UIImageView is cut off on right side within PageControl after zooming

Question

my image is cut off on the right side after zooming in. if i don't set the offset with cgrect make, then it is not cut off, but i want my image to be centered on the screen. how can i have my image centered and not cut off the right portion after zooming?

- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.

self.view.backgroundColor = [UIColor grayColor];

UIScrollView *mainScrollView = [[UIScrollView alloc] initWithFrame:self.view.bounds];
mainScrollView.pagingEnabled = YES;
mainScrollView.showsHorizontalScrollIndicator = NO;
mainScrollView.showsVerticalScrollIndicator = NO;

CGRect innerScrollFrame = mainScrollView.bounds;

for (NSInteger i = 0; i < 2; i++) {
    UIImageView *imageForZooming = [[UIImageView alloc] initWithImage:[UIImage imageNamed:[NSString stringWithFormat:@"page%d", i + 1]]];
    imageForZooming.tag = VIEW_FOR_ZOOM_TAG;
    imageForZooming.frame = CGRectMake(50, 0, imageForZooming.bounds.size.width, imageForZooming.bounds.size.height);

    UIScrollView *pageScrollView = [[UIScrollView alloc] initWithFrame:innerScrollFrame];
    pageScrollView.minimumZoomScale = 0.5f;
    pageScrollView.maximumZoomScale = 1.0f;
    pageScrollView.contentSize = imageForZooming.bounds.size;
    pageScrollView.delegate = self;
    [pageScrollView addSubview:imageForZooming];

    [mainScrollView addSubview:pageScrollView];

    if (i < 1) {
        innerScrollFrame.origin.x += innerScrollFrame.size.width;
    }

    pageScrollView.zoomScale = 0.5f;
}

mainScrollView.contentSize = CGSizeMake(innerScrollFrame.origin.x + innerScrollFrame.size.width, mainScrollView.bounds.size.height);

[self.view addSubview:mainScrollView];
}

- (UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView {
return [scrollView viewWithTag:VIEW_FOR_ZOOM_TAG];
}

EDIT: here is my view hierarchy

• View
  • mainScrollView
    • innerScrollFrame
      • pageScrollView
        • imageForZooming
    • innerScrollFrame
      • pageScrollView
        • imageForZooming

Answer 1

For anyone else having the same problem in the future, what I did was add the following UIScrollViewDelegate protocol:

- (void)scrollViewDidZoom:(UIScrollView *)scrollView {
    UIView *subView = [scrollView.subviews objectAtIndex:0];
    CGFloat offsetX = (scrollView.bounds.size.width > scrollView.contentSize.width) ? (scrollView.bounds.size.width - scrollView.contentSize.width) * 0.5 : 0.0;
    CGFloat offsetY = (scrollView.bounds.size.height > scrollView.contentSize.height) ? (scrollView.bounds.size.height - scrollView.contentSize.height) * 0.5 : 0.0;
    subView.center = CGPointMake(scrollView.contentSize.width * 0.5 + offsetX, 
        scrollView.contentSize.height * 0.5 + offsetY);
}

i found the answer here: Center content of UIScrollView when smaller

so that the image would be centered after zooming instead of applying the offset that was initially applied. worked like a charm. now when I zoom, none of my image is cut off on either page control, and I can center the image at the beginning of the view.