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この dart ファイルで、「ビルド中に setState() または markNeedsBuild() が呼び出されました」というエラーが表示されます。ここでは、Futurebuilder を呼び出して getUser() 認証情報を取得しています。基本的には、ユーザーがログインしているかどうかを確認してから、それぞれの画面に移動しています。

参考までにコードを貼り付けておきます。ありがとう。

import 'package:flutter/material.dart';
import 'package:mukti/ui_pages/login_signup/login_screen.dart';
import 'package:firebase_auth/firebase_auth.dart' as auth;
import 'package:mukti/ui_pages/main_screen/main_screen.dart';
import 'package:provider/provider.dart';

import 'authService.dart';

class CheckAuthentication extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      home: FutureBuilder(
        future: Provider.of<AuthService>(context, listen: false).getUser(),
        builder: (context, AsyncSnapshot<auth.User> snapshot) {
          if (snapshot.connectionState == ConnectionState.done) {
            if (snapshot.error != null) {
              print("error");
              return Text(snapshot.error.toString());
            }
            return snapshot.hasData ? MainScreen(firebaseUser: snapshot.data) : LoginScreen();
          } else {
            return LoadingCircle();
          }
        }
      )
    );
  }
}

class LoadingCircle extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Center(
      child: Container(
        child: CircularProgressIndicator(
          backgroundColor: Theme.of(context).colorScheme.primaryVariant,
        ),
        alignment: Alignment(0.0, 0.0),
      ),
    );
  }
}

参照用の例外メッセージ

════════ Exception caught by foundation library ════════════════════════════════════════════════════
The following assertion was thrown while dispatching notifications for AuthService:
setState() or markNeedsBuild() called during build.

This _InheritedProviderScope<AuthService> widget cannot be marked as needing to build because the framework is already in the process of building widgets.  A widget can be marked as needing to be built during the build phase only if one of its ancestors is currently building. This exception is allowed because the framework builds parent widgets before children, which means a dirty descendant will always be built. Otherwise, the framework might not visit this widget during this build phase.
The widget on which setState() or markNeedsBuild() was called was: _InheritedProviderScope<AuthService>
  value: Instance of 'AuthService'
  listening to value
The widget which was currently being built when the offending call was made was: CheckAuthentication
  dirty
When the exception was thrown, this was the stack: 
#0      Element.markNeedsBuild.<anonymous closure> (package:flutter/src/widgets/framework.dart:4292:11)
#1      Element.markNeedsBuild (package:flutter/src/widgets/framework.dart:4307:6)
#2      _InheritedProviderScopeElement.markNeedsNotifyDependents (package:provider/src/inherited_provider.dart:496:5)
#3      ChangeNotifier.notifyListeners (package:flutter/src/foundation/change_notifier.dart:226:25)
#4      AuthService.getUser (package:mukti/authentication/authService.dart:18:7)
...
The AuthService sending notification was: Instance of 'AuthService'
════════════════════════════════════════════════════════════════════════════════════════════════════
4

3 に答える 3

0

参照用の getUser()

final auth.FirebaseAuth _auth = auth.FirebaseAuth.instance;

  Future<auth.User> getUser() async {
    try {
      final user = _auth.currentUser;
      if (user != null) {
        print('User signed in: ${user.email}');
      } else {
        print('No user signed in');
      }
      notifyListeners();
      return user;
    } catch (e) {
      print(e);
      return null;
    }
  }
于 2021-01-07T02:00:50.873 に答える