code: protected void addSubNavEntry(final NavEntry navEntry) {
  
          Button button = m_rootLayout.addSubNavEntry(navEntry);
          button.addClickListener(new ClickListener() {
  
              private static final long serialVersionUID = 1L;
  
              public void buttonClick(ClickEvent event) {
  
                  openSubView(navEntry.getTargetState(), true);
              }
          });
      }
docs: Adds a navigation entry.<p>
  
  @param navEntry the navigation entry