针对 Flutter 错误“插件未添加”放大验证插件

问题描述 投票：0回答：2

我正在使用 Amplify 和 Flutter 进行用户身份验证，但无法检索用户的会话。我得到的错误：

> Launching lib/main.dart on 2109119DG in debug mode...
Running Gradle task 'assembleDebug'...
✓  Built build/app/outputs/flutter-apk/app-debug.apk.
Debug service listening on ws://xxxx
Syncing files to device 2109119DG...
I/amplify:flutter:auth_cognito(27806): Added Auth plugin
E/flutter (27806): [ERROR:flutter/runtime/dart_vm_initializer.cc(41)] Unhandled Exception: AmplifyException(message: Auth plugin has not been added to Amplify, recoverySuggestion: Add Auth plugin to Amplify and call configure before calling Auth related APIs, underlyingException: null)
E/flutter (27806): #0      AuthCategory.fetchAuthSession (package:amplify_core/src/category/amplify_auth_category.dart:189:11)
E/flutter (27806): #1      _MyAppState.isUserSignedIn (package:base_app/main.dart:37:39)
E/flutter (27806): #2      _MyAppState.build (package:base_app/main.dart:47:21)
E/flutter (27806): #3      StatefulElement.build (package:flutter/src/widgets/framework.dart:4992:27)
E/flutter (27806): #4      ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4878:15)
E/flutter (27806): #5      StatefulElement.performRebuild (package:flutter/src/widgets/framework.dart:5050:11)
E/flutter (27806): #6      Element.rebuild (package:flutter/src/widgets/framework.dart:4604:5)
E/flutter (27806): #7      ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:4859:5)
E/flutter (27806): #8      StatefulElement._firstBuild (package:flutter/src/widgets/framework.dart:5041:11)
E/flutter (27806): #9      ComponentElement.mount (package:flutter/src/widgets/framework.dart:4853:5)
E/flutter (27806): #10     Element.inflateWidget (package:flutter/src/widgets/framework.dart:3863:16)
E/flutter (27806): #11     Element.updateChild (package:flutter/src/widgets/framework.dart:3592:18)
E/flutter (27806): #12     RenderObjectToWidgetElement._rebuild (package:flutter/src/widgets/binding.dart:1195:16)
E/flutter (27806): #13     RenderObjectToWidgetElement.mount (package:flutter/src/widgets/binding.dart:1164:5)
E/flutter (27806): #14     RenderObjectToWidgetAdapter.attachToRenderTree.<anonymous closure> (package:flutter/src/widgets/binding.dart:1111:18)
E/flutter (27806): #15     BuildOwner.buildScope (package:flutter/src/widgets/framework.dart:2605:19)
E/flutter (27806): #16     RenderObjectToWidgetAdapter.attachToRenderTree (package:flutter/src/widgets/binding.dart:1110:13)
E/flutter (27806): #17     WidgetsBinding.attachRootWidget (package:flutter/src/widgets/binding.dart:945:7)
E/flutter (27806): #18     WidgetsBinding.scheduleAttachRootWidget.<anonymous closure> (package:flutter/src/widgets/binding.dart:925:7)
E/flutter (27806): #19     Timer._createTimer.<anonymous closure> (dart:async-patch/timer_patch.dart:18:15)
E/flutter (27806): #20     _Timer._runTimers (dart:isolate-patch/timer_impl.dart:398:19)
E/flutter (27806): #21     _Timer._handleMessage (dart:isolate-patch/timer_impl.dart:429:5)
E/flutter (27806): #22     _RawReceivePortImpl._handleMessage (dart:isolate-patch/isolate_patch.dart:192:12)
E/flutter (27806): 
D/AWSMobileClient(27806): Using the SignInProviderConfig from `awsconfiguration.json`.
D/AWSMobileClient(27806): Inspecting user state details
I/flutter (27806): Successfully configured
D/AWSMobileClient(27806): Inspecting user state details
I/TetheringManager(27806): registerTetheringEventCallback:com.dontknow.base_app
D/AWSMobileClient(27806): hasFederatedToken: false provider: cognito-idp.eu-central-1.amazonaws.com/eu-central-1_xxxx
D/AWSMobileClient(27806): hasFederatedToken: false provider: cognito-idp.eu-central-1.amazonaws.com/eu-central-1_xxxx
D/AWSMobileClient(27806): Inspecting user state details
D/AWSMobileClient(27806): hasFederatedToken: true provider: cognito-idp.eu-central-1.amazonaws.com/eu-central-1_xxxx
D/AWSMobileClient(27806): waitForSignIn: userState:SIGNED_IN
D/AWSMobileClient(27806): getCredentials: Validated user is signed-in

我严格遵循AWS教程并在代码中调用“configure”之前添加了插件。同样奇怪的是，在错误发生之前的行中，插件实际上已加载。

这是我的 main.dart：

  State<MyApp> createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  @override
  void initState() {
    super.initState();
    _configureAmplify();
  }

  void _configureAmplify() async {
    try {
      await Amplify.addPlugin(AmplifyAuthCognito());
      await Amplify.configure(amplifyconfig);
      print('Successfully configured');
    } on Exception catch (e) {
      print('Error configuring Amplify: $e');
    }
  }

  Future<bool> isUserSignedIn() async {
    final result = await Amplify.Auth.fetchAuthSession();
    return result.isSignedIn;
  }

  @override
  Widget build(BuildContext context) {
    return Authenticator(
      child: MaterialApp(
        builder: Authenticator.builder(),
        home: FutureBuilder(
            future: isUserSignedIn(),
            builder: (BuildContext ctx, AsyncSnapshot snapshot) {
              if (snapshot.data == null) {
                return const Center(
                  child: CircularProgressIndicator(),
                );
              } else {
                return Text("logged in");
              }
            }),
      ),
    );
  }
}
flutter authentication amazon-cognito aws-amplify
2个回答
2
投票

您尝试在 

initState()
中执行异步工作，但这不能保证在调用 
build()
之前完成。因此，当您在 
Amplify.Auth.fetchAuthSession()
函数中调用 
build()
时，初始化和配置尚未完成。

您应该尝试在 

_configureAmplify()
之前致电 
runApp()
。

要完成此操作，您还需要在 

WidgetsFlutterBinding.ensureInitialized()
之前调用 
_configureAmplify()
。

一般建议，此类工作不属于 UI 代码（页面或小部件）。相反，应该在应用程序的状态管理中完成。

1
投票

最后我在这里找到了适合我的技能水平的合适修复程序github-repo

我添加了一个状态变量 

_isAmplifyConfigured
，当 
_configureAmplify()
完成时设置为 true。然后，在构建器中，我使用简单的 if-else 检查是否配置了 amplify。完整代码如下：

import 'package:amplify_auth_cognito/amplify_auth_cognito.dart';
import 'package:amplify_authenticator/amplify_authenticator.dart';
import 'package:amplify_flutter/amplify_flutter.dart';
import 'package:flutter/material.dart';

import 'amplifyconfiguration.dart';

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

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

  @override
  State<MyApp> createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  bool _isAmplifyConfigured = false;

  @override
  void initState() {
    super.initState();
    _configureAmplify();
  }

  void _configureAmplify() async {
    try {
      await Amplify.addPlugin(AmplifyAuthCognito());
      await Amplify.configure(amplifyconfig);
      setState(() => _isAmplifyConfigured = true);
      print('Successfully configured');
    } on Exception catch (e) {
      print('Error configuring Amplify: $e');
    }
  }

  Future<bool> isUserSignedIn() async {
    final result = await Amplify.Auth.fetchAuthSession();
    return result.isSignedIn;
  }

  @override
  Widget build(BuildContext context) {
    return Authenticator(
      child: MaterialApp(
        builder: Authenticator.builder(),
        home: _isAmplifyConfigured? FutureBuilder(
            future: isUserSignedIn(),
            builder: (BuildContext ctx, AsyncSnapshot snapshot) {
              if (snapshot.data == null) {
                return const Center(
                  child: CircularProgressIndicator(),
                );
              } else {
                return Text("logged in");
              }
            }): Text("not logged in")
      ),
    );
  }
}
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