FirebaseCloudMessaging：PlatformException（PlatformException（null-error，主机平台返回非空返回值的空值。，null，null））

Question

我正在尝试从 Node.js API 向 Flutter 应用程序发送通知。\n首先，我想让我的应用程序能够接收来自 Firebase 的通知。

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但是，当我初始化App时，我遇到了一个问题：

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PlatformException (PlatformException(null-error, 主机平台\n非空返回值返回空值。, null, null))

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在控制台中：

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E/flutter (25357): [ERROR:flutter/lib/ui/ui_dart_state.cc(198)] Unhandled Exception: PlatformException(null-error, Host platform returned null value for non-null return value., null, null)\nE/flutter (25357): #0      FirebaseCoreHostApi.optionsFromResource (package:firebase_core_platform_interface/src/pigeon/messages.pigeon.dart:250)\npackage:firebase_core_platform_interface/\xe2\x80\xa6/pigeon/messages.pigeon.dart:1\nE/flutter (25357): <asynchronous suspension>\nE/flutter (25357): #1      MethodChannelFirebase.initializeApp (package:firebase_core_platform_interface/src/method_channel/method_channel_firebase.dart:89)\npackage:firebase_core_platform_interface/\xe2\x80\xa6/method_channel/method_channel_firebase.dart:1\nE/flutter (25357): <asynchronous suspension>\nE/flutter (25357): #2      Firebase.initializeApp (package:firebase_core/src/firebase.dart:40)\npackage:firebase_core/src/firebase.dart:1\nE/flutter (25357): <asynchronous suspension>\nE/flutter (25357): #3      main (package:notifappfcm/main.dart:13)\npackage:notifappfcm/main.dart:1\n

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我一直在寻找解决这个问题的办法，但实在找不到。

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这是我的应用程序代码：

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主程序.dart

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import \'package:firebase_messaging/firebase_messaging.dart\';\nimport \'package:flutter/material.dart\';\nimport \'package:firebase_core/firebase_core.dart\';\nimport \'mainscreen.dart\';\n\nFuture<void> _firebadeMessagingBackgroundHandler(RemoteMessage message) async {\n  await Firebase.initializeApp(); // options: DefaultFirebaseConfig.platformOptions\n  print(\'Handling a background message ${message.messageId}\');\n}\n\nvoid main() async {\n  WidgetsFlutterBinding.ensureInitialized();\n  await Firebase.initializeApp();\n\n  FirebaseMessaging.onBackgroundMessage(_firebadeMessagingBackgroundHandler);\n\n  runApp(const MyApp());\n}\n\nclass MyApp extends StatelessWidget {\n  const MyApp({Key? key}) : super(key: key);\n\n  @override\n  Widget build(BuildContext context) {\n    return MaterialApp(\n      title: \'Flutter Demo\',\n      theme: ThemeData(\n        primarySwatch: Colors.blue,\n      ),\n      home: const MainScreen(),\n    );\n  }\n}\n\nclass MyHomePage extends StatefulWidget {\n  const MyHomePage({Key? key, required this.title}) : super(key: key);\n\n  final String title;\n\n  @override\n  State<MyHomePage> createState() => _MyHomePageState();\n}\n\nclass _MyHomePageState extends State<MyHomePage> {\n  int _counter = 0;\n\n \n  void _incrementCounter() {\n    setState(() {\n      _counter++;\n    });\n  }\n\n @override\n  void initState() {\n    super.initState();\n  }\n\n  \n  @override\n  Widget build(BuildContext context) {\n    return Scaffold(\n      appBar: AppBar(\n        title: Text(widget.title),\n      ),\n      body: Center(\n        child: Column(\n          mainAxisAlignment: MainAxisAlignment.center,\n          children: <Widget>[\n            const Text(\n              \'You have pushed the button this many times:\',\n            ),\n            Text(\n              \'$_counter\',\n              style: Theme.of(context).textTheme.headline4,\n            ),\n          ],\n        ),\n      ),\n      floatingActionButton: FloatingActionButton(\n        onPressed: _incrementCounter,\n        tooltip: \'Increment\',\n        child: const Icon(Icons.add),\n      ),\n    );\n  }\n}\n

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主屏幕.dart

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import \'package:firebase_messaging/firebase_messaging.dart\';\nimport \'package:flutter/foundation.dart\';\nimport \'package:flutter/material.dart\';\nimport \'package:flutter_local_notifications/flutter_local_notifications.dart\';\n\nclass MainScreen extends StatefulWidget {\n  const MainScreen({Key? key}) : super(key: key);\n\n  @override\n  State<MainScreen> createState() => _MainScreenState();\n}\n\nclass _MainScreenState extends State<MainScreen> {\n  late AndroidNotificationChannel channel;\n  late FlutterLocalNotificationsPlugin flutterLocalNotificationsPlugin;\n\n  @override\n  void initState() {\n    super.initState();\n\n    requestPermission();\n    loadFCM();\n    listenFCM();\n    // Get device\'s notification token\n    getToken();\n  }\n\n\n  void getToken() async {\n    await FirebaseMessaging.instance.getToken().then((token) => print(token));\n  }\n\n  void requestPermission() async {\n    FirebaseMessaging messaging = FirebaseMessaging.instance;\n\n    NotificationSettings settings = await messaging.requestPermission(\n      alert: true,\n      announcement: false,\n      badge: true,\n      carPlay: false,\n      criticalAlert: false,\n      provisional: false,\n      sound: true,\n    );\n\n    if (settings.authorizationStatus == AuthorizationStatus.authorized) {\n      print(\'User granted permission\');\n    } else if (settings.authorizationStatus ==\n        AuthorizationStatus.provisional) {\n      print(\'User granted provisional permission\');\n    } else {\n      print(\'User declined or has not accepted permission\');\n    }\n  }\n\n  void listenFCM() async {\n    FirebaseMessaging.onMessage.listen((RemoteMessage message) {\n      RemoteNotification? notification = message.notification;\n      AndroidNotification? android = message.notification?.android;\n      if (notification != null && android != null && !kIsWeb) {\n        flutterLocalNotificationsPlugin.show(\n            notification.hashCode,\n            notification.title,\n            notification.body,\n            NotificationDetails(\n                android: AndroidNotificationDetails(channel.id, channel.name,\n                    // ignore: todo\n                    // TODO add a proper drawable resource to android (now using one that already exists)\n                    icon: \'launch_background\')));\n      }\n    });\n  }\n\n  void loadFCM() async {\n    if (!kIsWeb) {\n      channel = const AndroidNotificationChannel(\n        \'high_importance_channel\', // id\n        \'High Importance Notifications\', // title\n        importance: Importance.high,\n        enableVibration: true,\n      );\n\n      flutterLocalNotificationsPlugin = FlutterLocalNotificationsPlugin();\n\n      /// Create an Android Notification Channel.\n      ///\n      /// We use this channel in the `AndroidManifest.xml` file to override the\n      /// default FCM channel to enable heads up notifications.\n      await flutterLocalNotificationsPlugin\n          .resolvePlatformSpecificImplementation<\n              AndroidFlutterLocalNotificationsPlugin>()\n          ?.createNotificationChannel(channel);\n\n      /// Update the iOS foreground notification presentation options to allow\n      /// heads up notifications.\n      await FirebaseMessaging.instance\n          .setForegroundNotificationPresentationOptions(\n        alert: true,\n        badge: true,\n        sound: true,\n      );\n    }\n  }\n\n  @override\n  Widget build(BuildContext context) {\n    return Scaffold(\n        body: Center(\n      child: Container(\n        height: 40,\n        width: 200,\n        color: Colors.red,\n      ),\n    ));\n  }\n}\n

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Answer 1

确保您已在项目级build.gradle文件和应用程序级build.gradle文件中添加 Firebase SDK 依赖项

要在项目级别build.gradle中添加的依赖项：

buildscript {
  repositories {
    // Check that you have the following line (if not, add it):
    google()  // Google's Maven repository
  }
  dependencies {
    ...
    // Add this line
    classpath 'com.google.gms:google-services:4.3.13'
  }
}

allprojects {
  ...
  repositories {
    // Check that you have the following line (if not, add it):
    google()  // Google's Maven repository
    ...
  }
}

要在应用程序级别build.gradle中添加的依赖项：

apply plugin: 'com.android.application'
// Add this line
apply plugin: 'com.google.gms.google-services'

dependencies {
  // Import the Firebase BoM
  implementation platform('com.google.firebase:firebase-bom:30.2.0')

  // Add the dependency for the Firebase SDK for Google Analytics
  // When using the BoM, don't specify versions in Firebase dependencies
  implementation 'com.google.firebase:firebase-analytics'

  // Add the dependencies for any other desired Firebase products
  // https://firebase.google.com/docs/android/setup#available-libraries
}

Answer 2

注意力。如上所述手动更改 build.gradle 文件不是解决方案。它要么不起作用，要么每次构建都会在使用已弃用的依赖项时生成大量警告。正确的解决方案是这样的：Firebase 应该像下面这样初始化：

await Firebase.initializeApp(
  options: DefaultFirebaseOptions.currentPlatform,
);

为此，您需要从命令行/终端运行一些命令：

// Add firebase core into your project
flutter pub add firebase_core
// Generate firebase options file
flutterfire configure

然后您需要将这些导入您的 .dart 文件中：

// Import firebase core and generated file
import 'package:firebase_core/firebase_core.dart';
import 'firebase_options.dart';

详细信息您可以参考这里。

Answer 3

确保您的计算机中有这些设置android/build.gradle

buildscript {

  repositories {
    // Check that you have the following line (if not, add it):
    google()  // Google's Maven repository
  }

  dependencies {
    // ...

    // Add the following line:
    classpath 'com.google.gms:google-services:4.3.13'  // Google Services plugin
  }
}

allprojects {
  // ...

  repositories {
    // Check that you have the following line (if not, add it):
    google()  // Google's Maven repository
    // ...
  }
}

然后在你的android/app/build.gradle：

apply plugin: 'com.android.application'
// Add the following line:
apply plugin: 'com.google.gms.google-services'  // Google Services plugin

android {
  // ...
}

您可以按照此处的步骤操作

并且不要忘记从 firebase 项目控制台下载 google-service.json ，并将其放入 android/app 文件夹中。

Answer 4

从：

await Firebase.initializeApp();

到：

await Firebase.initializeApp(options: DefaultFirebaseOptions.currentPlatform);

对我有用！

Answer 5

有时 FlutterFire cli 无法更新 build.gradle 文件，因此您会收到上述错误

在项目级别 build.gradle 添加 firebase 依赖项

   dependencies {
    classpath 'com.android.tools.build:gradle:7.1.2'
    classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
    classpath 'com.google.gms:google-services:4.3.10'
    classpath 'com.google.firebase:firebase-crashlytics-gradle:2.8.1'
}

在应用程序级别 build.gradle 文件中应用 firebase 插件

    apply plugin: 'com.google.gms.google-services'
    apply plugin: 'com.google.firebase.crashlytics'

Answer 6

我已将类路径从类路径更改com.google.gms:google-services:4.4.0为类路径com.google.gms:google-services:4.3.15并为我工作。