title: Show Navigation Bar on Android KitKat after hiding it
body: <p>In my app I want to let the user hide or show the Navigation Bar (back, home, menu). The System Bar (battery, wifi, notifications) should always be hidden.</p>
  
  <p>I hide the System Bar with this code:</p>
  
  <pre><code>getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN);
              requestWindowFeature(Window.FEATURE_NO_TITLE);     
  </code></pre>
  
  <p>And I am successfully hiding the Navigation Bar with these flags: </p>
  
  <pre><code>final static int flagsHide = View.SYSTEM_UI_FLAG_LAYOUT_STABLE
                      | View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION
                      | View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN
                      | View.SYSTEM_UI_FLAG_HIDE_NAVIGATION
                      | View.SYSTEM_UI_FLAG_FULLSCREEN
                      | View.SYSTEM_UI_FLAG_IMMERSIVE_STICKY;
  </code></pre>
  
  <p>But I haven't found on how to show the Navigation Bar again. Can I do that with flags or do I need something else? The System Bar has to stay invisible.</p>