Could not find the correct provider above this widget

问题

I have a problem using Flutter Provider... My flow is like this: After login user id is passed to new widget -> from there it preforms save to db and then it redirects to new widget (Dashboard).

And this is a code of a widget after Login:

return MaterialApp(
      title: title,
      home: Scaffold(
          appBar: AppBar(
            title: Text(title),
          ),
          body: ListView(
            children: <Widget>[
              Container(
                margin: EdgeInsets.all(8.0),
                child: Card(
                  shape: RoundedRectangleBorder(
                      borderRadius: BorderRadius.all(Radius.circular(8.0))),
                  child: InkWell(
                    onTap: () {
                      var user = Provider.of<UserRepository>(context);
                      user.savePreference(user.user.id, "Something");
                      user.navigateToNewPage(Dashboard(), context);
                      print(user.user.id);
                    },

This works:

user.savePreference(user.user.id, "Something");

But this is causing a problem:

user.navigateToNewPage(Dashboard(), context);

In Dashboard widget I am creating this:

 Widget build(BuildContext context) {
    var user = Provider.of<UserRepository>(context);

And in UserRepository I have this:

class UserRepository with ChangeNotifier {
  User user;
  Status _status = Status.Uninitialized;

  Status get status => _status;
  User get getUser => user;

  UserRepository.instance();

Future<void> navigateToNewPage(Widget page, BuildContext context) {
    Navigator.push(context, MaterialPageRoute(builder: (context) => page));
  }

I know this topic has already solved questions, but could not find anything suitable to my problem.

回答1:

Try extracting part of your widget tree that lies below Scaffold to a separate widget. The context you are using now is used to build your top level widget which does not Navigator yet.

The resulting code should look like that:

return MaterialApp(
      title: title,
      home: Scaffold(
          appBar: AppBar(
            title: Text(title),
          ),
          body: LoginWidget()

class LoginWidget extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return ListView(
            children: <Widget>[
              Container(
                margin: EdgeInsets.all(8.0),
                child: Card(
                  shape: RoundedRectangleBorder(
                      borderRadius: BorderRadius.all(Radius.circular(8.0))),
                  child: InkWell(
                    onTap: () {
                      var user = Provider.of<UserRepository>(context);
                      user.savePreference(user.user.id, "Something");
                      user.navigateToNewPage(Dashboard(), context);
                      print(user.user.id);
                    },

...

  }
}

回答2:

Parameter context for Provider.of(context) must be a child of you defined provider.

@override
  Widget build(BuildContext context) {
    // !important here, Scaffold.of(context) returns null
    return Scaffold(
      appBar: AppBar(title: Text('Demo')),
      body: Builder(
        builder: (BuildContext context) {
          return FlatButton(
            child: Text('BUTTON'),
            onPressed: () {
              // here, Scaffold.of(context) returns the locally created Scaffold
              Scaffold.of(context).showSnackBar(SnackBar(
                content: Text('Hello.')
              ));
            }
          );
        }
      )
    );
  }

Official sample: https://api.flutter.dev/flutter/widgets/BuildContext-class.html

This is my code:

  @override
  Widget build(BuildContext context) {
    return MultiProvider(
      providers: [ChangeNotifierProvider<SomeModel>(
        create: (context){
          return SomeModel();
        },
      ),],
      child: Builder(builder: (BuildContext context){
        BuildContext rootContext = context;
        return Container(
//Here to use rootContext is safe
//Provider.of<SomeModel>(rootContext, listen: false);
        );
      }),
    );
}

来源：https://stackoverflow.com/questions/57124258/could-not-find-the-correct-provider-above-this-widget