本地存储

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:

dependencies:
  shared_preferences: ^0.5.1+

示例:

import 'dart:async';
import 'package:flutter/material.dart';
import 'package:shared_preferences/shared_preferences.dart';
void main() {
  runApp(new MaterialApp(home: new MyApp()));
}
class MyApp extends StatelessWidget {
  final String mUserName = "userName";
  final _userNameController = new TextEditingController();
  
  Widget build(BuildContext context) {
    save() async{
      SharedPreferences prefs = await SharedPreferences.getInstance();
      prefs.setString(mUserName, _userNameController.value.text.toString());
    }
    Future<String> get() async {
      var userName;
      SharedPreferences prefs = await SharedPreferences.getInstance();
      userName = prefs.getString(mUserName);
      return userName;
    }
    return new Builder(builder: (BuildContext context) {
      return new Scaffold(
        appBar: AppBar(
          title: Text("SharedPreferences"),
        ),
        body:  Center(
          child: new Builder(builder: (BuildContext context){
            return
              Column(
                children: <Widget>[
                  TextField(
                    controller: _userNameController,
                    decoration: InputDecoration(
                        contentPadding: const EdgeInsets.only(top: 10.0),
                        icon:  Icon(Icons.perm_identity),
                        labelText: "请输入用户名",
                        helperText: "注册时填写的名字"
                    ),
                  ),
                  RaisedButton(
                      color: Colors.blueAccent,
                      child: Text("存储"),
                      onPressed: () {
                        save();
                        Scaffold.of(context).showSnackBar(
                            new SnackBar(content:  Text("数据存储成功"))
                        );
                      }
                  ),
                  RaisedButton(
                      color: Colors.greenAccent,
                      child: Text("获取"),
                      onPressed: () {
                        Future<String> userName = get();
                        userName.then((String userName) {
                          Scaffold.of(context).showSnackBar(
                              SnackBar(content: Text("数据获取成功:$userName"))
                          );
                        });
                      }
                  ),
                ],
              );
          }),
        ),
      );
    });
  }
}

封装

import 'dart:convert';
import 'package:shared_preferences/shared_preferences.dart';
class Storage {
  Storage();
  static Future get(key) async {
    SharedPreferences prefs = await SharedPreferences.getInstance();
    return json.decode(prefs.getString(key));
  }
  static Future set(key, val) async {
    SharedPreferences prefs = await SharedPreferences.getInstance();
    prefs.setString(key, json.encode(val));
  }
}

使用:

FloatingActionButton(
  onPressed: () async {
    // 存储
    Storage.set('name', { 'a': 'hello' });
    // 获取
    var name = await Storage.get('name');
    print(name['a']); // hello
  },
  child: Icon(Icons.arrow_back),
)

参考资料

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