PreferenceUtils

preference_utils.dart

import 'package:shared_preferences/shared_preferences.dart';

class PreferenceUtils {
  static Future<SharedPreferences> get _instance async =>
      _prefsInstance ??= await SharedPreferences.getInstance();
  static SharedPreferences _prefsInstance;

  /// Call this method from iniState() function of mainApp() fo create instance [PreferenceUtils]
  static Future<SharedPreferences> init() async {
    _prefsInstance = await _instance;
    return _prefsInstance;
  }

  /// Use it when you need to check if data exists for a given key.
  ///
  /// return true if storage contains value by given [key]
  static Future<bool> containsKey(String key) async {
    return _prefsInstance.containsKey(key);
  }

  static Future<String> getString(String key, [String defValue]) async {
    return _prefsInstance.getString(key) ?? defValue ?? "";
  }

  static Future<bool> setString(String key, String value) async {
    var prefs = await _instance;
    return prefs?.setString(key, value) ?? Future.value(false);
  }

  static Future<bool> remove(String key) async {
    if (_prefsInstance.containsKey(key)) {
      return _prefsInstance.remove(key);
    } else {
      return true;
    }
  }
}

Gist for work with preference in flutter