shared_preferences

shared_preferences 是 Flutter 社区开发的一个本地数据存取插件，它有以下特性：

  • 简单的，异步的，持久化的 key-value 存储系统；
  • 在 Android 上它是基于 SharedPreferences 的；
  • 在 iOS 上它是基于 NSUserDefaults 的；

引入：

  1. dependencies:
  2.   shared_preferences: ^0.5.1+

示例：

  1. import 'dart:async';
  3. import 'package:flutter/material.dart';
  4. import 'package:shared_preferences/shared_preferences.dart';
  6. void main() {
  7.   runApp(new MaterialApp(home: new MyApp()));
  8. }
  10. class MyApp extends StatelessWidget {
  11.   final String mUserName = "userName";
  12.   final _userNameController = new TextEditingController();
  14.   @override
  15.   Widget build(BuildContext context) {
  16.     save() async{
  17.       SharedPreferences prefs = await SharedPreferences.getInstance();
  18.       prefs.setString(mUserName, _userNameController.value.text.toString());
  19.     }
  21.     Future<String> get() async {
  22.       var userName;
  24.       SharedPreferences prefs = await SharedPreferences.getInstance();
  25.       userName = prefs.getString(mUserName);
  26.       return userName;
  27.     }
  29.     return new Builder(builder: (BuildContext context) {
  30.       return new Scaffold(
  31.         appBar: AppBar(
  32.           title: Text("SharedPreferences"),
  33.         ),
  34.         body:  Center(
  35.           child: new Builder(builder: (BuildContext context){
  36.             return
  37.               Column(
  38.                 children: <Widget>[
  39.                   TextField(
  40.                     controller: _userNameController,
  41.                     decoration: InputDecoration(
  42.                         contentPadding: const EdgeInsets.only(top: 10.0),
  43.                         icon:  Icon(Icons.perm_identity),
  44.                         labelText: "请输入用户名",
  45.                         helperText: "注册时填写的名字"
  46.                     ),
  47.                   ),
  48.                   RaisedButton(
  49.                       color: Colors.blueAccent,
  50.                       child: Text("存储"),
  51.                       onPressed: () {
  52.                         save();
  53.                         Scaffold.of(context).showSnackBar(
  54.                             new SnackBar(content:  Text("数据存储成功"))
  55.                         );
  56.                       }
  57.                   ),
  58.                   RaisedButton(
  59.                       color: Colors.greenAccent,
  60.                       child: Text("获取"),
  61.                       onPressed: () {
  62.                         Future<String> userName = get();
  63.                         userName.then((String userName) {
  64.                           Scaffold.of(context).showSnackBar(
  65.                               SnackBar(content: Text("数据获取成功：$userName"))
  66.                           );
  67.                         });
  68.                       }
  69.                   ),
  70.                 ],
  71.               );
  72.           }),
  73.         ),
  74.       );
  75.     });
  76.   }
  77. }

效果：
001.gif

本地存储工具类封装

  1. import 'dart:convert';
  3. import 'package:shared_preferences/shared_preferences.dart';
  5. class Storage {
  7.   Storage();
  9.   static Future get(key) async {
  10.     SharedPreferences prefs = await SharedPreferences.getInstance();
  11.     return json.decode(prefs.getString(key));
  12.   }
  14.   static Future set(key, val) async {
  15.     SharedPreferences prefs = await SharedPreferences.getInstance();
  16.     prefs.setString(key, json.encode(val));
  17.   }
  18. }

使用：

  1. FloatingActionButton(
  2.   onPressed: () async {
  3.     // 存储
  4.     Storage.set('name', { 'a': 'hello' });
  6.     // 获取
  7.     var name = await Storage.get('name');
  8.     print(name['a']); // hello
  9.   },
  10.   child: Icon(Icons.arrow_back),
  11. )

参考资料