iOS collectionView: how to scroll a cell to the top of the screen

Question

I am wondering if there is a way to scroll a certain UICollectionViewCell to the top of the view? I tried the collectionView.scrollToItemAtIndexPath() method, but instead of scrolling the cell to the top of the view, it scroll the cell to the center of the view.

Answer 1

You may use below code:

#pragma mark - UICollectionViewDelegate

- (void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath
{
    [collectionView scrollToItemAtIndexPath:indexPath atScrollPosition:UICollectionViewScrollPositionTop animated:YES];
}

However, if you want to force the scrolling, then try this.

#pragma mark - UICollectionViewDelegate

- (void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath
{
    UICollectionViewCell *cell = [collectionView cellForItemAtIndexPath:indexPath];
    [collectionView setContentOffset:CGPointMake(cell.center.x - collectionView.frame.size.width * 0.5, cell.frame.origin.y) animated:YES];
}

Answer 2

You can also implement the UIScrollViewDelegate method scrollViewShouldScrollToTop: and return YES if the passed in scroll view is equal to the one that you want to scroll to the top:

-(BOOL) scrollViewShouldScrollToTop:(UIScrollView*) scrollView 
{
    if (scrollView == self.myTableView)
       {
          return YES;
       }
    else 
       {
          return NO;
       }
}

if you don't have more than one scroll view/table view/collection view on screen