title: RecyclerView hangs main thread with many elements
body: <p>I have a <code>RecyclerView</code> with an adapter that is based on a <code>List</code> of items. When I have ~400 elements in the adapter, I see the main thread hang for  about 1-2 seconds at the point when I notify the adapter that I've set new data.</p>
  <p>I've method traced it and it's just busy deep in the view hierarchy (starts in <code>ViewRootImpl.performTraversal()</code>).  This doesn't make sense, as I'd expect it only to be rendering the 10-ish elements that are actually visible which should be lightning fast.</p>
  <p>Am I missing some aspect of <code>RecyclerView</code>?</p>
  <h2>Edit</h2>
  <p>It's calling <code>onBindViewHolder()</code> for every element in the list. This doesn't seem correct.</p>
  <h2>Edit</h2>
  <p>If I give my RecyclerView a static height, it solves the problem. Not a solution in itself but hopefully points in a direction.</p>