如何防止UIScrollView拦截其自身视图层次结构之外的触摸？

Question

My understanding of touch handling is that when a view is touched, if it itself doesn't handle touches, it 'hands' the touches up the view hierarchy until they are either handled, or you're at the top and they're discarded. (In essence, it's recursion; it hands the touches up to their subview, at which point the same 'upward' direction functions are called to pass it upward).

I'm in an odd situation where a UIScrollView -- which SHOULD intercept and handle any and all touches from it's children -- appears to be intercepting the touches of a UIImageView placed 'on top' of it. Remove the scroll view, and touches work properly. The problem is, the UIImageView in question is NOT a child of the UIScrollView; it's a sibling.

So my question becomes twofold: first, how do I stop it from 'stealing' these touches, and two, how can it be stealing them in the first place?

Answer 1

Try setting userInteractionEnabled to YES on the UIImageView. If userInteractionEnabled is set to NO (which should be the default for a UIImageView), then touches would be passed down to the object below it -- the UIScrollView.