I'm trying to navigate to a screen where depending on 3 factors:
If the app has run before or not
If the user is null or not
If the email is verified or not.
import 'package:client/providers/auth_provider.dart';
import 'package:flutter/material.dart';
import 'package:firebase_auth/firebase_auth.dart';
import 'package:provider/provider.dart';
import 'package:shared_preferences/shared_preferences.dart';
import '../screens/home_screen.dart';
import '../screens/login_screen.dart';
class Wrapper extends StatefulWidget {
#override
_WrapperState createState() => _WrapperState();
}
class _WrapperState extends State<Wrapper> {
FirebaseAuth auth = FirebaseAuth.instance;
#override
void initState() {
super.initState();
}
#override
Widget build(BuildContext ctx) {
return FutureBuilder(
future: hasAlreadyStarted(),
builder: (ctx, snapshot) {
return Provider.of<User>(ctx) != null &&
snapshot.data == true &&
AuthProvider().isEmailVerified
? HomeScreen()
: LoginScreen();
});
}
Future<bool> hasAlreadyStarted() async {
SharedPreferences prefs = await SharedPreferences.getInstance();
try {
if (prefs.getBool("hasRun") == null) {
await AuthProvider().logout();
setState(() {
prefs.setBool("hasRun", true);
});
return true;
} else {
return true;
}
} catch (error) {
setState(() {
prefs.setBool("hasRun", null);
});
return false;
}
}
}
The screen works fine on it's own, but when i Navigate from a different screen it gives me the error.
Could not find the correct Provider<User> above this FutureBuilder<bool> Widget
Can you explain the error and give me a solution. Thanks :D
I just needed to wrap the entire MaterialApp with the StreamProvider
Related
appreciate the help! I've looked through some of the other responses on here and I can't find an answer.
I have a Provider, in which I have an async function defined. It reaches out to an external API, gets data, and then is meant to update the attributes in the Provider with the data received.
The Widget that uses the provider is meant to build a ListView with that data. projects is null until the response is received. That's why I need the async await functionality to work here. The error I'm getting says that "length can't be called on null", which means projects is still null at the time is reaches that line. That is because the async functionality isn't working.
Here is the Provider, in which my async function is defined:
import 'package:flutter/material.dart';
import 'package:http/http.dart' as http;
import 'dart:convert';
import '../../constants/urls.dart';
import 'project.dart';
class Projects with ChangeNotifier{
List<Project> _projects;
List<Project> _myProjects;
final String authToken;
final List<Project> previousProjects;
final bool _initialLoad = true;
Projects(this.authToken, this.previousProjects);
List<Project> get projects {
return _projects;
}
List<Project> get myProjects {
return _myProjects;
}
bool get initialLoad {
return _initialLoad;
}
Future<void> fetchProjects() async {
print('inside future, a');
try {
var response = await http.get(
Uri.parse(Constants.fetchProjectsURL),
headers: {"Authorization": "Bearer " + authToken},
);
print('inside future, b');
if (response.statusCode == 200) {
final extractedData = json.decode(response.body) as List;
final List<Project> tempLoadedProjects = [];
extractedData.forEach((project) {
tempLoadedProjects.add(
Project(
// insert project params
),
);
});
_projects = tempLoadedProjects;
print(_projects);
print(projects);
notifyListeners();
} else {
print('something happened');
}
} catch (error) {
throw error;
}
}
}
Then, I used this provider in the following Widget:
import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import '../../../providers/projects/projects_provider.dart';
class ProjectsColumn extends StatelessWidget {
Future<void> fetchProjects(ctx) async {
await Provider.of<Projects>(ctx).fetchProjects();
}
Widget build(BuildContext context) {
print('Before fetch');
fetchProjects(context);
print('After fetch');
final projects = Provider.of<Projects>(context, listen: false).projects;
return ListView.builder(
itemCount: projects.length,
itemBuilder: (BuildContext ctx, int index) {
return Card(
child: Text(
'Project Name:${projects[index]}',
),
);
});
}
}
Thoughts?
You need to put await before the method to a wait, but you can't do this in build() method, So you can use future builder like the answer of #jamesdlin
or you can call fetchProjects method in intState first like this way:
class ProjectsColumn extends StatefulWidget {
#override
State<ProjectsColumn> createState() => _ProjectsColumnState();
}
class _ProjectsColumnState extends State<ProjectsColumn> {
bool _isLoading = true;
Future<void> _fetchProjects() async {
await Provider.of<Projects>(context, listen: false).fetchProjects();
_isLoading = false;
if (mounted) setState(() {});
}
#override
void initState() {
super.initState();
_fetchProjects();
}
#override
Widget build(BuildContext context) {
return _isLoading
? const Center(child: CircularProgressIndicator())
: Consumer<Projects>(
builder: (context, builder, child) => builder.projects.isEmpty
? const Center(child: Text('No Projects Found'))
: ListView.builder(
shrinkWrap: true,
itemCount: builder.projects.length,
itemBuilder: (BuildContext ctx, int index) {
return Card(
child: Text(
'Project Name:${builder.projects[index]}',
),
);
},
),
);
}
}
EDIT:
a) From the docs HERE BuildContext objects are passed to WidgetBuilder functions (such as StatelessWidget.build), and are available from the State.context member., and in the previous example I used StatefulWidget widget that extends state class, then you can use context outside build but inside the class extends state, not like StatelessWidget.
b) mounted condition, it represents whether a state is currently in the widget tree, i used it to prevent the famous error: setState() called after dispose()
see docs HERE, also this useful answer HERE
Firebase Auth is working properly, I'm able to log in, Sign in but I want to preserve the state of the application. For state persistence, I'm using Share preferences.
I'm using sharedpreferences. I made a class and defined some keys and methods to fetch and set the data in the keys at the time of login and use it later in the app.
Please help me out with an easy approch how to do this.
import 'package:flutter/material.dart';
import 'package:shared_preferences/shared_preferences.dart';
class CurrentUser {
static SharedPreferences? mypreferences;
static const emailKey = 'emailKey';
static const passwordKey = 'paswordKey';
static const loginStatusKey = 'loginStatusKey';
static Future init() async {
mypreferences = await SharedPreferences.getInstance();
}
static Future setUserEmail(String? emailValue) async {
return await mypreferences?.setString(emailKey, emailValue!);
}
static Future setUserPassword(String? passwordValue) async {
return await mypreferences?.setString(passwordKey, passwordValue!);
}
static Future setLoginStatus(bool status) async {
return await mypreferences?.setBool(loginStatusKey, status);
}
static String? getUserEmail() {
return mypreferences?.getString(emailKey);
}
static String? getUserPassword() {
return mypreferences?.getString(passwordKey);
}
static bool? getUserLoginStatus(){
if(loginStatusKey==null){
mypreferences?.setBool(loginStatusKey, false);
}
return mypreferences?.getBool(loginStatusKey);
}
}```
// storing the value during login //
``` myLogIn() async {
try {
UserCredential myuser= await FirebaseAuth.instance
.signInWithEmailAndPassword(email: email, password: password);
// print(myuser);
// print(myuser.user?.email);
CurrentUser.setUserEmail(myuser.user?.email);
CurrentUser.setUserPassword(password);
CurrentUser.setLoginStatus(true);
Navigator.pushReplacementNamed(context, MyRoutes.homeRoute);
} on FirebaseAuthException catch (e) {
if (e.code == 'user-not-found') {
print('user is not registered');
ScaffoldMessenger.of(context).showSnackBar(
MySnackBar.showcustomSnackbar('user is not registered'));
} else if (e.code == 'wrong-password') {
print('wrong password');
ScaffoldMessenger.of(context)
.showSnackBar(MySnackBar.showcustomSnackbar('wrong password'));
}
}
}```
// using the store login status in main file to show login page and home page accordingly.
```import 'package:flutter/material.dart';
import 'package:firebase_core/firebase_core.dart';
// import 'firebase_options.dart';
import './pages/login.dart';
import './pages/signup.dart';
import './pages/homepage.dart';
import './utils/my_theme.dart';
import './utils/my_routes.dart';
import './pages/forgot_password.dart';
import './utils/my_user.dart';
void main() {
WidgetsFlutterBinding.ensureInitialized();
CurrentUser.init();
runApp(MyApp());
}
class MyApp extends StatefulWidget {
#override
State<MyApp> createState() => _MyAppState();
}
class _MyAppState extends State<MyApp> {
// const MyApp({ Key? key }) : super(key: key);
final Future<FirebaseApp> initializeMyFirebaseApp = Firebase.initializeApp();
bool? isLogin = CurrentUser.getUserLoginStatus();
#override
void initState() {
// TODO: implement initState
isLogin = CurrentUser.getUserLoginStatus();
super.initState();
}
#override
Widget build(BuildContext context) {
return FutureBuilder(
future: initializeMyFirebaseApp,
builder: (context, snaphot) {
//Error checking
if (snaphot.hasError) {
print("Something went wrong!");
}
//If snapshot state is in waiting or so
if (snaphot.connectionState == ConnectionState.waiting) {
return Center(
child: CircularProgressIndicator(),
);
}
//else we will show the normal login page.
return MaterialApp(
theme: MyTheme.lightTheme(context),
//isUserLoggedIn !=null ? isUserLoggedIn ? Home() : SignUp() : SignIn(),
home:isLogin!=null ?
isLogin! ? HomePage() : Login() : Login(),
// Login(),
routes: {
// "/":(context) => Login(),
MyRoutes.loginRoute: (context) => Login(),
MyRoutes.signupRoute: (context) => SignUp(),
MyRoutes.homeRoute: (context) => HomePage(),
MyRoutes.forgotpasswordRoute: (context) => ForgotPassword(),
},
);
});
}
}
```
I'm create a project on Flutter. And I'm using a provider to change screens in my app.
Here is my main.dart file:
import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import 'package:school_app/services/auth_service.dart';
import 'package:school_app/wrapper.dart';
void main() async {
WidgetsFlutterBinding.ensureInitialized();
runApp(MyApp());
}
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return ChangeNotifierProvider(
create: (_) => AuthService().auth,
child: MaterialApp(
home: Wrapper(),
),
);
}
}
Also this is my wrapper.dart file where the screens choose:
import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import 'package:school_app/screens/authenticate/auth.dart';
import 'package:school_app/models/user.dart';
import 'package:school_app/screens/school/home.dart';
import 'package:school_app/services/auth_service.dart';
class Wrapper extends StatelessWidget {
#override
Widget build(BuildContext context) {
final user = Provider.of<AuthProvider>(context);
print(user.auth);
if(!user.auth) return Auth();
return Home();
}
}
And it is my AuthProvider class:
import 'package:dio/dio.dart';
import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import 'package:shared_preferences/shared_preferences.dart';
class AuthService {
/* AuthUser _user(User user) {
return user != null ? AuthUser(uid: user.uid) : null;
}*/
AuthProvider auth = new AuthProvider();
//sign in
Future signIn(String username, String password) async {
try {
SharedPreferences prefs = await SharedPreferences.getInstance();
var dio = Dio();
Response user = await dio.post('url', data: {
'username': username,
'password': password
});
if(user.data['success'] == false) return user.data['msg'];
await prefs.setString('token', user.data['token']);
auth.setAuth(true);
print("SUCCESS");
} catch(e) {
print('Error ' + e.toString());
}
}
}
class AuthProvider with ChangeNotifier {
bool _auth;
AuthProvider() {
_auth = false;
}
bool get auth => _auth;
void setAuth(bool auth) {
_auth = auth;
notifyListeners();
}
}
And when I call a function in AuthProvider class setAuth, nothing changed. Can you help me and find my mistake?
EDIT
I'm making all changes that you writes but it is not working. Here is my main.dart:
import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import 'package:school_app/services/auth_service.dart';
import 'package:school_app/wrapper.dart';
void main() async {
WidgetsFlutterBinding.ensureInitialized();
runApp(MyApp());
}
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return ChangeNotifierProvider(
create: (_) => AuthProvider(),
child: MaterialApp(
home: Wrapper(),
),
);
}
}
Also wrapper.dart:
import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import 'package:school_app/screens/authenticate/auth.dart';
import 'package:school_app/screens/school/home.dart';
import 'package:school_app/services/auth_service.dart';
class Wrapper extends StatefulWidget {
#override
_WrapperState createState() => _WrapperState();
}
class _WrapperState extends State<Wrapper> {
#override
void initState() {
// TODO: implement initState
super.initState();
AuthService().auth;
}
#override
Widget build(BuildContext context) {
return Consumer<AuthProvider>(builder: (context, authProvider, child) {
print(authProvider.auth);
if (!authProvider.auth) {
return Auth();
} else {
return Home();
}
});
}
}
And AuthService and AuthProvider classes:
import 'package:dio/dio.dart';
import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import 'package:shared_preferences/shared_preferences.dart';
class AuthService {
/* AuthUser _user(User user) {
return user != null ? AuthUser(uid: user.uid) : null;
}*/
AuthProvider auth = new AuthProvider();
//sign in
Future signIn(String username, String password) async {
try {
SharedPreferences prefs = await SharedPreferences.getInstance();
var dio = Dio();
Response user = await dio.post('url', data: {
'username': username,
'password': password
});
if(user.data['success'] == false) return user.data['msg'];
await prefs.setString('token', user.data['token']);
auth.setAuth(true);
print("SUCCESS");
} catch(e) {
print('Error ' + e.toString());
}
}
}
class AuthProvider with ChangeNotifier {
bool _auth;
AuthProvider() {
_auth = false;
}
bool get auth => _auth;
void setAuth(bool auth) {
_auth = auth;
notifyListeners();
}
}
Notice, that here two classes and in AuthService I'm calling function .setAuth(true).
In your current implementation of Wrapper, you are rendering the widget once and not listening to whether the values changed. You could use Consumer as suggested above. You could also choose to watch the value for changes - like this:
class Wrapper extends StatelessWidget {
#override
Widget build(BuildContext context) {
final user = context.watch<AuthProvider>();
print(user.auth);
if(!user.auth) return Auth();
return Home();
}
}
When you use a watch or Consumer pattern, the widget will be rendered when the values of the underlying store (which is AuthProvider here) gets changed.
The only missing part here is that you never Consume the AuthProvider to listen to the notifyListeners() trigger.
The correct implementation looks like the following (I didn't try it, you may have to correct some typo errors, but you'll get the idea !)
class Wrapper extends StatelessWidget {
#override
Widget build(BuildContext context) {
return Consumer<AuthProvider>(
builder: (context, authProvider, child) {
if (!authProvider.auth) {
return Auth();
} else {
return Home();
}
}
);
}
}
EDIT
I didn't notice you weren't injecting the right Class in your ChangeNotifierProvider. You'll also have to update your widget MyApp
#override
Widget build(BuildContext context) {
return ChangeNotifierProvider(
create: (_) => AuthProvider(),
child: MaterialApp(
home: Wrapper(),
),
);
}
And in this case you probably should transform your Wrapper widget to a Stateful widget, and in the initState method you should call AuthService().auth.
I strongly recommend you to read the official documentation of Provider, looks like things aren't crystal clear yet in your mind
EDIT 2
You're still missing the point of the Provider library.
The goal of this lib is to provide an instance of a class to your widget tree so you don't have to re-create an instance in each widget.
Here, in AuthService class you're re-creating a AuthProvider with AuthProvider auth = new AuthProvider(); instead of referring to the existing instance created in the parent Widget.
To refer to a previously created instance, you should use Provider.of<AuthProvider>(context); in the AuthService class, or, even better, pass the instance of AuthProvider as a parameter in the signIn method.
Recently I am developing first ever app in Flutter and I know the basics only.
So here's the problem which I am facing currently.
I have to Navigate One of the two screens, either Register or Home page according to old/new user, So what I did is here.
import 'package:flutter/material.dart';
import 'package:shared_preferences/shared_preferences.dart';
import 'Register.dart';
import 'HomePage.dart';
class Authenticate extends StatefulWidget {
#override
_AuthenticateState createState() => _AuthenticateState();
}
class _AuthenticateState extends State<Authenticate> {
String _userName = "";
#override
void initState() {
super.initState();
_getUserName();
}
_getUserName() async {
SharedPreferences pref = await SharedPreferences.getInstance();
setState(() {
_userName = pref.getString('userName') ?? "";
});
}
Widget build(BuildContext context) {
if (_userName == "") {
print('name : $_userName , NEW user'); // ERROR - why it's printing on console for old User ?
return Register();
} else {
return HomePage(_userName);
}
}
}
So the problem is, even if I am opening app through old user, it is printing the debug code written for new user and there's around 0.3 sec screen visibility of Register screen.
So what should I do to fix this?
The print is happening because this line of code:
SharedPreferences pref = await SharedPreferences.getInstance();
is asynchronous, which means that it might invoke in some later point in time. Because of that the build method is called first, then your _getUserName method finished, which causes a setState and invokes a build method again.
You might want to show some kind of loader screen until sharedPrefernces is initialized and then decide wheter to show Register or Home page.
Example code:
class _AuthenticateState extends State<Authenticate> {
String _userName = "";
bool _isLoading = true;
#override
void initState() {
super.initState();
_getUserName();
}
_getUserName() async {
SharedPreferences pref = await SharedPreferences.getInstance();
setState(() {
_userName = pref.getString('userName') ?? "";
_isLoading = false;
});
}
Widget build(BuildContext context) {
if (_isLoading) {
return Center(child: CupertinoActivityIndicator());
} else if (_userName == "") {
print('name : $_userName , NEW user'); // ERROR - why it's printing on console for old User ?
return Register();
} else {
return HomePage(_userName);
}
}
}
Try this:
class _AuthenticateState extends State<Authenticate> {
String _userName;
#override
void initState() {
super.initState();
_getUserName();
}
_getUserName() async {
SharedPreferences pref = await SharedPreferences.getInstance();
setState(() {
_userName = pref.getString('userName') ?? '';
});
}
Widget build(BuildContext context) {
if (_userName == null) {
return Center(child: CircularProgressIndicator());
} else if (_userName == '') {
print('name : $_userName , NEW user');
return Register();
} else {
return HomePage(_userName);
}
}
}
In this case, _userName is null initially and will only be assigned a value after the _getUserName() returns either an empty String or an old userName. When null, the widget will build a progress indicator instead. If you don't want that, just return a Container().
When using shared_preferences on flutter in main.dart in order to change the initialRoute depending on if user have seen the first page or if user is logged in I am getting the boolean which is created throughout the app and added to shared_preferences, every time I start app, I get the initialRoute string correct when debugging, but I still end up getting on the first page, regardless the conditions.
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:provider/provider.dart';
import 'package:shared_preferences/shared_preferences.dart';
import 'dart:developer';
import './pages/registration.dart';
import './pages/login_page.dart';
import './pages/confirmation.dart';
import './pages/lang_page.dart';
import './pages/main_page.dart';
import './pages/user_data.dart';
import './provider/provider.dart';
void main() => runApp(CallInfoApp());
class CallInfoApp extends StatefulWidget {
#override
_CallInfoAppState createState() => _CallInfoAppState();
}
class _CallInfoAppState extends State<CallInfoApp> {
SharedPreferences prefs;
void getSPInstance() async {
prefs = await SharedPreferences.getInstance();
}
dynamic langChosen;
dynamic isLoggedIn;
String initialRoute;
void dataGetter() async {
await getSPInstance();
setState(() {
langChosen = prefs.getBool('langChosen');
// print(langChosen);
isLoggedIn = prefs.getBool('isLoggedIn');
});
}
void getRoute() async {
await dataGetter();
debugger();
if (langChosen == true && isLoggedIn != true) {
setState(() {
initialRoute = '/login_page';
});
} else if (isLoggedIn == true) {
initialRoute = '/main_page';
} else {
setState(() {
initialRoute = '/';
});
}
}
#override
void initState() {
super.initState();
debugger();
getRoute();
}
#override
Widget build(BuildContext context) {
SystemChrome.setPreferredOrientations([
DeviceOrientation.portraitUp,
DeviceOrientation.portraitDown,
]);
return ChangeNotifierProvider<AppData>(
create: (context) => AppData(),
child: MaterialApp(
title: 'Call-INFO',
theme: ThemeData(
primarySwatch: Colors.blue,
),
initialRoute: initialRoute,
routes: {
'/': (context) => LanguagePage(),
'/registration_page': (context) => RegistrationPage(),
'/login_page': (context) => LoginPage(),
'/confirmation_page': (context) => ConfirmationPage(),
'/user_data_page': (context) => UserDataPage(),
'/main_page': (context) => MainPage(),
},
),
);
}
}
Since SharedPreference.getInstance() is an async function it will need some time until the instance is available. If you want to use it for initial route you have to make your main function async and preload it there before your MaterialApp is build.
SharedPreference prefs; //make global variable, not best practice
void main() async {
prefs = await SharedPreference.getInstance();
runApp(CallInfoApp());
}
And remove getSPInstance() from dataGetter
Also keep in midn that prefs.getBool('langChosen') will return null and not false if no entry is made into shared preference so use
langChosen = prefs.getBool('langChosen')??false;
isLoggedIn = prefs.getBool('isLoggedIn')??false;
While this solution will work it's not really good practice. I would recommend to have the initialRoute fixed to a splash screen and handle forwarding to the right page from there. A simple splash screen could look like that:
class SplashScreen extends StatefulWidget {
#override
_SplashScreenState createState() => _SplashScreenState();
}
class _SplashScreenState extends State<SplashScreen> {
#override
Widget build(BuildContext context) {
return Scaffold(body: Center(child: CircularProgressIndicator()));
}
#override
void initState() {
initSplash();
super.initState();
}
Future<void> initSplash() async {
final prefs = await SharedPreferences.getInstance();
final langChosen = prefs.getBool("lang_chosen") ?? false;
final isLoggedIn = prefs.getBool("logged_in") ?? false;
if (langChosen == true && isLoggedIn != true) {
Navigator.of(context).pushReplacementNamed('/login_page');
} else if (isLoggedIn == true) {
Navigator.of(context).pushReplacementNamed('/main_page');
} else {
Navigator.of(context).pushReplacementNamed('/');
}
}
}
Use initState to derive the data your logic is based on (i.e. fetching shared pref info). And use await keyword so that program will wait until the data is fetched from SharedPrefs. Adding the following code to class _CallInfoAppState should help
#override
void initState() {
super.initState();
dataGetter();
}
void dataGetter() async {
await getSPInstance();
setState(() {
langChosen = prefs.getBool('langChosen');
isLoggedIn = prefs.getBool('isLoggedIn');
});
}