Adjust the position of a UICollectionViewCell.

position-cell.m

- (void)scrollViewWillEndDragging:(UIScrollView *)scrollView withVelocity:(CGPoint)velocity targetContentOffset:(inout CGPoint *)targetContentOffset
{
    UICollectionViewFlowLayout *flowLayout = (UICollectionViewFlowLayout*) self.collectionView.collectionViewLayout;
//    CGFloat maxOffset = (kItemWidth + flowLayout.minimumInteritemSpacing) * kMaxCount;
    
    NSInteger item = (targetContentOffset->x / (kItemWidth + flowLayout.minimumInteritemSpacing));
    NSIndexPath *targetPath = [NSIndexPath indexPathForItem:item inSection:0];
    UICollectionViewLayoutAttributes *attrs = [self.collectionView layoutAttributesForItemAtIndexPath:targetPath];

    DebugLog(@"target cell attrs: %@", attrs);
    // place the offset in front of the cell
    targetContentOffset->x = CGRectGetMinX(attrs.frame) - flowLayout.minimumInteritemSpacing;
}