Call provider function in initstate

[mhd-barikhan]

there is an issue when try to call provider function inside initState() method

I'm using it as the following:

@OverRide

initState()
{
  super.initState();

  Provider.of<DataProvider>(context, listen: false).getData();

} 

the error log is:

I/flutter (15687):   * Ensure the Provider<DataProvider> is an ancestor to this MyHomePage Widget
I/flutter (15687):   * Provide types to Provider<DataProvider>
I/flutter (15687):   * Provide types to Consumer<DataProvider>
I/flutter (15687):   * Provide types to Provider.of<DataProvider>()
I/flutter (15687):   * Always use package imports. Ex: `import 'package:my_app/my_code.dart';
I/flutter (15687):   * Ensure the correct `context` is being used.
I/flutter (15687):
I/flutter (15687): If none of these solutions work, please file a bug at:
I/flutter (15687): https://github.com/rrousselGit/provider/issues

can you look into the issue, i've added listen: false but still show error.

Thanks

[rrousselGit]

Have you tried doing what the error suggests?
This is an error on your end. You likely forgot to add a provider, or inserted it in the wrong place.

[mhd-barikhan]

this is my full code:

main.dart

import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import 'package:provider_data_app/Provider/DataProvider.dart';
import 'package:provider_data_app/mainUI.dart';




void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return  MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
      
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(),
    );

    
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key}) : super(key: key);


  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {


@override
initState()
{
  super.initState();
 Provider.of<DataProvider>(context, listen: false).getData();


} 



  @override
  Widget build(BuildContext context) {

    return  ChangeNotifierProvider(
          
          builder: (_) => DataProvider(),
          
          child: MainUI()
          );
            
      


    
  }










}

MainUI.dart

import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import 'package:provider_data_app/Provider/DataProvider.dart';


class MainUI extends StatelessWidget {



  @override
  Widget build(BuildContext context) {



return Scaffold(
      appBar: AppBar(
      
        title: Text('provider app'),
      ),
      body: Center(

        child:  Consumer<DataProvider>(
  builder: (context, dataProvider, child) {

      return dataProvider.isBusy? Text('busy') :  Text(dataProvider.dbVersion);

  }
        )
    
       
      ),
      floatingActionButton: FloatingActionButton(
        //listen false to rebuild only inside Consumer not full widget
       onPressed:()=> Provider.of<DataProvider>(context,listen: false).getData(),
        tooltip: 'Increment',
        child: Icon(Icons.add),
      
  
      )

  
       
    );

  }
}

DataProvider.dart

import 'package:flutter/foundation.dart';
import 'package:http/http.dart' as http;
import 'dart:convert';



class DataProvider with ChangeNotifier {
  String _dbVersion = '';
  String get dbVersion => _dbVersion;

  bool _isBusy=false;
  bool get isBusy => _isBusy;



  set isBusy(bool value)
  {
      _isBusy=value;
      notifyListeners();
  }

  Future<void> getData() async{
  


          isBusy=true;
      
          _dbVersion=await getDbVersion();

         

          isBusy=false;
        
        
          

    

}




  Future<String> getDbVersion() async {
   return '2.2.0';
   }






}

i don't know why Provider.of(context, listen: false).getData(); not working in initstate and give me an error

[adriancmurray]

@rrousselGit gave the answer, you're inserting it in the wrong place. Your initState is calling a function on a Provider that hasn't been built yet. You need to create the provider and then call that function later down the widget tree in a different initstate.

[renanserrou]

Try to setup your ChangeNotifierProvider before MaterialApp.

[karmazinkd]

For anyone who is reading this thread and still doesn't know what to do here is a great explanation: https://pub.dev/packages/provider#faq and the first question:

I have an exception when obtaining Providers inside initState. What can I do?

[Santiago1709]

I'd say it is because you are calling a setState() when notifying listeners, and you cant do that when widgets are building. You should this:

void initState() {
WidgetsBinding.instance.addPostFrameCallback((_) {
Provider.of(context,listen:false).yourFunctionWithNotifyListener();
});
super.initState();
}

!!REMEMBER TO ADD LISTEN:FALSE

[sanba-anass]

context is not avaliable in initstate how we can call it in initstate anyway

[bhanuka96]

@rrousselGit

It is safe to use provider in initState without using addPostFrameCallback if there are no rebuilding things like (notifyListeners or showing alert). right?

Example:

@override
void initState() {
super.initState();
var userNotifier = Provider.of<ValueNotifier<UserModel>>(context, listen: false); <-- already has value
controller.text = userNotifier.value.displayName;
 }

[sajibsaha4647]

@bhanuka96 getting error ...`import 'package:flutter/material.dart';
import 'package:fluttermvvm/Utils/Routes/Routes.dart';
import 'package:fluttermvvm/Utils/Routes/RoutesName.dart';
import 'package:fluttermvvm/View/LoginScreen.dart';
import 'package:fluttermvvm/ViewModel/AuthViewmodel/AuthViewModel.dart';
import 'package:fluttermvvm/ViewModel/AuthViewmodel/RegistrationViewModel.dart';
import 'package:provider/provider.dart';

import 'ViewModel/HomeViewModel/HomeViewModel.dart';
import 'ViewModel/UserViewModel/UserViewModel.dart';

void main() {
runApp(const MyApp());
}

class MyApp extends StatelessWidget {
const MyApp({Key? key}) : super(key: key);

// This widget is the root of your application.
@OverRide
Widget build(BuildContext context) {
return MultiProvider(providers: [
ChangeNotifierProvider(create: ()=>AuthViewmodel()),
ChangeNotifierProvider(create: ()=>RegistrationViewModel()),
ChangeNotifierProvider(create: ()=>UserViewModel()),
ChangeNotifierProvider(create: ()=>HomeViewModel()),

],child: MaterialApp(
  debugShowCheckedModeBanner: false,
  initialRoute: RoutesName.splashscreen,
  onGenerateRoute: Routes.generateRoute ,
  theme: ThemeData(
    primarySwatch: Colors.blue,
  ),
  home: LoginScreen(),
));

}
}

`

[sajibsaha4647]

` @OverRide

void initState() {
super.initState();
var UserDatamodels = Provider.of(context) ;
UserDatamodels.fetchUserDataApi();
}`

[sajibsaha4647]

after using app going crash please help ??

[bhanuka96]

@sajibsaha4647 Use this way

var UserDatamodels = Provider.of(context, listen: false) ;
UserDatamodels.fetchUserDataApi(); // don't use any setState(notifyListeners) inside this model.

use this way If you want to use setState or notifyListerners after calling you function

WidgetsBinding.instance.addPostFrameCallback((_) {
var UserDatamodels = Provider.of(context, listen: false) ;
UserDatamodels.fetchUserDataApi();
});

[AdnanGriezmann]

how i use stateless widget with provider statemanagement

[AdnanGriezmann]

i call api but i want to not using statefullwidget or inistate method how can i achieve provider api call without initstate method.
help plz