如何根据flutter中的sharedPrefs值设置动态initialRoute? [英] How to set dynamic initialRoute based on sharedPrefs value in flutter?

问题描述

目前，我正在处理路由，我想根据 sharedPreferences 值在我的应用程序中设置 initialRoute.

Currently, I am working around routes and i wanted to set initialRoute in my app based on sharedPreferences value.

我将 Statedulwidget 用于我的 MaterialAppWidget，并在从 sharedPrefs 获取数据后使用 setState() 方法.但是，每次我都看到相同的屏幕.

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(),
        },
        );
  }
}

我不想通过家庭财产应用程序使用直接小部件.我只想浏览并且只使用命名路线.

I do not want to use direct widget using home property app. I just want to navigate through only and only using named routes.

谁能建议如何正确地做到这一点?

Can anyone suggest how to do it properly ?

谢谢.

推荐答案

您需要在 main() 中初始化 SharedPreferences 并使用 WidgetsFlutterBinding.ensureInitialized
您可以在下面复制粘贴运行完整代码
在演示中，我将 initScreen 设置为 12


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

代码片段

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(),
      },

工作演示

完整代码

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");
  }
}

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