问题
Currently, I am working around routes and i wanted to set initialRoute in my app based on sharedPreferences value.
I am using Statedulwidget for my MaterialAppWidget and using setState() method once the data from sharedPrefs is fetched. But, every time i am getting the same screen.
class MyApp extends StatefulWidget {
@override
_MyAppState createState() => _MyAppState();
}
class _MyAppState extends State<MyApp> {
int initScreen = 0;
initPrefs() async {
SharedPreferences prefs = await SharedPreferences.getInstance();
initScreen = prefs.getInt("initScreen");
print("initScreen ${initScreen}");
setState(() {});
}
@override
void initState() {
super.initState();
initPrefs();
}
@override
Widget build(BuildContext context) {
print("initScreen2 ${initScreen}");
return MaterialApp(
debugShowCheckedModeBanner: false,
title: 'Flutter Authentication',
theme: ThemeData(
primarySwatch: Colors.blue,
),
initialRoute: initScreen == 0 || initScreen == null
? MediatorPage.routeName
: PopUntilPage.routeName,
routes: {
CloudGroupCreate.routeName: (context) => CloudGroupCreate(),
CloudDashboard.routeName: (context) => CloudDashboard(),
PopUntilPage.routeName: (context) => PopUntilPage(),
ProviderWithFutureBuilderApp.routeName: (context) =>
ProviderWithFutureBuilderApp(),
MediatorPage.routeName: (context) => MediatorPage(),
},
);
}
}
I do not want to use direct widget using home property app. I just want to navigate through only and only using named routes.
Can anyone suggest how to do it properly ?
Thanks.
回答1:
You need to init SharedPreferences in main() and use WidgetsFlutterBinding.ensureInitialized
You can copy paste run full code below
In demo , I set initScreen to 12
code snippet
int initScreen;
Future<void> main() async {
WidgetsFlutterBinding.ensureInitialized();
SharedPreferences prefs = await SharedPreferences.getInstance();
await prefs.setInt("initScreen",12);
initScreen = await prefs.getInt("initScreen");
print('initScreen ${initScreen}');
runApp(MyApp());
}
...
initialRoute: initScreen == 0 || initScreen == null
? "/"
: "first",
routes: {
'/': (context) => MyHomePage(title: "demo",),
"first": (context) => FirstPage(),
},
working demo
full code
import 'package:flutter/material.dart';
import 'package:shared_preferences/shared_preferences.dart';
//void main() => runApp(MyApp());
int initScreen;
Future<void> main() async {
WidgetsFlutterBinding.ensureInitialized();
SharedPreferences prefs = await SharedPreferences.getInstance();
await prefs.setInt("initScreen",12);
initScreen = await prefs.getInt("initScreen");
print('initScreen ${initScreen}');
runApp(MyApp());
}
class MyApp extends StatelessWidget {
// This widget is the root of your application.
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
// This is the theme of your application.
//
// Try running your application with "flutter run". You'll see the
// application has a blue toolbar. Then, without quitting the app, try
// changing the primarySwatch below to Colors.green and then invoke
// "hot reload" (press "r" in the console where you ran "flutter run",
// or simply save your changes to "hot reload" in a Flutter IDE).
// Notice that the counter didn't reset back to zero; the application
// is not restarted.
primarySwatch: Colors.blue,
),
initialRoute: initScreen == 0 || initScreen == null
? "/"
: "first",
routes: {
'/': (context) => MyHomePage(title: "demo",),
"first": (context) => FirstPage(),
},
//home: MyHomePage(title: 'Flutter Demo Home Page'),
);
}
}
class MyHomePage extends StatefulWidget {
MyHomePage({Key key, this.title}) : super(key: key);
// This widget is the home page of your application. It is stateful, meaning
// that it has a State object (defined below) that contains fields that affect
// how it looks.
// This class is the configuration for the state. It holds the values (in this
// case the title) provided by the parent (in this case the App widget) and
// used by the build method of the State. Fields in a Widget subclass are
// always marked "final".
final String title;
@override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
int _counter = 0;
void _incrementCounter() {
setState(() {
// This call to setState tells the Flutter framework that something has
// changed in this State, which causes it to rerun the build method below
// so that the display can reflect the updated values. If we changed
// _counter without calling setState(), then the build method would not be
// called again, and so nothing would appear to happen.
_counter++;
});
}
@override
Widget build(BuildContext context) {
// This method is rerun every time setState is called, for instance as done
// by the _incrementCounter method above.
//
// The Flutter framework has been optimized to make rerunning build methods
// fast, so that you can just rebuild anything that needs updating rather
// than having to individually change instances of widgets.
return Scaffold(
appBar: AppBar(
// Here we take the value from the MyHomePage object that was created by
// the App.build method, and use it to set our appbar title.
title: Text(widget.title),
),
body: Center(
// Center is a layout widget. It takes a single child and positions it
// in the middle of the parent.
child: Column(
// Column is also a layout widget. It takes a list of children and
// arranges them vertically. By default, it sizes itself to fit its
// children horizontally, and tries to be as tall as its parent.
//
// Invoke "debug painting" (press "p" in the console, choose the
// "Toggle Debug Paint" action from the Flutter Inspector in Android
// Studio, or the "Toggle Debug Paint" command in Visual Studio Code)
// to see the wireframe for each widget.
//
// Column has various properties to control how it sizes itself and
// how it positions its children. Here we use mainAxisAlignment to
// center the children vertically; the main axis here is the vertical
// axis because Columns are vertical (the cross axis would be
// horizontal).
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),
), // This trailing comma makes auto-formatting nicer for build methods.
);
}
}
class FirstPage extends StatelessWidget {
@override
Widget build(BuildContext context) {
return Text("First");
}
}
回答2:
A simple way to do this is to just use a flag when the load has completed, then, in build:
return _isLoadComplete? MaterialApp() : Container();
Another option, it seems like the MaterialApp is being cached, and initialRoute does not get run the 2nd time. Using a key seems to fix this:
return MaterialApp(
key: UniqueKey(),
//etc
I'd lean towards the first approach, as there's no point having MaterialApp try and show one view, will immediately replacing it with another.
来源：https://stackoverflow.com/questions/58813924/how-to-set-dynamic-initialroute-based-on-sharedprefs-value-in-flutter