flutter shared_preferences相当于iOS的UserDefaults 安卓的SharedPreferences

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();

  @override
  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")));
                        });
                      }),
                ],
              );
          }),
        ),
      );
    });
  }
}