iPhone: UIScrollView not scrolling when adding item via IB

I'm trying to make a very simple scrolling page via IB. What I've got is a UIImageView at the top and 2 UIImageViews at the bottom, with a UITextView in the middle. I've disabled the scrolling in the UITextView as I won't the whole page to scroll up and down including开发者_运维技巧 the UIImageViews.

Can anyone tell me why the UIScrollView won't scroll up and down? All of the items above are subviews of UIScrollView via IB.

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You can only scroll in a UIScrollView if the contentSize is larger than the frame. Have you set this?