如何在flutter中调用showMenu方法时不丢弃键盘？

import 'package:flutter/services.dart';

FocusScopeNode currentFocus = FocusScopeNode();

FocusScope.of(context).setFirstFocus(currentFocus);

showMenu(
  context: context,
  position: RelativeRect.fromLTRB(100, 100, 0, 0),
  items: [
    PopupMenuItem(
      child: Text('Item 1'),
    ),
    PopupMenuItem(
      child: Text('Item 2'),
    ),
  ],
  elevation: 8.0,
  useRootNavigator: true,
  // 设置focusScopeNode属性
  captureInheritedThemes: false,
  focusScopeNode: currentFocus,
);