I'm learning Flutter by following the relatively recent tutorial (made in February - LINK) and while I wrote the same code as author I'm getting the following exception:

======== Exception caught by widgets library =======================================================
The following FirebaseException was thrown building FutureBuilder<FirebaseApp>(dirty, state: _FutureBuilderState<FirebaseApp>#881ee):
[core/no-app] No Firebase App '[DEFAULT]' has been created - call Firebase.initializeApp()

The relevant error-causing widget was: 
  FutureBuilder<FirebaseApp> FutureBuilder:file:///C:/Users/Mrky/Desktop/Sve/Faks/10_semestar/mynotes/lib/main.dart:30:13
When the exception was thrown, this was the stack: 
#0      MethodChannelFirebase.app (package:firebase_core_platform_interface/src/method_channel/method_channel_firebase.dart:173:5)
#1      Firebase.app (package:firebase_core/src/firebase.dart:53:41)
#2      FirebaseAuth.instance (package:firebase_auth/src/firebase_auth.dart:38:47)
#3      HomePage.build.<anonymous closure> (package:mynotes/main.dart:37:34)
#4      _FutureBuilderState.build (package:flutter/src/widgets/async.dart:615:55)
#5      StatefulElement.build (package:flutter/src/widgets/framework.dart:4919:27)
#6      ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4806:15)
#7      StatefulElement.performRebuild (package:flutter/src/widgets/framework.dart:4977:11)
#8      Element.rebuild (package:flutter/src/widgets/framework.dart:4529:5)
#9      BuildOwner.buildScope (package:flutter/src/widgets/framework.dart:2659:19)
#10     WidgetsBinding.drawFrame (package:flutter/src/widgets/binding.dart:891:21)
#11     RendererBinding._handlePersistentFrameCallback (package:flutter/src/rendering/binding.dart:370:5)
#12     SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:1146:15)
#13     SchedulerBinding.handleDrawFrame (package:flutter/src/scheduler/binding.dart:1083:9)
#14     SchedulerBinding._handleDrawFrame (package:flutter/src/scheduler/binding.dart:997:5)
#18     _invoke (dart:ui/hooks.dart:151:10)
#19     PlatformDispatcher._drawFrame (dart:ui/platform_dispatcher.dart:308:5)
#20     _drawFrame (dart:ui/hooks.dart:115:31)
(elided 3 frames from dart:async)
==========================================================================================

The code that I have currently written is:

import 'package:firebase_core/firebase_core.dart';
import 'package:flutter/material.dart';
import 'package:firebase_auth/firebase_auth.dart';
import 'package:mynotes/firebase_options.dart';
import 'package:mynotes/views/login_view.dart';


void main() {
  WidgetsFlutterBinding.ensureInitialized();
  runApp(
    MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.green,
      ),
      home: const HomePage(),
    ),
  );
}

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

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('Home'),
      ),
      body: FutureBuilder(
        future: Firebase.initializeApp(
          options: DefaultFirebaseOptions.currentPlatform,
        ),
        builder: (context, snapshot) {
          switch (snapshot.connectionState) {
            case ConnectionState.done:
              print(FirebaseAuth.instance.currentUser);
              return const Text('Done');
            default:
              return const Text('Loading...');
          }
        },
      ),
    );
  }
}

As it is visible I have Firebase.initializeApp inside future of FutureBuilder. Also If I comment out the line print(FirebaseAuth.instance.currentUser); the app will show text Done without any problem.

CodePudding user response：

Run flutter clean, then add the dart pub package firebase_core with the command flutter pub add firebase_core. Finally, run flutter pub get to resolve all the dependencies.

CodePudding user response：

Make your void function async and add the following lines inside your void main.

void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  await Firebase.initializeApp();

  runApp(const MyApp());
}