flutter中存储键值对简单数据(相当于前端localstorage概念)

首先需要安装一个官方推荐包：

dependencies:
  flutter:
    sdk: flutter
  shared_preferences: any

// 先获取 shared preferences 
final prefs = await SharedPreferences.getInstance();

// 设置value
prefs.setInt('counter', counter);

//  获取value

final counter = prefs.getInt('counter');

//  删除value

prefs.remove('counter');

支持的类型如下：int, double, bool, string ， stringList

完整例子：

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

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  // This widget is the root of our application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Shared preferences demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(title: 'Shared preferences demo'),
    );
  }
}

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;

  @override
  void initState() {
    super.initState();
    _loadCounter();
  }

  //Loading counter value on start
  _loadCounter() async {
    SharedPreferences prefs = await SharedPreferences.getInstance();
    setState(() {
      _counter = (prefs.getInt('counter') ?? 0);
    });
  }

  //Incrementing counter after click
  _incrementCounter() async {
    SharedPreferences prefs = await SharedPreferences.getInstance();
    setState(() {
      _counter = (prefs.getInt('counter') ?? 0) + 1;
      prefs.setInt('counter', _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.display1,
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _incrementCounter,
        tooltip: 'Increment',
        child: Icon(Icons.add),
      ), // This trailing comma makes auto-formatting nicer for build methods.
    );
  }
}