@Override
 protected void componentHidden() {
   super.componentHidden();
   if (null != content) {
     // notify components down the hierarchy tree that they no long
     // need to periodically refresh their content (e.g. RSS feeds)
     remove(content);
   }
 }
 @Override
 protected void componentHidden() {
   super.componentHidden();
   hc.componentHidden();
 }