How to check if child item is visible in ScrollView?

I have a scroll view and have child elements in it (Imagine it’s the GMAIL phone app). How can I check if one child element is visible or not while scrolling in the list? I tried OnBecameVisible and OnBecameInvisible but it seems that they are not even being called.

My intention was to improve the performance on older phones. However I found that the bottle neck is not the viewing/rendering but I hav enabled pixel perfect. As sonn as I removed pixel perfect the performance is up again.