I created a separate calss page to working with shared preferences from all the different application pages. Save or edit data. I can save String data with ease, but I am facing a problem saving data of type bool. I try to save data of type bool to store the status of the user logged in or not. I searched for solutions for a long time, but couldn't find.
full code:
import 'package:shared_preferences/shared_preferences.dart';
class MyPreferences {
static const ID = "id";
static const STATE = "state";
static final MyPreferences instance = MyPreferences._internal();
static SharedPreferences _sharedPreferences;
String id = "";
String state = "";
MyPreferences._internal() {}
factory MyPreferences() => instance;
Future<SharedPreferences> get preferences async {
if (_sharedPreferences != null) {
return _sharedPreferences;
} else {
_sharedPreferences = await SharedPreferences.getInstance();
state = _sharedPreferences.getString(STATE);
id = _sharedPreferences.getString(ID);
return _sharedPreferences;
}
}
Future<bool> commit() async {
await _sharedPreferences.setString(STATE, state);
await _sharedPreferences.setString(ID, id);
}
Future<MyPreferences> init() async {
_sharedPreferences = await preferences;
return this;
}
}
Can somebody help me to make bool data.
thank you
Just add a couple methods to your class.
void updateLoggedIn(bool value) {
_sharedPreferences.setBool('logged_in', value);
}
bool isLoggedIn() => _sharedPreferences.getBool('logged_in') ?? false;
Then on login just run
MyPreferences.instance.updateLoggedIn(true)
And the same thing passing in false on logout.
Then whenever you want to check logged in status just run
if(MyPreferences.instance.isLoggedIn()) {
// whatever needs to happen
}
Related
In flutter 1.x, I implemented a Config class using the Flutter shared_preferences package; the code looks like this:
import 'package:shared_preferences/shared_preferences.dart';
class Config {
static final Config _config = Config._internal();
factory Config() => _config;
final accessTokenKey = 'accessToken';
String _accessToken;
SharedPreferences prefs;
Config._internal() {
loadData();
}
void loadData() async {
prefs = await SharedPreferences.getInstance();
_accessToken = prefs.getString(accessTokenKey) ?? '';
}
String get accessToken {
return _accessToken;
}
set accessToken(String accessToken) {
_accessToken = accessToken;
_saveString(accessTokenKey, accessToken);
}
_saveString(String key, String value, {String printValue = ''}) {
String printVal = printValue.length > 0 ? printValue : value;
prefs.setString(key, value);
}
}
I’m creating a new project in Flutter 2.x and trying to use the same code, but due to changes associated with null safety I’m having some difficulty getting the updated code just right.
The updated documentation for the package says to initialize the _prefs object like this:
Future<SharedPreferences> _prefs = SharedPreferences.getInstance();
Then create a local prefs object using:
final SharedPreferences prefs = await _prefs;
This is fine, but I don’t want to have to make every class method that uses shared_preferences async then recreate the variable. At the same time I can’t create it as a class variable without initializing it first. Can someone please show me a cleaner way to do this, or do I just have to redeclare it every time I use it?
Also, how do I initialize the config object in my other classes? In my 1.x code, I would just do this:
final Config config = new Config();
then start accessing the properties of the config object. How do I initialize it with all of the async code in the class now?
Here’s where the updated code is today:
import 'package:shared_preferences/shared_preferences.dart';
import '../models/device.dart';
class Config {
static final Config _config = Config._internal();
factory Config() => _config;
final accessTokenKey = 'accessToken';
String _accessToken = '';
Future<SharedPreferences> _prefs = SharedPreferences.getInstance();
Config._internal() {
print('Config constructor');
loadData();
}
Future<void> loadData() async {
final SharedPreferences prefs = await _prefs;
_accessToken = prefs.getString(accessTokenKey) ?? '';
}
String get accessToken {
return _accessToken;
}
set accessToken(String accessToken) {
_accessToken = accessToken;
_saveString(accessTokenKey, accessToken);
}
_saveString(String key, String value, {String printValue = ''}) {
String printVal = printValue.length > 0 ? printValue : value;
print('Config: _saveString("$key", "$printVal")');
final SharedPreferences prefs = await _prefs;
prefs.setString(key, value);
}
}
You can get instance of SharedPreferences as static field in init method:
static SharedPreferences? _prefs; //or: static late SharedPreferences _prefs;
static init() async {
_prefs = await SharedPreferences.getInstance();
}
And call init() somewhere like in build() method of first widget run, for once.Now you can use _prefs everywhere as you want.
If I want to show you a complete class to use SharedPreferences, it looks like this:
import 'package:shared_preferences/shared_preferences.dart';
class SharedPreferencesRepository {
static SharedPreferences? _prefs;
static init() async {
_prefs = await SharedPreferences.getInstance();
}
static putInteger(String key, int value) {
if (_prefs != null) _prefs!.setInt(key, value);
}
static int getInteger(String key) {
return _prefs == null ? 0 : _prefs!.getInt(key) ?? 0;
}
static putString(String key, String value) {
if (_prefs != null) _prefs!.setString(key, value);
}
static String getString(String key) {
return _prefs == null ? 'DEFAULT_VALUE' : _prefs!.getString(key) ?? "";
}
static putBool(String key, bool value) {
if (_prefs != null) _prefs!.setBool(key, value);
}
static bool getBool(String key) {
return _prefs == null ? false : _prefs!.getBool(key) ?? false;
}
}
I hope this useful for you.
If you need to wait for some async work to finish before getting an instance of a class, consider using a static method (not a factory constructor, since constructors must always return the base type).
You can use late fields to allow them to be non-null before you initialize them:
class Config {
late String _accessToken;
String get accessToken => _accessToken;
Config._(); // private constructor to prevent accidental creation
static Future<Config> create() async {
final config = Config();
final preferences = await SharedPreferences.getInstance();
config._accessToken = await preferences.getString('<your key>');
return config;
}
}
If you want to make sure this is initialized before running your app, you can initialize it in your main() method before you call runApp() to give control to the Flutter framework:
Future<void> main() async {
WidgetsFlutterBinding.ensureInitialized(); // make sure all plugins loaded etc.
final config = await Config.create();
print(config.accessToken);
runApp(MyApp());
}
import 'package:flutter/material.dart';
import 'package:shared_preferences/shared_preferences.dart';
class Global {
static SharedPreferences _prefs;
static String key;
static Future init() async {
WidgetsFlutterBinding.ensureInitialized();
_prefs = await SharedPreferences.getInstance();
var _key = _prefs.getString("key");
if (_key != null) {
key = _key;
}
}
static saveKey(value) => _prefs.setString("key", value);
}
Here I create a global class. And I set and get value by this way.
Global.key = value; //set
Global.key; //get
But after I close the app, the value is gone. Any suggestions?
import 'package:flutter/material.dart';
import 'package:shared_preferences/shared_preferences.dart';
class Global {
static SharedPreferences _prefs;
static String key;
String get init => key; // adding a getter
static Future init() async {
WidgetsFlutterBinding.ensureInitialized();
_prefs = await SharedPreferences.getInstance();
var _key = _prefs.getString("key");
if (_key != null) {
key = _key;
}
}
static saveKey(value) => _prefs.setString("key", value);
}
Global().init =value; or Global.init = value; //set
Global().init; //get Global.init; //get
Are you ever calling your Init function in your Main method?
void main() async {
await Global.init();
runApp(MyApp());
}
Assuming you're doing that, the other mistake here is how you're trying to store your value. Use the saveKey function you have in place that's what it's there for. Throw this on one of your pages.
ElevatedButton(
onPressed: () {
Global.saveKey('Test');
},
child: Text('Test'),
),
Your Global class was perfectly fine, its how you were trying to use it. Try this though, only change is that I included a null check so you don't have to create an extra variable that's not used. Also added a print statement that will print the stored value when you re-start the app. It all works fine on my end.
class Global {
static SharedPreferences _prefs;
static String key;
static Future init() async {
WidgetsFlutterBinding.ensureInitialized();
_prefs = await SharedPreferences.getInstance();
key = _prefs.getString('key') ?? ''; // null check here
debugPrint(key);
}
static saveKey(value) => _prefs.setString("key", value);
}
I'm trying to use riverpod for login with a laravel backend. Right now I'm just returning true or false from the repository. I've set a form that accepts email and password. The isLoading variable is just to show a circle indicator. I've run the code and it works but not sure if I'm using riverpod correctly. Is there a better way to do it ?
auth_provider.dart
class Auth{
final bool isLogin;
Auth(this.isLogin);
}
class AuthNotifier extends StateNotifier<Auth>{
AuthNotifier() : super(Auth(false));
void isLogin(bool data){
state = new Auth(data);
}
}
final authProvider = StateNotifierProvider((ref) => new AuthNotifier());
auth_repository.dart
class AuthRepository{
static String url = "http://10.0.2.2:8000/api/";
final Dio _dio = Dio();
Future<bool> login(data) async {
try {
Response response = await _dio.post(url+'sanctum/token',data:json.encode(data));
return true;
} catch (error) {
return false;
}
}
}
login_screen.dart
void login() async{
if(formKey.currentState.validate()){
setState((){this.isLoading = true;});
var data = {
'email':this.email,
'password':this.password,
'device_name':'mobile_phone'
};
var result = await AuthRepository().login(data);
if(result){
context.read(authProvider).isLogin(true);
setState((){this.isLoading = false;});
}else
setState((){this.isLoading = false;});
}
}
Since I'm not coming from mobile background and just recently use flutter+riverpod in my recent project, I cannot say this is the best practice. But there are some points I'd like to note:
Use interface such IAuthRepository for repository. Riverpod can act as a dependency injection.
final authRepository = Provider<IAuthRepository>((ref) => AuthRepository());
Build data to send in repository. You should separate presentation, business logic, and explicit implementation for external resource if possible.
Future<bool> login(String email, String password) async {
try {
var data = {
'email': email,
'password': password,
'device_name':'mobile_phone'
};
Response response = await _dio.post(url+'sanctum/token',data:json.encode(data));
return true;
} catch (error) {
return false;
}
}
Do not call repository directly from presentation/screen. You can use the provider for your logic, which call the repository
class AuthNotifier extends StateNotifier<Auth>{
final ProviderReference ref;
IAuthRepository _authRepository;
AuthNotifier(this.ref) : super(Auth(false)) {
_authRepository = ref.watch(authRepository);
}
Future<void> login(String email, String password) async {
final loginResult = await_authRepository.login(email, password);
state = Auth(loginResult);
}
}
final authProvider = StateNotifierProvider((ref) => new AuthNotifier(ref));
On screen, you can call provider's login method
login() {
context.read(authProvider).login(this.email, this.password);
}
Use Consumer or ConsumerWidget to watch the state and decide what to build.
It also helps that instead of Auth with isLogin for the state, you can create some other state. At the very least, I usually create an abstract BaseAuthState, which derives to AuthInitialState, AuthLoadingState, AuthLoginState, AuthErrorState, etc.
class AuthNotifier extends StateNotifier<BaseAuthState>{
...
AuthNotifier(this.ref) : super(AuthInitialState()) { ... }
...
}
Consumer(builder: (context, watch, child) {
final state = watch(authProvider.state);
if (state is AuthLoginState) ...
else if (state is AuthLoadingState) ...
...
})
Instead of using a bool, I like to use enums or class for auth state
enum AuthState { initialize, authenticated, unauthenticated }
and for login state
enum LoginStatus { initialize, loading, success, failed }
I make one file to shared preferences to store data in it from my app. It's work fine.But now I want to delete data from store as button log-out for user. So if user click button of log-out data will be clear from shared preferences file. How I can do it from different class?
import 'package:shared_preferences/shared_preferences.dart';
class MyPreferences{
static const USER = "user";
static const PASSWORD = "password";
static final MyPreferences instance = MyPreferences._internal();
//Campos a manejar
SharedPreferences _sharedPreferences;
String user = "";
String password = "";
MyPreferences._internal(){
}
factory MyPreferences()=>instance;
Future<SharedPreferences> get preferences async{
if(_sharedPreferences != null){
return _sharedPreferences;
}else{
_sharedPreferences = await SharedPreferences.getInstance();
user = _sharedPreferences.getString(USER);
password = _sharedPreferences.getString(PASSWORD);
return _sharedPreferences;
}
}
Future<bool> commit() async {
await _sharedPreferences.setString(USER, user);
await _sharedPreferences.setString(PASSWORD, password);
}
Future<MyPreferences> init() async{
_sharedPreferences = await preferences;
return this;
}
}
Define your shared preference manager class as a singleton as given,
class SharedPreferenceManager{
static final SharedPreferenceManager _singleton = new SharedPreferenceManager._internal();
factory SharedPreferenceManager() {
return _singleton;
}
SharedPreferenceManager._internal() {
... // initialization logic here
}
... // rest of the class
}
By this, you can create and access the single, reusable instance of that class. You can define a static method in the class which will be accessible from outside. As the static method can have access to only static data members, You should define the sharedPrefernece member variable as static. Here is how you can clear all the data.
static Future<bool> clearSharedPrefs(){
SharedPreferences preferences = await SharedPreferences.getInstance();
await preferences.clear();
}
After this, you'll be able to call this method from any class, just as SharedPreferenceManager.clearSharedPrefs().
It's a good practice to follow the singleton pattern for database, network and shared preference related tasks.
Here is the code you should go with.
import 'package:shared_preferences/shared_preferences.dart';
class MyPreferences{
static const USER = "user";
static const PASSWORD = "password";
static final MyPreferences instance = MyPreferences._internal();
static SharedPreferences _sharedPreferences;
String user = "";
String password = "";
MyPreferences._internal(){}
factory MyPreferences()=>instance;
Future<SharedPreferences> get preferences async{
if(_sharedPreferences != null){
return _sharedPreferences;
}else{
_sharedPreferences = await SharedPreferences.getInstance();
user = _sharedPreferences.getString(USER);
password = _sharedPreferences.getString(PASSWORD);
return _sharedPreferences;
}
}
Future<bool> commit() async {
await _sharedPreferences.setString(USER, user);
await _sharedPreferences.setString(PASSWORD, password);
}
Future<MyPreferences> init() async{
_sharedPreferences = await preferences;
return this;
}
static Future<bool> clearPreference() async{
if(_sharedPreferences){
_sharedPreferences.clear();
}
}
}
You can use remove or clear on shared preferences.
SharedPreferences preferences = await SharedPreferences.getInstance();
preferences.clear();
// OR
preferences.remove("MY KEY HERE");
Coming from Object Oriented Programming Background, I planned on making a dedicated Settings Class to store certain basic data about the app.
I planned on starting with saving the theme of the application using SharedPreferences and LocalStorage.
However, SharedPreferences.getInstance() always seems to be returning null.
I have tried simply running, running in Debug mode, having a separate async method to load the SharedPreferences and returning a Future which is unwrapped using .then(). I can't seem to figure out why I am always getting null from SharedPreferences.getInstance() in the AppSettings.getInstance() method that I have written.
import 'package:shared_preferences/shared_preferences.dart';
import 'package:localstorage/localstorage.dart';
import 'package:flutter/material.dart';
class AppSettings {
// Singleton Instance
static AppSettings _appSettings;
// For First Launch Recognition
bool _initialize;
// Storage instances for persistent settings storage
static SharedPreferences _prefs;
static LocalStorage _dayColors = new LocalStorage('_dayColors');
static LocalStorage _nightColors = new LocalStorage('_nightColors');
// App Settings
bool _nightTheme;
Color _dayBgColor;
Color _primaryDayColor;
Color _secondaryDayColor;
Color _accentDayColor;
Color _nightBgColor;
Color _primaryNightColor;
Color _secondaryNightColor;
Color _accentNightColor;
static AppSettings getInstance() {
SharedPreferences.getInstance().then((prefs) => _prefs = prefs);
_appSettings ??= AppSettings._();
return _appSettings;
}
///
/// Initialize App Settings
///
AppSettings._() {
_checkIfFirstLaunch();
if (_initialize) {
_loadDefaultSettings();
_saveSettings();
} else {
_loadSettings();
}
}
_checkIfFirstLaunch() {
try {
_initialize = _prefs.getBool("_initialize");
} catch (e) {
_initialize = true;
}
}
_loadSettings() {
_nightTheme = _prefs.getBool("_nightTheme");
_dayColors.ready.then((_) => _loadDayColors());
_nightColors.ready.then((_) => _loadNightColors());
}
_loadDefaultSettings() {
_nightTheme = false;
_dayBgColor = Colors.white;
_primaryDayColor = Colors.blue;
_secondaryDayColor = Colors.lightBlue;
_accentDayColor = Colors.blueAccent;
_nightBgColor = Colors.black54;
_primaryNightColor = Colors.green;
_secondaryNightColor = Colors.lightGreen;
_accentNightColor = Colors.amber;
}
_saveSettings() {
_prefs.setBool("_nightTheme", _nightTheme);
_dayColors.ready.then((_) => _saveDayColors());
_nightColors.ready.then((_) => _saveNightColors());
}
}
SharedPreferences.getInstance() should return SharedPreferences singleton instance. It keeps returning null.
Your function is async and your callback (then) executes after of the return of getInstance(). You must change your function to use await and get the value of SharedPreferences.getInstance() instead use SharedPreferences.getInstance().then(...)
Look the documentation: https://pub.dev/documentation/shared_preferences/latest/shared_preferences/SharedPreferences/getInstance.html
Implementation of SharedPreferences.getInstance().
static Future<SharedPreferences> getInstance() async {
if (_instance == null) {
final Map<String, Object> preferencesMap =
await _getSharedPreferencesMap();
_instance = SharedPreferences._(preferencesMap);
}
return _instance;
}
Here is the code that worked based on Augusto's answer:
static Future<AppSettings> getInstance() async {
_prefs = await SharedPreferences.getInstance();
_appSettings ??= AppSettings._();
return _appSettings;
}