title: How to hide navigation bar permanently in android activity?
body: <p>I want to hide navigation bar permanently in my activity(not whole system ui).
  now i'm using this piece of code   </p>
  
  <pre><code>getWindow().getDecorView().setSystemUiVisibility(View.SYSTEM_UI_FLAG_HIDE_NAVIGATION);
  </code></pre>
  
  <p>It hides the bar but when user touches the screen it showing again. is there  any way to hide it permanently until activity <code>onStop()</code>;</p>