应用重启时如何清除所有共享首选项

Question

使用共享首选项来存储用户选择的搜索过滤器。一切正常，因为我可以成功检索和保存共享首选项。我想在应用重启时清除所有那些保存的过滤器。我知道如何清除它，但无法理解我需要在何处添加此代码以重新启动应用程序。

SharedPreferences prefs = await SharedPreferences.getInstance();
return prefs.clear();

Answer 1

您可以在 main()
中完成代码片段

Future<void> main() async {
  WidgetsFlutterBinding.ensureInitialized();

  SharedPreferences prefs = await SharedPreferences.getInstance();
  await prefs.clear();
  runApp(MyApp());
}

完整模拟代码

import 'package:flutter/material.dart';
import 'package:shared_preferences/shared_preferences.dart';

bool seen;

Future<void> main() async {
  WidgetsFlutterBinding.ensureInitialized();

  SharedPreferences prefs = await SharedPreferences.getInstance();

  await prefs.setBool("seen", true);
  seen = await prefs.getBool("seen");
  print(seen.toString());

  await prefs.clear();

  seen = await prefs.getBool("seen");
  print(seen.toString());

  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
        visualDensity: VisualDensity.adaptivePlatformDensity,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

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

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;

  void _incrementCounter() {
    setState(() {
      _counter++;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      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.headline4,
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _incrementCounter,
        tooltip: 'Increment',
        child: Icon(Icons.add),
      ),
    );
  }
}

输出

I/flutter (13634): true
I/flutter (13634): null

应用重启时如何清除所有共享首选项

How to clear all shared preferences when app restart

flutter

sharedpreferences

flutter-layout