title: Minimize app instead of exit on back button
body: <p>Is there a way to minimize the app when pressing the hardware back button?
  I'm currently using <a href="https://facebook.github.io/react-native/docs/backandroid.html" rel="nofollow">BackAndroid</a>, but it exits the app.</p>
  
  <p>Edit:</p>
  
  <p>I have logic involved in JS, overriding the lifecycle method in ReactActivity is not sending the event back to JS. Thus, it doesn't work.</p>
  
  <pre><code>handleBackButton() {
    const { navigator } = this.refs;
    if (navigator) {
      if (navigator.getCurrentRoutes().length &gt; 1) {
        navigator.pop();
        return true;
      } else if (this.props.selectedTab !== HOME) {
        this.props.selectTab(HOME);
        return true;
      }
    }
    return false;
  }
  </code></pre>