title: android: dynamically change FAB(Floating Action Button) icon from code
body: <p>How to change FAB icon in an Activity during runtime. I have this code -></p>
  
  <pre><code>FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fabMainActivity);
  </code></pre>
  
  <p>I know this is possible using <code>fab.setBackgroundDrawable();</code> but i am a newbie to android, don't understand how to do this.</p>
  
  <p>Any help will be highly appreciated.</p>
  
  <p>Thanks</p>