code: @UiHandler("m_addButton")
      void addButtonClick(ClickEvent e) {
  
          if (null != m_newDate.getValue()) {
              m_dateList.addDate(m_newDate.getValue());
              m_newDate.setValue(null);
              if (handleChange()) {
                  m_controller.setDates(m_dateList.getDates());
              }
          }
      }
docs: Handle click on "Add" button.
  @param e the click event.