docs: @Override
      public boolean onKeyUp (int keyCode, KeyEvent event){
          Fragment frag = getSupportFragmentManager().findFragmentByTag(SAMPLES_FRAGMENT_TAG);
          if (frag==null) {
              return super.onKeyUp(keyCode, event);
          }
          if (!(frag instanceof BaseSampleFragment)) {
              return super.onKeyUp(keyCode,event);
          }
          MapView mMapView = ((BaseSampleFragment)frag).getmMapView();
          if (mMapView==null)
              return super.onKeyUp(keyCode,event);
          switch (keyCode) {
              case KeyEvent.KEYCODE_PAGE_DOWN:
                  mMapView.getController().zoomIn();
                  return true;
              case KeyEvent.KEYCODE_PAGE_UP:
                  mMapView.getController().zoomOut();
                  return true;
          }
          return super.onKeyUp(keyCode,event);
      }