每节iOS UICollectionView单元格选择

Question

I was wondering how to set up my UICollectionView so that up to 1 cell can be selected per section. I see that there is the allowsMultipleSelection property for UICollectionView but I'm wondering how to prevent multiple cells from being selected in the same section.

Do I need to implement logic in the – collectionView:shouldSelectItemAtIndexPath: and collectionView:shouldDeselectItemAtIndexPath: methods or is there a simpler way?

Thanks!

Answer 1

In your didSelectRowAtIndexPath you could do something like this:

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
    NSArray * selectedRows = self.tableView.indexPathsForSelectedRows;

    for (NSIndexPath * selectedRow in selectedRows) {
        if ((selectedRow.section == indexPath.section) && (selectedRow.row != indexPath.row)) {
            [self.tableView deselectRowAtIndexPath:selectedRow animated:NO];
        }
    }
}

allowsMultipleSelection should be set to YES.

Hope it helps!

Answer 2

In Swift 2.0 :

override func viewDidLoad() {
    super.viewDidLoad()

    self.collectionView.allowsMultipleSelection = true
}

func collectionView(collectionView: UICollectionView, didSelectItemAtIndexPath indexPath: NSIndexPath) {

    let selectedRows: [NSIndexPath] = self.collectionView.indexPathsForSelectedItems()!
    for selectedRow: NSIndexPath in selectedRows {
        if (selectedRow.section == indexPath.section) && (selectedRow.row != indexPath.row) {
            self.collectionView.deselectItemAtIndexPath(selectedRow, animated: false)
        }
    }
}

Answer 3

You'll probably need to do logic in -shouldSelect and -shouldDeselect . Maybe keep a dictionary of number of cells selected per section ?

NSMutableDictionary *dict;

- (BOOL)collectionView:(UICollectionView *)view shouldSelectItemAtIndexPath:(NSIndexPath *)path
{
    NSInteger *section = path.section;
    if (!dict)
    {
        dict = [[NSMutableDictionary alloc] init];
    }
    NSNumber *numberSelected = [dict objectForKey:[NSNumber numberWithInteger:section]];
    if (numberSelected > 0)
    {
        return NO;
    }
    else
    {
        [dict setObject:[NSNumber numberWithDouble:numberSelected.doubleValue - 1] forKey:[NSNumber numberWithInteger:section]];
        return YES;
    }
}
- (BOOL)collectionView:(UICollectionView *)view shouldDeselectItemAtIndexPath:(NSIndexPath *)path
{
    NSInteger *section = path.section;
    if (!dict)
    {
        dict = [[NSMutableDictionary alloc] init];
    }
    NSNumber *numberSelected = [dict objectForKey:[NSNumber numberWithInteger:section]];

    numberSelected = [NSNumber numberWithDouble:numberSelected.doubleValue - 1];

    [dict setObject:numberSelected forKey:[NSNumber numberWithInteger:section]];

    return YES;
}

That should work.

Answer 4

In Swift 5.0:

override func viewDidLoad() {
    super.viewDidLoad()
    self.collectionView.allowsMultipleSelection = true
}

func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
    (collectionView.indexPathsForSelectedItems ?? [])
        .filter { $0.section == indexPath.section && $0.item != indexPath.item && $0.row != indexPath.row }
        .forEach { self.collectionView.deselectItem(at: $0, animated: false) }
}

if you want it to toggle between items in section use this:

override func viewDidLoad() {
    super.viewDidLoad()
    self.collectionView.allowsMultipleSelection = true
}

func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
    (collectionView.indexPathsForSelectedItems ?? [])
        .filter { $0.section == indexPath.section && $0.item }
        .forEach { self.collectionView.deselectItem(at: $0, animated: false) }
}

I think that makes better user experience but it's your call