code: @Override
      protected String getReadOnlyValue(final AbstractUIField _uiField)
          throws EFapsException
      {
          final Object valueTmp = _uiField.getValue()
                          .getReadOnlyValue(_uiField.getParent().getMode());
          final String ret = valueTmp == null ? null : EnumUtil.getUILabel((IEnum) valueTmp);
          return ret;
      }
docs: {@inheritDoc}