinationIndexPath,
        sourcePath.section == destPath.section
        else {
            return UICollectionViewDropProposal(operation: .forbidden)
    }
    return UICollectionViewDropProposal(operation: .move, intent: .insertAtDestinationIndexPath)
}

Note that I stored the source index path in localObject when the drag started, because I couldn't find a way to get this information otherwise.