code: private void addRefreshButton() {
  
          Button button = CmsToolBar.createButton(
              FontOpenCms.RESET,
              CmsVaadinUtils.getMessageText(Messages.GUI_LOGFILE_REFRESH_FILEVIEW_0));
          button.addClickListener(new ClickListener() {
  
              private static final long serialVersionUID = 1L;
  
              public void buttonClick(ClickEvent event) {
  
                  m_fileView.updateView();
  
              }
          });
          m_uiContext.addToolbarButton(button);
      }
docs: Button to refresh the file view.<p>