Flutter之PopupMenuButton

const PopupMenuButton({
Key key,
@required this.itemBuilder,
this.initialValue,//初始值，如果itemBuilder里该值，则会高亮显示
this.onSelected,//选中弹出弹出选项的回调
this.onCanceled,//点屏幕外取消回调,点击屏幕其他地方时调用
this.tooltip,//
this.elevation = 8.0,// 默认值
this.padding = const EdgeInsets.all(8.0),// 默认值
this.child,//修改PopupMenuButton默认三个点的图标为设置的child，不能与icon同时使用
this.icon,//修改PopupMenuButton默认三个点的图标为设置的icon，不能与child同时使用
this.offset = Offset.zero,
})

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: Scaffold(
          appBar: AppBar(
              leading: IconButton(
                  icon: new Container(
                    child: new Icon(Icons.arrow_back),
                  ),
                  onPressed: () {
                    Navigator.pop(context);
                  }),
              title: Text("登陆（Login）"),
              centerTitle: true,
              actions: [
                new PopupMenuButton(
                  itemBuilder: (BuildContext context) {
                  
                    return >[
                      PopupMenuItem(
                        child: Text("分享"),
                        value: "share",
                      ),
                      PopupMenuItem(
                        child: Text("更多"),
                        value: "more",
                      ),
                    ];
                  },
                  onSelected: (String action) {
                    switch (action) {
                      case "share":
                        print("分享 QQ、微信");
                        break;
                      case "more":
                        print("更多");
                        break;
                    }
                  },
                ),
              ]),
          body: Center(
            child: LoginPage(),
          )),
    );
  }
}