title: Outer Recyclerview not receiving scroll events of inner Recyclerview
body: <p>I followed this tutorial to implement the behaviors for both hiding the toolbar and the FAB when scrolled: <a href="https://mzgreen.github.io/2015/06/23/How-to-hideshow-Toolbar-when-list-is-scrolling(part3)/" rel="nofollow noreferrer">https://mzgreen.github.io/2015/06/23/How-to-hideshow-Toolbar-when-list-is-scrolling(part3)/</a></p>
  
  <p>I have pasted a demo of what the behavior looks like below.</p>
  
  <p><a href="https://i.stack.imgur.com/79ec5.gif" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/79ec5.gif" alt="scrolling with fab"></a></p>
  
  <p>Now instead of those individual items within the recyclerview in the tabs holding just a textView, I have coded it so that they hold a picture (ImageView) and below it, a recyclerview showing a list of items.</p>
  
  <p>Hence, there is an outer recyclerview that contains a list of inner recyclerviews.</p>
  
  <p>The inner recyclerview does not scroll - I disabled it by following the answer in this thread by overriding the method canScrollVertically(): <a href="https://stackoverflow.com/questions/30222310/disable-scrolling-in-child-recyclerview-android">Disable Scrolling in child Recyclerview android</a>. I also tried enabling the scrolling for the inner recyclerview, but I experienced the same problem.</p>
  
  <p>The outer recyclerview does scroll and has the behavior that shows/hides the toolbar and the FAB.</p>
  
  <p>When I scroll by holding onto the picture (ImageView), the app behavior works perfectly fine, showing and hiding the toolbar and FAB. However, when I have my finger on the inner recyclerview to scroll, the outer recyclerview scrolls and the list moves up and down, but the behavior of show/hiding the toolbar and FAB is never activated. </p>
  
  <p>I have a feeling that this is because the inner recyclerview had intercepted the scroll and the outer recyclerview did not get the scroll event to activate the behavior.</p>
  
  <p>Does anyone know how to make sure the outer recyclerview also gets the scroll event so that the behavior works?</p>