Flutter PopupMenuButton示例 PopupWindow

import 'package:flutter/material.dart';

void main() => runApp(new MyApp());

enum ConferenceItem { AddMember, LockConference, ModifyLayout, TurnoffAll }

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    // TODO: implement build
    return new MaterialApp(
      home: new Scaffold(
        body: Center(
          child: FlatButton(
              onPressed: null,
              child: PopupMenuButton<ConferenceItem>(
                onSelected:(item){} ,
                  itemBuilder: (builder) => <PopupMenuEntry<ConferenceItem>>[
                        const PopupMenuItem<ConferenceItem>(
                          child: Text("添加成员"),
                          value: ConferenceItem.AddMember,
                        ),
                        const PopupMenuItem(
                          child: Text("锁定会议"),
                          value: ConferenceItem.LockConference,
                        ),
                        const PopupMenuItem(
                          child: Text("修改布局"),
                          value: ConferenceItem.ModifyLayout,
                        )
                      ])),
        ),
      ),
    );
  }
}

参考：Flutter 技术入门与实战