code: void showLockedResourceMessage() {
  
          CmsErrorDialog dialog = new CmsErrorDialog(
              Messages.get().key(Messages.ERR_RESOURCE_ALREADY_LOCKED_BY_OTHER_USER_0),
              null);
          dialog.addCloseHandler(new CloseHandler<PopupPanel>() {
  
              public void onClose(CloseEvent<PopupPanel> event) {
  
                  cancelEdit();
              }
          });
          dialog.center();
      }
docs: Shows the locked resource error message.<p>