I have a problem like this :
In Splash Page , i check in sharedpreference to get saved token when login successfully .If i have token , i request Api to get account information and move to next page like this:
Future check() async {
String _getToken = await splashBloc.getTokenFormSharedPref();
if (_getToken=='0') {
Navigator.of(context).pushReplacement(
MaterialPageRoute(builder: (context) => LoginMain()));
} else {
splashBloc.getAccountInfo();
Navigator.of(context).pushReplacement(
MaterialPageRoute(builder: (context) => HomeScreenMain()));
}
}
and this is BLoC class:
class SplashBloc extends BlocBase{
String _getToken = '';
Future<String> getTokenFormSharedPref() async{
SharedPreferences prefs = await SharedPreferences.getInstance();
_getToken = (prefs.getString('token') ?? '0');
return _getToken;
}
final accountInfoController = new StreamController<Account>();
Sink<Account> get accountInfoSink => accountInfoController.sink;
Stream<Account> get accountInfoStream => accountInfoController.stream;
Future getAccountInfo() async{
Account account = await NetworkService().getAccountInfo2(_getToken);
accountInfoSink.add(account);
print('from splash: '+account.fullName);
}
#override
void dispose() {
accountInfoController.close();
}
}
When i check log , it totally request successfully and the problem is how can i acesss data in streambuilder in next page that is HomeScreenMain()?
Thanks for help!!
You can declare a variable in HomeScreenMain() and send the data you received before to the class constructor like this:
HomeScreenMain() {
final data;
HomeScreenMain(this.data)
//....
}
and when you want to call this widget you can pass that data from block to this widget
You appear to use a very basic approach with BLoC. Not sure if my answer helps there.
But if you use the library flutter_bloc, then you can use on the next page
ˋfinal bloc = context.read;
This looks for a provider of this bloc type upstream in the Widget tree and assigns it to ˋbloc
Related
I'm learning Riverpod provider and stuck on a topic regarding passing values between screens.
As I learnt from Riverpod docs - it delivers a provider that enables values to be accessed globally... and here is my case.
I'm creating a service repo, that contains some methods delivering futures (e.g. network request to verify user):
class VerifyUser {
Future<User> verifyUser(String input) async {
await Future.delayed(const Duration(seconds: 2));
print(input);
if (input == 'Foo') {
print('Foo is fine - VERIFIED');
return User(userVerified: true);
} else {
print('$input is wrong - NOT VERIFIED');
return User(userVerified: false);
}
}
}
Next step is to create providers - I'm using Riverpod autogenerate providers for this, so here are my providers:
part 'providers.g.dart';
#riverpod
VerifyUser verifyUserRepo(VerifyUserRepoRef ref) {
return VerifyUser();
}
#riverpod
Future<User> user(
UserRef ref,
String input
) {
return ref
.watch(verifyUserRepoProvider)
.verifyUser(input);
}
and there is a simple User model for this:
class User {
bool userVerified;
User({required this.userVerified});
}
I'm creating a wrapper, that should take the user to Homescreen, when a user is verified, or take the user to authenticate screen when a user is not verified.
class Wrapper extends ConsumerWidget {
#override
Widget build(BuildContext context, WidgetRef ref) {
String user = '';
final userFromProvider = ref.watch(userProvider(user));
if (user == 'verified') {
print(userFromProvider);
return MyHomePage();
} else {
return Authenticate();
}
}
}
App opens on Authenticate screen because there is no info about the user.
On Authenticate screen I'm getting input and passing it to FutureProvider for verification.
final vUser = ref.watch(userProvider(userInput.value.text));
When I'm pushing to Wrapper and calling provider - I'm not getting the value I initially got from future.
ElevatedButton(
onPressed: () async {
vUser;
if (vUser.value?.userVerified == true) {
print('going2wrapper');
Navigator.of(context).push(MaterialPageRoute(builder: (context) => Wrapper()));
}},
child: const Text('Verify User'))
Inside Wrapper it seems that this is only thing that I can do:
String user = '';
final userFromProvider = ref.watch(userProvider(user));
But it makes me call the provider with a new value... and causing unsuccessful verification and I cannot proceed to homescreen.
As a workaround, I see that I can pass the named argument to Wrapper, but I want to use the provider for it... is it possible?
I hope that there is a solution to this.
Thx!
David
I'm creating an app with firebase as a database. After sending data to firebase, app screen should pop out for that I had bloclistener on the screen but after sending the data to firestore database, nothing is happening, flow is stopped after coming to loaded state in bloc file why? check my code so that you will know. I can see my data in firebase but it is not popping out because flow is not coming to listener.
state:
class SampletestInitial extends SampletestState {
#override
List<Object> get props => [];
}
class SampletestLoaded extends SampletestState {
SampletestLoaded();
#override
List<Object> get props => [];
}
class SampletestError extends SampletestState {
final error;
SampletestError({required this.error});
#override
List<Object> get props => [error];
}
bloc:
class SampletestBloc extends Bloc<SampletestEvent, SampletestState> {
SampletestBloc() : super(SampletestInitial()) {
on<SampletestPostData>((event, emit) async {
emit(SampletestInitial());
try {
await Repo().sampleTesting(event.des);
emit(SampletestLoaded());
} catch (e) {
emit(SampletestError(error: e.toString()));
print(e);
}
});
}
}
Repo: ---- Firebase post data
Future<void> sampleTesting(String des) async {
final docTicket = FirebaseFirestore.instance.collection('sample').doc();
final json = {'Same': des};
await docTicket.set(json);
}
TicketScreen:
//After clicking the button ---
BlocProvider<SampletestBloc>.value(
value: BlocProvider.of<SampletestBloc>(context, listen: false)
..add(SampletestPostData(description.text)),
child: BlocListener<SampletestBloc, SampletestState>(
listener: (context, state) {
if (state is SampletestLoaded) {
Navigator.pop(context);
print("Popped out");
}
},
),
);
im not sure but i think that you have the same hash of:
AllData? data;
try to remove AllData? data; and create new data variable so you can be sure that you has a new hash code every time you call createTicket method;
final AllData data = await repo.createTicket(AllData(
Check your AllData class properties.
BLoC will not show a new state if it not unique.
You need to check whether all fields of the AllData class are specified in the props field.
And check your BlocProvider. For what you set listen: false ?
BlocProvider.of<SampletestBloc>(context, listen: false)
I want to implement Auto Login with Shared preferences.
What I want to implement is that as soon as 'LoginPage' starts, it goes to the next page without rendering LoginPage according to the Flag value stored in Shared preferences.
However, there is a problem in not becoming Navigate even though implementing these functions and calling them from initstate. What is the problem?
//Login Page
void autoLogIn() async {
final SharedPreferences prefs = await SharedPreferences.getInstance();
final String userId = prefs.getString('username');
print("ddddddddddddddd");
SocketProvider provider = Provider.of<SocketProvider>(context);
Future.delayed(Duration(milliseconds: 100)).then((_) {**//I tried giving Delay but it still didn't work.**
Navigator.of(context).pushNamedAndRemoveUntil("/MainPage", (route) => false);
});
}
#override
void initState() {
// TODO: implement initState
loginBloc = BlocProvider.of<LoginBloc>(context);
if(!kReleaseMode){
_idController.text = "TESTTEST";
_passwordController.text = "1234123";
}
initBadgeList();
autoLogIn();**//This is the function in question.**
super.initState();
print("1111111111111111");
}
I don't think you should show LoginPage widget if user is already logged in and then navigate to main page.
I suggest you to use FutureBuilder and show either splash screen or loader while performing await SharedPreferences.getInstance(). In this case your App widget should look like this:
class App extends MaterialApp {
App()
: super(
title: 'MyApp',
...
home: FutureBuilder(
future: SharedPreferences.getInstance(),
builder: (context, snapshot) {
if (snapshot.data != null) {
final SharedPreferences prefs = snapshot.data;
final userId = prefs.getString('username');
...
return userId == null ?? LoginPage() : MainPage();
} else {
return SplashScreenOrLoader();
}
}));
}
But if you still want to show LoginPage first, just replace SplashScreenOrLoader() with LoginPage() in code above.
I am trying to navigate to a screen from a future method. However I get an error saying undefined name context. I tried navigating from Widget build but the parameter is created within this method and I need it for navigating. I've been stuck on this for a very long time. Any help will be really appreciated.
Future<void> addBookingConversation(Booking booking) async {
Conversation conversation = Conversation();
await conversation.addConversationToFirestore(booking.posting.host); //additional method working fine
String text = "Hi, my name is ${AppConstants.currentUser.firstName}";
await conversation.addMessageToFirestore(text); //additional method working fine
//this is where i should navigate to the conversation page and facing the error here
Navigator.push(
context, //error here context undefined
MaterialPageRoute(builder:
(context) => ConversationPage(conversation: conversation,),
),
);
}
class ConversationPage extends StatefulWidget {
final Conversation conversation;
static final String routeName = '/conversationPageRoute';
ConversationPage({this.conversation, Key key}) : super(key: key);
#override
_ConversationPageState createState() => _ConversationPageState();
}
class _ConversationPageState extends State<ConversationPage> {
Conversation _conversation;
// additional code of wiget build
}
I don't know where your function resides, so this is some general advice:
If you cannot access a variable in your method you have two options: pass it in as a parameter from the caller. Or return the result to the caller so they can do the part where the variable is needed themselves.
What does that mean for your scenario: either you need the context as an additional parameter in your method, or you need to return Future<Conversation> from your method and handle the navigation where it's called.
Personally, I'd favor the second option, since your business logic of starting a conversation and your in-app navigation are two different concerns that should not be mixed in one method.
If you want to call the navigator method anywhere in the app.
class NavigationService {
final GlobalKey<NavigatorState> globalKey = GlobalKey<NavigatorState>();
Future<dynamic> navigateTo(Route Route) {
return globalKey.currentState.push(Route);
}
}
and in main.dart.
navigatorKey: NavigationService().globalKey,
and then anywhere within the app.
Just use this
Future<void> addBookingConversation(Booking booking) async {
Conversation conversation = Conversation();
await conversation.addConversationToFirestore(booking.posting.host);
//additional method working fine
String text = "Hi, my name is ${AppConstants.currentUser.firstName}";
await conversation.addMessageToFirestore(text); //additional method working
fine
//this is where i should navigate to the conversation page and facing the
error here
NavigationService().navigateTo(
MaterialPageRoute(builder:
(context) => ConversationPage(conversation: conversation,),
),);
}
Wrap your Navigator inside :
WidgetsBinding.instance.addPostFrameCallback((_){
// 👈 Your Navigation here
});
Your Code:
Future<void> addBookingConversation(Booking booking) async {
...
WidgetsBinding.instance.addPostFrameCallback((_){
Navigator.push( //👈 add your navigation here
context, //error here context undefined
MaterialPageRoute(builder:
(context) => ConversationPage(conversation: conversation,),
),
);
...
}
This method help you to navigate the route without FutureBuilder. see the code
onPressed: () async {
// then await the future You want to complete and then use `.then()`
//method to implement the code that you want to implement when the future is completed
await //call your future widget //
.then((result) {
print('future completed');
// Navigate here
// For errors use onError to show or check the errors.
}).onError((error, stackTrace) {
print(error);
});
}
Below is the code of a provider class. Whenever the app starts i want to get the forms which were saved in the shared preferences. However it is taking sometime to load the from sharedpreferences. So When i access the forms for the first time it is initially empty, im getting an empty list. Is there anyway to delay the getter until it has the objects of form model.
class FormProvider with ChangeNotifier {
FormProvider() {
loadformPreferences();
}
List<FormModel> _forms = [];
List<FormModel> get forms => _forms;
Future<void> saveForm(FormModel form) async {
_forms.add(form);
await saveformPreferences();
notifyListeners();
}
Future<void> saveformPreferences() async {
List<String> myforms = _forms.map((f) => json.encode(f.toJson())).toList();
SharedPreferences prefs = await SharedPreferences.getInstance();
await prefs.setStringList('forms', myforms);
}
Future<void> loadformPreferences() async {
// WidgetsFlutterBinding.ensureInitialized();
SharedPreferences prefs = await SharedPreferences.getInstance();
var result = prefs.getStringList('forms');
if (result != null) {
_forms = result.map((f) => FormModel.fromJson(json.decode(f))).toList();
}
}
}
In Flutter, all actions related to building the UI must not be asynchronous (or expensive) in order to main a high frame-rate.
Thus, even if you could hypothetically find a way to "wait" for the results from SharedPreferences, this would not be desirable, since whatever waiting was done would block the UI from making progress.
Thus, there are a couple approaches to this common problem:
Handle initial state explicitly in the UI
The simplest solution is to explicitly handle the case where the Provider has not yet fetched its data, by representing some sort of initial state in your Provider. One easy way to do this is to initialize _forms to null instead of []. Then in your Widget.build method, you could do something specific (like show a loading spinner) when the result is null:
Widget build(BuildContext context) {
final provider = Provider.of<FormProvider>(context);
if (provider.forms == null) {
return CircularProgressIndicator();
}
// Otherwise, Do something useful with provider.forms
}
Construct your provider with the resolved data
Let's say that you don't use the FormProvider until the user performs an action, like click a button, at which point you push a new view onto the navigator with the FormProvider.
If you wish to guarantee that the FormProvider will always be initialized with the SharedPreferences values, then you can delay the construction of the new view until SharedPreferences has finished:
class MyButton extends StatelessWidget {
Widget build(BuildContext context) {
return Button(onClick: () async {
final forms = await _fetchFormsFromSharedPrefs();
Navigator.push(context, MaterialPageView(builder: (context) =>
Provider(create: (_) => FormProvider(forms))));
});
}
}