Question

How does one add a gap/space between multiple images that are added to the UIScrollView?

one example would be photos app, which has black spacing between images when paging.

Answer 1

It’s just basic mathematics..

You add UIImageView as subviews, and compute the space you want knowing the size of your subviews and the contentSize of the scrollView.

EDIT :

This basically build a gallery

-(void)photosGallery
{
    UIScrollView* scrollView = [[UIScrollView alloc] initWithFrame:(CGRect){.origin.x = 0.0f, .origin.y = 0.0f, .size.width = 320.0f, .size.height = 416.0f}];
    scrollView.contentSize = (CGSize){.width = view.frame.size.width, .height = 372.0f};
    scrollView.backgroundColor = [UIColor whiteColor];
    scrollView.showsVerticalScrollIndicator = NO;
    scrollView.showsHorizontalScrollIndicator = NO;
    /// Build gallery
    CGSize thumbSize = (CGSize){.width = 75.0f, .height = 75.0f};
    const CGFloat xSpace = (scrollView.frame.size.width - (thumbSize.width * kPictsPerRow)) / (kPictsPerRow + 1); // kPictsPerRow = Number of pictures in a row
    const CGFloat xInc = thumbSize.width + xSpace;
    const CGFloat yInc = thumbSize.height + 15.0f;
    CGFloat x = xSpace, y = 10.0f;
    for (NSUInteger i = kMaxPictures; i--;)
    {
        UIImageView* pv = [[UIImageView alloc] initWithFrame:(CGRect){.origin.x = x, .origin.y = y, .size = thumbSize}];
        [scrollView addSubview:pv];
        [pv release];
        x += xInc;
        const NSUInteger eor = i % kPictsPerRow;

        if (!eor)
            y += yInc, x = xSpace;
    }
    [scrollView release];
}