多供应商不能在扑朔迷离的物质应用程序中工作?
问题内容:
我已经创建了一个应用程序,并且使用了MultiProvider,但是当我在MaterialApp中使用它时,它不起作用
我想用它来改变应用主题的颜色,但是
它给我一个错误:
*注意:当我在任何其他屏幕上使用帖子提供程序时,它将起作用。
我的代码:
import 'package:blog_app/provider/posts.dart';
import 'package:blog_app/provider/settings.dart';
import 'package:blog_app/screens/splash_screen.dart';
import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
void main() {
runApp(MyApp());
}
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MultiProvider(
providers: [
ChangeNotifierProvider<Posts>(
builder: (context) => Posts(),
),
ChangeNotifierProvider<Settings>(
builder: (context) => Settings(),
),
],
child: MaterialApp(
darkTheme: Provider.of<Settings>(context).darkModeEnabled ? ThemeData.dark() : ThemeData.light(),
debugShowCheckedModeBanner: false,
title: 'Blogy',
theme: ThemeData(
primaryColor: Colors.deepPurple[900],
cursorColor: Colors.deepPurple[900],
accentColor: Colors.deepPurple[900],
fontFamily: 'Ubuntu',
),
home: SplashScreen(),
),
);
}
}
错误 :-
I/flutter ( 9316): The following ProviderNotFoundError was thrown building MyApp(dirty):
I/flutter ( 9316): Error: Could not find the correct Provider<Settings> above this MyApp Widget
I/flutter ( 9316):
I/flutter ( 9316): To fix, please:
I/flutter ( 9316):
I/flutter ( 9316): * Ensure the Provider<Settings> is an ancestor to this MyApp Widget
I/flutter ( 9316): * Provide types to Provider<Settings>
I/flutter ( 9316): * Provide types to Consumer<Settings>
I/flutter ( 9316): * Provide types to Provider.of<Settings>()
问题答案:
没有错误下面的测试代码的工作,你可以用你的情况下,测试
使用Consumer
包MaterialApp
程式码片段
return MultiProvider(
providers: [
ChangeNotifierProvider<Posts>(
create: (context) => Posts(),
),
ChangeNotifierProvider<Settings>(
create: (context) => Settings(darkModeEnabled: true),
),
],
child: Consumer<Settings>(builder: (_, settings, child) {
return MaterialApp(
darkTheme:
settings.darkModeEnabled ? ThemeData.dark() : ThemeData.light(),
debugShowCheckedModeBanner: false,
title: 'Blogy',
theme: ThemeData(
primaryColor: Colors.deepPurple[900],
cursorColor: Colors.deepPurple[900],
accentColor: Colors.deepPurple[900],
fontFamily: 'Ubuntu',
),
home: SplashScreen(),
);
}),
);
完整的测试代码
import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
void main() => runApp(MyApp());
class Posts extends ChangeNotifier {}
class Settings extends ChangeNotifier {
bool darkModeEnabled;
Settings({this.darkModeEnabled});
}
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MultiProvider(
providers: [
ChangeNotifierProvider<Posts>(
create: (context) => Posts(),
),
ChangeNotifierProvider<Settings>(
create: (context) => Settings(darkModeEnabled: true),
),
],
child: Consumer<Settings>(builder: (_, settings, child) {
return MaterialApp(
darkTheme:
settings.darkModeEnabled ? ThemeData.dark() : ThemeData.light(),
debugShowCheckedModeBanner: false,
title: 'Blogy',
theme: ThemeData(
primaryColor: Colors.deepPurple[900],
cursorColor: Colors.deepPurple[900],
accentColor: Colors.deepPurple[900],
fontFamily: 'Ubuntu',
),
home: SplashScreen(),
);
}),
);
}
}
class SplashScreen extends StatefulWidget {
SplashScreen({Key key}) : super(key: key);
//final String title;
@override
_SplashScreenState createState() => _SplashScreenState();
}
class _SplashScreenState extends State<SplashScreen> {
int _counter = 0;
void _incrementCounter() {
setState(() {
_counter++;
});
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text("test"),
),
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Text(
'You have pushed the button this many times:',
),
Text(
'$_counter',
style: Theme.of(context).textTheme.display1,
),
],
),
),
floatingActionButton: FloatingActionButton(
onPressed: _incrementCounter,
tooltip: 'Increment',
child: Icon(Icons.add),
),
);
}
}