code: private void buildActivationButton() {
  
          m_activation = new CmsCheckBox(Messages.get().key(Messages.GUI_MULTISELECT_ACTIVATE_0));
  
          m_activation.addStyleName(I_CmsWidgetsLayoutBundle.INSTANCE.widgetCss().checkboxlabel());
          m_activation.addValueChangeHandler(new ValueChangeHandler<Boolean>() {
  
              public void onValueChange(ValueChangeEvent<Boolean> event) {
  
                  setAllCheckboxEnabled(event.getValue().booleanValue());
  
              }
          });
      }
docs: Adds a button to activate or deactivate the selection.<p>