Flutter Shared Preferences Util

Flutter Shared Preferences Util :

Screenshot :

main.dart

import 'package:flutter/material.dart';

import 'SpUtil.dart';

void main() async {
  await SpUtil.getInstance();
  runApp(MyApp());
}

class MyApp extends StatefulWidget {
  @override
  State<StatefulWidget> createState() {
    return MyAppState();
  }
}

class MyAppState extends State<MyApp> {
  @override
  void initState() {
    super.initState();

    SpUtil.putString("username", "Flutter Tutorial");

    List<String> list = new List();
    list.add("Flutter");
    list.add("Android");
    SpUtil.putStringList("subject", list);

    List<String> dataList =
    SpUtil.getStringList("subject", defValue: list);

    print('Tag' + dataList.length.toString());
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
        home: Scaffold(
      appBar: AppBar(
        title: Text('Flutter Tutorial SharedPreferences'),
      ),
      body: Container(child: Text(SpUtil.getString("username"))),
    ));
  }
}

SpUtil.dart

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

// SharedPreferences
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) {
          // keep local instance till it is fully initialized.
          var singleton = SpUtil._();
          await singleton._init();
          _singleton = singleton;
        }
      });
    }
    return _singleton;
  }

  SpUtil._();

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

  // put object
  static Future<bool> putObject(String key, Object value) {
    if (_prefs == null) return null;
    return _prefs.setString(key, value == null ? "" : json.encode(value));
  }

  // get obj
  static T getObj<T>(String key, T f(Map v), {T defValue}) {
    Map map = getObject(key);
    return map == null ? defValue : f(map);
  }

  // get object
  static Map getObject(String key) {
    if (_prefs == null) return null;
    String _data = _prefs.getString(key);
    return (_data == null || _data.isEmpty) ? null : json.decode(_data);
  }

  // put object list
  static Future<bool> putObjectList(String key, List<Object> list) {
    if (_prefs == null) return null;
    List<String> _dataList = list?.map((value) {
      return json.encode(value);
    })?.toList();
    return _prefs.setStringList(key, _dataList);
  }

  // get obj list
  static List<T> getObjList<T>(String key, T f(Map v),
      {List<T> defValue = const []}) {
    List<Map> dataList = getObjectList(key);
    List<T> list = dataList?.map((value) {
      return f(value);
    })?.toList();
    return list ?? defValue;
  }

  // get object list
  static List<Map> getObjectList(String key) {
    if (_prefs == null) return null;
    List<String> dataLis = _prefs.getStringList(key);
    return dataLis?.map((value) {
      Map _dataMap = json.decode(value);
      return _dataMap;
    })?.toList();
  }

  // get string
  static String getString(String key, {String defValue = ''}) {
    if (_prefs == null) return defValue;
    return _prefs.getString(key) ?? defValue;
  }

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

  // get bool
  static bool getBool(String key, {bool defValue = false}) {
    if (_prefs == null) return defValue;
    return _prefs.getBool(key) ?? defValue;
  }

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

  // get int
  static int getInt(String key, {int defValue = 0}) {
    if (_prefs == null) return defValue;
    return _prefs.getInt(key) ?? defValue;
  }

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

  // get double
  static double getDouble(String key, {double defValue = 0.0}) {
    if (_prefs == null) return defValue;
    return _prefs.getDouble(key) ?? defValue;
  }

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

  // get string list
  static List<String> getStringList(String key,
      {List<String> defValue = const []}) {
    if (_prefs == null) return defValue;
    return _prefs.getStringList(key) ?? defValue;
  }

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

  // get dynamic
  static dynamic getDynamic(String key, {Object defValue}) {
    if (_prefs == null) return defValue;
    return _prefs.get(key) ?? defValue;
  }

  // have key
  static bool haveKey(String key) {
    if (_prefs == null) return null;
    return _prefs.getKeys().contains(key);
  }

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

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

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

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

pubspec.yaml

name: fluttertutorial
description: A new Flutter application.

version: 1.0.0+1

environment:
  sdk: ">=2.1.0 <3.0.0"

dependencies:
  flutter:
    sdk: flutter

  shared_preferences:
  synchronized:

dev_dependencies:
  flutter_test:
    sdk: flutter

flutter:
  uses-material-design: true

The flutter tutorial  is a website that bring you the latest and amazing resources of code. All the languages codes are included in this website. The languages like flutter, android, java,kotlin etc.with the help of this languages any user can develop the beautiful application

For more information about Flutter. visit www.fluttertutorial.in