viewWillAppear for subviews

Question

I have UIScrollView with multiple UIVIew subviews. I would like to update the data that is displayed by each UIView when they appear in the visible portion of the UIScrollView.

What is the callback that gets triggered? I tried viewWillAppear, but it does not seem to get called.

Thanks. :)

Answer 1

You have to do the calculation yourself. Implement scrollViewDidScroll: in your scroll view delegate and calculate manually which views are visible (e.g. by checking if CGRectIntersectsRect(scrollView.bounds, subview.frame) returns true.