iOS Autolayout with UIScrollview: Why does content view of scroll view not fill the scroll view?

Question

The following code (called in viewDidLoad) results in a fully red screen. I would expect it to be a fully green screen. Why is it red? And how can I make it all green?

Answer 1

I tried Rob's answer looks fine at first. BUT! if you also enabled zooming, this Autolayout code will get in the way. It keeps resizing the contentView when zooms. That is, if I zoomed in (zoomScale > 1), I won't be able to scroll the the parts outside the screen.

After days of fighting with Autolayout, sadly I couldn't find any solution. In the end, it doesn't even matter (wat? ok, sorry). In the end, I just remove Autolayout on contentView (use a fixed size contentView), and then in layoutSubviews, I adjust the self.scrollView.contentInset. (I'm using Xcode5, iOS 7)

I know this is not a direct solution to this question. But I just want to point out an easy workaround. It works perfectly for centering a fixed-size contentView in a scrollView, with just 2 lines of code! Hope it may help someone ;)

- (void)layoutSubviews {
    [super layoutSubviews];

    // move contentView to center of scrollView by changing contentInset,
    // because I CANNOT set this with AUTOLAYOUT!!!
    CGFloat topInset = (self.frame.size.height - self.contentView.frame.size.height)/2;
    self.scrollView.contentInset = UIEdgeInsetsMake(topInset, 0, 0, 0);
}