shared_preferences: ^0.5.+

import 'dart:async';

import 'package:shared_preferences/shared_preferences.dart';

/// 用来做shared_preferences的存储

class SpUtil {

  static SpUtil _instance;

  static Future<SpUtil> get instance async {

    return await getInstance();

  }

  static SharedPreferences _spf;

  SpUtil._();

  Future _init() async {

    _spf = await SharedPreferences.getInstance();

  }

  static Future<SpUtil> getInstance() async  {

    if (_instance == null) {

      _instance = new SpUtil._();

      await _instance._init();

    }

    return _instance;

  }

  static bool _beforeCheck() {

    if (_spf == null) {

      return true;

    }

    return false;

  }

  // 判断是否存在数据

  bool hasKey(String key) {

    Set keys = getKeys();

    return keys.contains(key);

  }

  Set<String> getKeys() {

    if (_beforeCheck()) return null;

    return _spf.getKeys();

  }

  get(String key) {

    if (_beforeCheck()) return null;

    return _spf.get(key);

  }

  getString(String key) {

    if (_beforeCheck()) return null;

    return _spf.getString(key);

  }

  Future<bool> putString(String key, String value) {

    if (_beforeCheck()) return null;

    return _spf.setString(key, value);

  }

  bool getBool(String key) {

    if (_beforeCheck()) return null;

    return _spf.getBool(key);

  }

  Future<bool> putBool(String key, bool value) {

    if (_beforeCheck()) return null;

    return _spf.setBool(key, value);

  }

  int getInt(String key) {

    if (_beforeCheck()) return null;

    return _spf.getInt(key);

  }

  Future<bool> putInt(String key, int value) {

    if (_beforeCheck()) return null;

    return _spf.setInt(key, value);

  }

  double getDouble(String key) {

    if (_beforeCheck()) return null;

    return _spf.getDouble(key);

  }

  Future<bool> putDouble(String key, double value) {

    if (_beforeCheck()) return null;

    return _spf.setDouble(key, value);

  }

  List<String> getStringList(String key) {

    return _spf.getStringList(key);

  }

  Future<bool> putStringList(String key, List<String> value) {

    if (_beforeCheck()) return null;

    return _spf.setStringList(key, value);

  }

  dynamic getDynamic(String key) {

    if (_beforeCheck()) return null;

    return _spf.get(key);

  }

  Future<bool> remove(String key) {

    if (_beforeCheck()) return null;

    return _spf.remove(key);

  }

  Future<bool> clear() {

    if (_beforeCheck()) return null;

    return _spf.clear();

  }

}

 SpUtil sp = await SpUtil.getInstance();

 int value =sp.getInt(”key“);