code: protected void setFileInput(CmsFileInput fileInput) {
  
          // only accept file inputs with a single selected file
          if (fileInput.getFiles().length == 1) {
              if (m_okButton != null) {
                  m_okButton.enable();
              }
              if (m_fileInput != null) {
                  m_fileInput.removeFromParent();
              }
              m_fileInput = fileInput;
              RootPanel.get().add(m_fileInput);
              m_mainPanel.setContainerWidget(createFileWidget(m_fileInput.getFiles()[0]));
          }
      }
docs: Sets the file input.<p>
  
  @param fileInput the file input