Question

我无法通过推送到当前导航器的小部件访问提供程序：

import 'package:flutter/material.dart';
import 'package:flutter/foundation.dart';
import 'package:provider/provider.dart';


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

class MyModel with ChangeNotifier {
  String a = 'Test1';
  String b = 'Test2';
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {    

    return MaterialApp(
        title: 'Flutter Demo',
        home: ChangeNotifierProvider(
            create: (context) => MyModel(),
            child: MyHomePage()
        )
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key}) : super(key: key);

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {

  @override
  Widget build(BuildContext context) {    

    return Consumer<MyModel>(
        builder: (context, myModel, child) =>
            Scaffold(
              appBar: AppBar(
                title: Text(myModel.a),
              ),
              floatingActionButton: FloatingActionButton(
                onPressed: () =>
                    Navigator.of(context).push(
                        PageRouteBuilder(
                            pageBuilder: (context, animation, secondaryAnimation) => Page2(),
                        ),
                    ),
                tooltip: 'Press',
                child: Icon(Icons.add),
              ),
            )
    );
  }
}

class Page2 extends StatelessWidget {

  @override
  Widget build(BuildContext context) {
    var myModel = Provider.of<MyModel>(context); // A

    return Scaffold(
              appBar: AppBar(
                title: Text(myModel.b),
              ),
            );
  }
}

我收到此错误：

The following ProviderNotFoundException was thrown building Page2(dirty):
Error: Could not find the correct Provider<MyModel> above this Navigator Widget

问题似乎是Page2小部件中的BuildContext对象与与提供者关联的BuildContext不同。如果我将原始上下文的引用传递给Page2并在（A）点使用该引用，则一切正常，但这似乎并不是解决此问题的好方法。

我通过将Navigator.of(context, rootNavigator: true).context用作Page2的build方法内的上下文，尝试了解决方法here，但是我仍然遇到相同的异常。

Answer 1

Yo必须在根窗口小部件中传递提供程序，以便在导航到另一个页面时可以从任何位置访问该模型，因此您必须将提供程序传递给MaterialApp的父级

 import 'package:flutter/material.dart';
import 'package:flutter/foundation.dart';
import 'package:provider/provider.dart';

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

class MyModel with ChangeNotifier {
  String a = 'Test1';
  String b = 'Test2';
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return ChangeNotifierProvider(
      create: (context) => MyModel(),
      child: MaterialApp(title: 'Flutter Demo', home: MyHomePage()),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key}) : super(key: key);

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  @override
  Widget build(BuildContext context) {
    return Consumer<MyModel>(
        builder: (context2, myModel, child) => Scaffold(
              appBar: AppBar(
                title: Text(myModel.a),
              ),
              floatingActionButton: FloatingActionButton(
                onPressed: () => Navigator.of(context).push(
                  PageRouteBuilder(
                    pageBuilder: (context, animation, secondaryAnimation) =>
                        Page2(),
                  ),
                ),
                tooltip: 'Press',
                child: Icon(Icons.add),
              ),
            ));
  }
}

class Page2 extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    var myModel = Provider.of<MyModel>(context); // A

    return Scaffold(
      appBar: AppBar(
        title: Text(myModel.b),
      ),
    );
  }
}

无法在新页面路线小部件中访问提供商

1 个答案: