code: void asyncUpdate() {
  
          CmsRpcAction<Boolean> action = new CmsRpcAction<Boolean>() {
  
              @Override
              public void execute() {
  
                  start(200, false);
                  m_controller.getContainerpageService().checkContainerpageOrElementsChanged(
                      CmsCoreProvider.get().getStructureId(),
                      CmsContainerpageController.get().getData().getDetailId(),
                      CmsContainerpageController.get().getData().getLocale(),
                      this);
              }
  
              @Override
              protected void onResponse(Boolean result) {
  
                  stop(false);
                  boolean changed = result.booleanValue();
                  setChanged(changed);
              }
  
          };
          action.execute();
      }
docs: Fires off an RPC request to check for the elements state and then updates the button accordingly.<p>