title: onBackPressed to hide Not destroy activity
body: <p>i know how to cancel back keypress, so that the activity / main window stays visible:</p>
  
  <pre><code>public void onBackPressed() {
      return;             
  }
  </code></pre>
  
  <p>my aim is to hide the activity, however, without finishing it, how do you do that in the onBackPressed event? </p>
  
  <p>i.e. I would like to get as far as onPause(), but not evoke the onBackPressed() default behaviour that essentially calls finish(). another way to put it is that i would like to mimic onUserLeaveHint() ?</p>
  
  <p>any help appreciated!</p>