uicollectionview select an item immediately after reloaddata?

Question

After calling -[UICollectionView reloadData] it takes some time for cells to be displayed, so selecting an item immediately after calling reloadData does not work. Is there a way to select an item immediately after reloadData?

Answer 1

Along the lines of this answer I found that calling layoutIfNeeded after reloadData seemed to effectively 'flush' the reload before I do other things to the collectionView:

[self.collectionView reloadData];
[self.collectionView layoutIfNeeded];
...

On the page I found this solution, some commenters indicated it didn't work for them on iOS 9, but it's been fine for me so your mileage may vary.

Answer 2

The Swift way:

let selected = collectionView.indexPathsForSelectedItems()
collectionView.performBatchUpdates({ [weak self] in
    self?.collectionView.reloadSections(NSIndexSet(index: 0))
    }) { completed -> Void in
        selected?.forEach { [weak self] indexPath in
            self?.collectionView.selectItemAtIndexPath(indexPath, animated: false, scrollPosition: [])
        }
}

Answer 3

I'm handling selection of cells in collectionView: cellForItemAtIndexPath:. The problem I found was that if the cell didn't exist, simply calling selectItemAtIndexPath: animated: scrollPosition: wouldn't actually select the item.

Instead you have to do:

cell.selected = YES;
[m_collectionView selectItemAtIndexPath:indexPath animated:NO scrollPosition:UICollectionViewScrollPositionNone];