title: android - way to be informed when a view is shown within a scrollview?
body: <p>i have a simple question:</p>
  
  <p>suppose i have some views on a scrollView (or a horizontalScrollView) .
  is there any way to add a listener that will tell me when such a view is getting inside and outside the visible area ?</p>
  
  <p>the only similar question i've seen is this:
  <a href="https://stackoverflow.com/questions/4628800/android-how-to-check-if-a-view-inside-of-scrollview-is-visible">Android: how to check if a View inside of ScrollView is visible?</a>
  but i want to be informed when such an event occurs (becoming hidden/visible) .</p>