contentView is shorter than UIScrollView - objective-c

Question

I am able to scroll all the way down with the code below:
- (void)viewDidLayoutSubviews {
dispatch_async (dispatch_get_main_queue(), ^ {
CGFloat scrollViewHeight = 0.0f;
for (UIView* view in self.scrollView.subviews) {
scrollViewHeight += view.frame.size.height;
}
[self.scrollView setContentSize:(CGSizeMake(320, scrollViewHeight))];
});
}
but when I scroll, the contentView (in gray) is short and everything below it does not work:
EDIT:

Answer 1

EDIT Two things might be wrong with the layout. (1) The single subview of the scroll view (gray) needs to be large enough to encompass it's subviews, and (2) as the OP implies, so must the scrollView contentSize.
UIView *grayView = // get a pointer to that grayView
CGFloat maxContentY = 0.0;
for (UIView* view in grayView.subviews) {
maxContentY = MAX(maxContentY, CGRectGetMaxY(view.frame));
}
grayView.frame = CGRectMake(0,0, 320,maxContentY);
If that's the only subview of the scrollView, then the contentSize is easy:
[self.scrollView setContentSize:grayView.frame.size];
If there are other subviews, beside the gray one, then my original answer holds also, size the grayView as above and figure the max extent of the other subviews:
We typically aim to make the contentSize.height large enough to encompass the bottom edge of the bottom-most subview.
That's different calculation than the sum of the heights of the subviews, as the OP has it. (Consider a single subview at offset y == 1000 and height == 2. We want a height of 1002, not 2), so...
- (void)viewDidLayoutSubviews {
dispatch_async (dispatch_get_main_queue(), ^ {
CGFloat maxY = 0.0f;
for (UIView* view in self.scrollView.subviews) {
maxY = MAX(maxY, CGRectGetMaxY(view.frame));
}
[self.scrollView setContentSize:(CGSizeMake(320, maxY))];
});
}
The async invocation is harmless but hopefully unnecessary. Either the loop runs in trivial time, or we've added too many subviews.

Answer 2

try this one
- (void)viewDidLayoutSubviews {
dispatch_async (dispatch_get_main_queue(), ^ {
CGRect contentRect = CGRectZero;
for (UIView *view in self.scrollView.subviews)
contentRect = CGRectUnion(contentRect, view.frame);
[self.scrollView setContentSize:contentRect.size];
});
}