[英]Navigator operation requested with a context that does not include a Navigator - Flutter
[英]Flutter : Navigator operation requested with a context that does not include a Navigator
我有一个场景,我根据它将用户重定向到 HomePage 或 LandingPage 的值检查 SharePreferences 的值。 我不确定我哪里出错了? 但我在下面收到此错误:我想它没有正确获取上下文,我知道如何获取它吗?。
未处理的异常:使用不包含导航器的上下文请求导航器操作。 E/flutter (11533):用于从 Navigator 推送或弹出路由的上下文必须是作为 Navigator 小部件后代的小部件的上下文。
这是我的代码:
import 'package:credit/src/pages/landing.dart';
import 'package:flutter/material.dart';
import 'package:credit/src/pages/credit/home.dart';
import 'package:shared_preferences/shared_preferences.dart';
void main() => runApp(MyApp());
class MyApp extends StatefulWidget {
MyApp({Key key}) : super(key: key);
_LoadingPageState createState() => _LoadingPageState();
}
class _LoadingPageState extends State<MyApp> {
@override
void initState() {
super.initState();
getUserStatus().then((userStatus) {
if (userStatus == null) {
Navigator.of(context)
.push(MaterialPageRoute<Null>(builder: (BuildContext context) {
return LandingPage();
}));
} else {
Navigator.of(context)
.push(MaterialPageRoute<Null>(builder: (BuildContext context) {
return HomePage();
}));
}
});
}
@override
Widget build(BuildContext context) {
return Container(
child: Center(
child: CircularProgressIndicator(),
));
}
}
Future<String> getUserStatus() async {
SharedPreferences prefs = await SharedPreferences.getInstance();
String userStatus = prefs.getString('userstatus');
print("==On Load Check ==");
print(userStatus);
return userStatus;
}
当您调用Navigator.of(context)
框架在附加到提供的context
小部件树中上升并尝试找到最近的Navigator
。
您显示的小部件树没有,因此您需要在小部件树中包含Navigator
。
最简单的选择是将MaterialApp
与作为home
传递的小部件一起使用。 MaterialApp
正在自身内部创建导航器。 ( CupertinoApp
也这样做)
原始示例中的更新代码:
import 'package:credit/src/pages/landing.dart';
import 'package:flutter/material.dart';
import 'package:credit/src/pages/credit/home.dart';
import 'package:shared_preferences/shared_preferences.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
MyApp({Key key}) : super(key: key);
@override
Widget build(BuildContext context) {
return MaterialApp(
home: LoadingPage(),
);
}
}
class LoadingPage extends StatefulWidget {
LoadingPage({Key key}) : super(key: key);
_LoadingPageState createState() => _LoadingPageState();
}
class _LoadingPageState extends State<LoadingPage> { // note type update
@override
void initState() {
super.initState();
getUserStatus().then((userStatus) {
if (userStatus == null) {
Navigator.of(context)
.push(MaterialPageRoute<Null>(builder: (BuildContext context) {
return LandingPage();
}));
} else {
Navigator.of(context)
.push(MaterialPageRoute<Null>(builder: (BuildContext context) {
return HomePage();
}));
}
});
}
@override
Widget build(BuildContext context) {
return Container(
child: Center(
child: CircularProgressIndicator(),
));
}
}
Future<String> getUserStatus() async {
SharedPreferences prefs = await SharedPreferences.getInstance();
String userStatus = prefs.getString('userstatus');
print("==On Load Check ==");
print(userStatus);
return userStatus;
}
我已经改变了我的代码
void main() {
runApp(MyApp());
}
class MyApp extends StatelessWidget {
// This widget is the root of your application.
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Demo App',
theme: ThemeData(
primarySwatch: white,
scaffoldBackgroundColor: Colors.white,
),
home: Scaffold(
appBar: AppBar(
title: Text('Demo App'),
),
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: [
ElevatedButton(
onPressed: () {
Navigator.push(
context,
MaterialPageRoute(
builder: (context) =>
HomeScreen(title: 'Demo Home')));
},
child: Text('Open Home Screen'))
],
),
),
),
);
}
到
void main() {
runApp(MyApp());
}
class MyApp extends StatelessWidget {
// This widget is the root of your application.
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Demo App',
theme: ThemeData(
primarySwatch: white,
scaffoldBackgroundColor: Colors.white,
),
home: InitScreen());
}
}
class InitScreen extends StatelessWidget {
const InitScreen({Key key}) : super(key: key);
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('Demo App'),
),
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: [
ElevatedButton(
onPressed: () {
Navigator.push(
context,
MaterialPageRoute(
builder: (context) =>
HomeScreen(title: 'Demo Home')));
},
child: Text('Open Home Screen'))
],
),
),
);
}
发生了什么变化?
使用InitScreen在MyApp 中为家庭代码创建一个单独的小部件
问题是什么?
当我们尝试使用 Navigator.of(context) 推送 Route 时,flutter 会尝试在给定上下文的小部件树中查找 Navigator。 在最初的代码中,没有带有导航器的小部件。 因此,为家庭代码创建一个单独的小部件。 MyApp 中的 MaterialApp 小部件将具有 Navigator。
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