UICollectionView horizontal scrolling, deleting last item, animation not working

Question

I have a UICollectionView. It scrolls horizontally, has only a single row of items, and behaves like a paging UIScrollView. I\'m making something along the lines of the Safari t

Answer 1

And here's yet another solution (targetIndexPath is the indexPath of the cell to be removed). This code can simply be placed in a removeCellAtIndexPath:(NSIndexPath*)targetIndexPath method and you're done (assuming my adaptations from my code to public code are correct, otherwise ask me and I'll try to help).

// (Here it's assumed that self.collectionView.collectionViewLayout has been assigned a UICollectionViewFlowLayout before; note the word "FLOW" in that class name) 
UICollectionViewFlowLayout* layout = (UICollectionViewFlowLayout*) self.collectionView.collectionViewLayout;

// Find index path of the last cell in collection view:
NSIndexPath* lastIndexPath = [self lastItemIndexPath];

// Extend content area temporarily to fill out space left by the last row after deletion, if last row is visible:
BOOL lastRowWasVisible = NO;
if ([self.collectionView icn_cellAtIndexPathIsVisible:lastIndexPath]) {

    lastRowWasVisible = YES;

    // Adapt section spacing to temporarily fill out the space potentially left after removing last cell:
    CGFloat cellWithLineSpacingHeight = 79.0f + 8.0f; // Height of my cell + one line spacing
    layout.sectionInset = UIEdgeInsetsMake(0.0f, 0.0f, cellWithLineSpacingHeight, 0.0f);
}

// Remove the cell:
[self.collectionView performBatchUpdates:^{

    [self.collectionView deleteItemsAtIndexPaths:[NSArray arrayWithObject:targetIndexPath]];

} completion:^(BOOL finished) {

    // Only scroll if we had the last row visible:
    if (lastRowWasVisible) {

        NSIndexPath* lastItemIndexPath = [self lastItemIndexPath];

        // Run a custom scroll animation for two reasons; 1. that way we can reset the insets when animation is finished, and 2. using the "animated:YES" option lags here for some reason:
        [UIView animateWithDuration:0.3f animations:^{
            [self.collectionView scrollToItemAtIndexPath:prevItemIndexPath atScrollPosition:UICollectionViewScrollPositionBottom animated:NO];
        } completion:^(BOOL finished) {

            // Reset the space placeholder once having scrolled away from it:
            layout.sectionInset = UIEdgeInsetsMake(0.0f, 0.0f, 0.0f, 0.0f);
        }];
    }
}];

The icn_cellAtIndexPathIsVisible: method is just a category on UICollectionView:

- (BOOL) icn_cellAtIndexPathIsVisible:(NSIndexPath*)indexPath {

    BOOL __block wasVisible = NO;
    [self.indexPathsForVisibleItems enumerateObjectsUsingBlock:^(NSIndexPath* ip, NSUInteger idx, BOOL *stop) {

        if ([ip isEqual:indexPath]) {

            wasVisible = YES;
            *stop = YES;
        }
    }];

    return wasVisible;
}

Update: This only works with one section.