public void onValueChange(ValueChangeEvent<String> event) {
    String token = event.getValue();
    if (token != null) {
      Presenter presenter = null;

      if (token.equals("list")) {
        IOCBeanDef<ContactsPresenter> bean = manager.lookupBean(ContactsPresenter.class);
        if (bean != null) {
          presenter = bean.getInstance();
        }
      } else if (token.equals("add") || token.equals("edit")) {
        IOCBeanDef<EditContactPresenter> bean = manager.lookupBean(EditContactPresenter.class);
        if (bean != null) {
          presenter = bean.getInstance();
        }
      }

      if (presenter != null) {
        presenter.go(container);
      }
    }
  }