Flutter 工具类 SpUtil

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GitHub: SpUtil

Pub     : SpUtil

学习Flutter的都知道，Flutter的SharedPreferences不能像Android里面一样直接getSharedPreferences得到，而是Future<SharedPreferences> getInstance() async异步获取。
网上很多都是这样

  static getString(String key) async {
    SharedPreferences prefs = await SharedPreferences.getInstance();
    return prefs.getString(key);
}

SpUtil同步获取字符串

  static String getString(String key) {
    if (_prefs == null) return null;
    return _prefs.getString(key);
  }

SpUtil使用单例模式，使用synchronized Lock实现。仅在App启动需要异步等待,在SpUtil.getInstance()完成后，可同步获取SpUtil.getString("xxx").

class _MyAppState extends State<MyApp> {
  @override
  void initState() {
    super.initState();
    loadAsync();
  }
  void loadAsync() async {
    await SpUtil.getInstance(); //等待Sp初始化完成
    SpUtil.putString("username", "sky224");
    String username = SpUtil.getString("username");
  }
  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
      home: new Scaffold(
        body: new Center(
          child: new Text(' '),
        ),
        floatingActionButton: FloatingActionButton(onPressed: () {
          String username = SpUtil.getString("username"); //同步获取
        }),
      ),
    );
  }
}

SpUtil已经开源到Flutter常用工具类库flustars，欢迎Star，以下是SpUtil源码：

import 'dart:async';

import 'package:shared_preferences/shared_preferences.dart';
import 'package:synchronized/synchronized.dart';

/**
 * @Author: thl
 * @GitHub: https://github.com/Sky24n
 * @Flutter常用工具类: https://github.com/Sky24n/flustars
 * @Description: Sp Util.
 * @Date: 2018/9/8
 */

/// SharedPreferences Util.
class SpUtil {
  static SpUtil _singleton;
  static SharedPreferences _prefs;
  static Lock _lock = Lock();

  static Future<SpUtil> getInstance() async {
    if (_singleton == null) {
      await _lock.synchronized(() async {
        if (_singleton == null) {
          // 保持本地实例直到完全初始化。
          var singleton = SpUtil._();
          await singleton._init();
          _singleton = singleton;
        }
      });
    }
    return _singleton;
  }

  SpUtil._();

  Future _init() async {
    _prefs = await SharedPreferences.getInstance();
  }

  static String getString(String key) {
    if (_prefs == null) return null;
    return _prefs.getString(key);
  }

  static Future<bool> putString(String key, String value) {
    if (_prefs == null) return null;
    return _prefs.setString(key, value);
  }

  static bool getBool(String key) {
    if (_prefs == null) return null;
    return _prefs.getBool(key);
  }

  static Future<bool> putBool(String key, bool value) {
    if (_prefs == null) return null;
    return _prefs.setBool(key, value);
  }

  static int getInt(String key) {
    if (_prefs == null) return null;
    return _prefs.getInt(key);
  }

  static Future<bool> putInt(String key, int value) {
    if (_prefs == null) return null;
    return _prefs.setInt(key, value);
  }

  static double getDouble(String key) {
    if (_prefs == null) return null;
    return _prefs.getDouble(key);
  }

  static Future<bool> putDouble(String key, double value) {
    if (_prefs == null) return null;
    return _prefs.setDouble(key, value);
  }

  static List<String> getStringList(String key) {
    return _prefs.getStringList(key);
  }

  static Future<bool> putStringList(String key, List<String> value) {
    if (_prefs == null) return null;
    return _prefs.setStringList(key, value);
  }

  static dynamic getDynamic(String key) {
    if (_prefs == null) return null;
    return _prefs.get(key);
  }

  static Set<String> getKeys() {
    if (_prefs == null) return null;
    return _prefs.getKeys();
  }

  static Future<bool> remove(String key) {
    if (_prefs == null) return null;
    return _prefs.remove(key);
  }

  static Future<bool> clear() {
    if (_prefs == null) return null;
    return _prefs.clear();
  }

  ///Sp is initialized.
  static bool isInitialized() {
    return _prefs != null;
  }
}