code: @TargetApi(VERSION_CODES.KITKAT)
      public static void hideSystemUI(Activity activity) {
          // Set the IMMERSIVE flag.
          // Set the content to appear under the system bars so that the content
          // doesn't resize when the system bars hideSelf and show.
          View decorView = activity.getWindow().getDecorView();
          decorView.setSystemUiVisibility(
                  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 // hideSelf nav bar
                          | View.SYSTEM_UI_FLAG_FULLSCREEN // hideSelf status bar
                          | View.SYSTEM_UI_FLAG_IMMERSIVE
          );
      }
docs: This intro hides the system bars.