如何在颤动中将数据从一个小部件传递到另一个小部件？

Question

我想将数据从一个小部件传递到另一个小部件。 我正在从 firebase 获取数据，我希望通过小部件传递该数据。 如何将数据从一个屏幕传递到另一个屏幕。 这就是我的代码的样子。

class Home extends StatefulWidget {
  @override
  _HomeState createState() => _HomeState();
}

class _HomeState extends State<Home> {
  int _currentindex = 0;
  final List<Widget> _children = [
    Dashboard(),
    Search(),

  ];

  void onTappedBar(int index) {
    setState(() {
      _currentindex = index;
    });
  }

  @override
  Widget build(BuildContext context) {
    final user = Provider.of<User>(context);
    return StreamBuilder<UserData>(
        stream: DatabaseService(uid: user.uid).userData,
        builder: (context, snapshot) {
          if (snapshot.hasData) {
            UserData userData = snapshot.data;
            return return Scaffold(
      backgroundColor: Color(0xFFf6f5fb),
      body: _children[_currentindex],
      bottomNavigationBar: CurvedNavigationBar(
        onTap: onTappedBar,
        index: _currentindex,
        items: <Widget>[
          Icon(
            Icons.home,
          ),
          Icon(
            Icons.search,     
        ],
      ),
    );
        });
  }
}

从此小部件中，数据从 firebase 加载。现在我想将 snapshot.data 传递给 Dashboard() 小部件和 Search() 小部件。

我想显示用户名 Dashboard()。 这就是我的 ```Dashboard()`` 小部件的例子

class Dashboard extends StatefulWidget {
  @override
  _DashboardState createState() => _DashboardState();
}

class _DashboardState extends State<Dashboard> {
  @override
  Widget build(BuildContext context) {
    return Center(
      child: Text('Here i want display the data')
      ),
    );
  }
}

这是模型类：

class User {
  final String uid;

  User({this.uid});
}

class UserData {

  final String uid;
  final String username;
  final String phonenumber;

  UserData({ this.uid, this.username, this.phonenumber });
}

Answer 1

如果是像你这样的简单场景，请通过构造函数：

class Dashboard extends StatefulWidget {
  final UserData userData;

  // userData is not optional-named parameter
  const Dashboard(this.userData, {Key key}) : super(key: key);
  @override
  _DashboardState createState() => _DashboardState();
}

class _DashboardState extends State<Dashboard> {
  @override
  Widget build(BuildContext context) {
    final UserData userData = widget.userData;//do something with user
    return Center(
        child: Text('user is ${user.username}')
    ),
    );
  }
}

和HomeState（不要将小部件保存为类的字段，动态创建它们）：

class _HomeState extends State<Home> {
  int _currentindex = 0;

  void onTappedBar(int index) {
    setState(() {
      _currentindex = index;
    });
  }

  @override
  Widget build(BuildContext context) {
    final user = Provider.of<User>(context);
    return StreamBuilder<UserData>(
        stream: DatabaseService(uid: user.uid).userData,
    builder: (context, snapshot) {
    if (snapshot.hasData) {
    UserData userData = snapshot.data;
    return  Scaffold(
    backgroundColor: Color(0xFFf6f5fb),
    body: Column(
               children: [
                 Dashboard(userData),
                 Search(userData),
                 ],
    ),
    bottomNavigationBar: CurvedNavigationBar(
    onTap: onTappedBar,
    index: _currentindex,
    items: <Widget>[
    Icon(
    Icons.home,
    ),
    Icon(
    Icons.search,
    ],
    ),
    );
    });
    }
  }