Flutter后台消息处理插件flutter_background_messenger的使用

当然，以下是一个关于如何在Flutter中使用flutter_background_messenger插件来处理后台消息的示例代码。flutter_background_messenger插件允许应用在后台接收和处理消息，这在实现推送通知等功能时非常有用。

首先，确保你已经在pubspec.yaml文件中添加了flutter_background_messenger依赖：

dependencies:
  flutter:
    sdk: flutter
  flutter_background_messenger: ^x.y.z  # 替换为最新版本号

然后，运行flutter pub get来安装依赖。

接下来，你需要配置Android和iOS项目以支持后台消息处理。这里主要展示如何在Android上进行配置（iOS的配置过程类似，但涉及不同的文件和方法）。

Android配置

在android/app/src/main/AndroidManifest.xml中添加必要的权限和服务声明：

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.yourapp">

    <uses-permission android:name="android.permission.INTERNET"/>
    <uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED"/>
    <uses-permission android:name="com.google.android.c2dm.permission.RECEIVE" />

    <application
        ...>
        
        <!-- Firebase Messaging Service -->
        <service
            android:name=".MyFirebaseMessagingService"
            android:exported="true">
            <intent-filter>
                <action android:name="com.google.firebase.MESSAGING_EVENT" />
            </intent-filter>
        </service>
        
        <!-- Background Messenger Service -->
        <service
            android:name="com.dexterous.flutterlocalnotifications.FlutterLocalNotificationService"
            android:exported="false"/>
        <receiver android:name="com.dexterous.flutterlocalnotifications.ScheduledNotificationBootReceiver">
            <intent-filter>
                <action android:name="android.intent.action.BOOT_COMPLETED"/>
            </intent-filter>
        </receiver>
        
    </application>
</manifest>

创建Firebase Messaging Service

在android/app/src/main/kotlin/com/example/yourapp/（或对应的Java目录）下创建一个名为MyFirebaseMessagingService.kt的文件（如果是Java，则扩展名为.java）：

package com.example.yourapp

import android.util.Log
import com.google.firebase.messaging.FirebaseMessagingService
import com.google.firebase.messaging.RemoteMessage
import io.flutter.embedding.engine.FlutterEngineCache
import io.flutter.embedding.engine.dart.DartExecutor
import io.flutter.plugins.firebasemessaging.FlutterFirebaseMessagingService

class MyFirebaseMessagingService : FlutterFirebaseMessagingService() {

    override fun onMessageReceived(remoteMessage: RemoteMessage) {
        // 处理接收到的消息
        Log.d("FirebaseMessaging", "From: ${remoteMessage.from}")

        // 调用Flutter后台消息处理
        handleBackgroundMessage(remoteMessage.data)
    }

    private fun handleBackgroundMessage(data: Map<String, String>) {
        FlutterEngineCache
            .getInstance()
            .get("my_engine_id")  // 确保在FlutterActivity或FlutterFragment中设置了相同的engine ID
            ?.dartExecutor
            ?.executeDartEntrypoint(
                DartExecutor.DartEntrypoint.createDefault()
            ) { result ->
                // 发送消息到Flutter
                val channel = FlutterEngineCache.getInstance().get("my_engine_id")?.dartExecutor?.binaryMessenger
                                ?.getMessagingChannel()
                channel?.invokeMethod("backgroundMessageHandler", data)
            }
    }
}

Flutter代码

在你的Flutter项目中，初始化flutter_background_messenger并设置后台消息处理器：

import 'package:flutter/material.dart';
import 'package:flutter_local_notifications/flutter_local_notifications.dart';
import 'package:flutter_background_messenger/flutter_background_messenger.dart';
import 'package:firebase_messaging/firebase_messaging.dart';

void main() {
  WidgetsFlutterBinding.ensureInitialized();
  FlutterBackgroundMessenger.initialize(
    onBackgroundMessage: myBackgroundMessageHandler,
  );
  runApp(MyApp());
}

Future<void> myBackgroundMessageHandler(Map<String, dynamic> message) async {
  // 处理后台消息
  print("Background message: $message");

  // 显示本地通知（可选）
  final FlutterLocalNotificationsPlugin flutterLocalNotificationsPlugin = FlutterLocalNotificationsPlugin();
  var androidPlatformChannelSpecifics = AndroidNotificationDetails(
    'your_channel_id',
    'Your Channel Name',
    'Your Channel Description',
    importance: Importance.max,
    priority: Priority.high,
  );
  var iOSPlatformChannelSpecifics = IOSNotificationDetails();
  var platformChannelSpecifics = NotificationDetails(
    androidPlatformChannelSpecifics,
    iOSPlatformChannelSpecifics,
  );
  await flutterLocalNotificationsPlugin.show(
    0,
    'Background Message',
    'You have a new background message: ${message['body'] ?? 'No message body'}',
    platformChannelSpecifics,
    payload: 'item x',
  );
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: Text('Flutter Background Messenger Demo'),
        ),
        body: Center(
          child: Text('Check your console for background messages.'),
        ),
      ),
    );
  }
}

注意事项

1. Engine ID：确保在FlutterActivity或FlutterFragment中设置了与FlutterEngineCache.getInstance().get("my_engine_id")相同的engine ID。
2. 通知权限：在应用启动时请求通知权限，并确保用户已授予权限。
3. Firebase配置：确保你的Firebase项目已正确配置，包括在google-services.json中包含了所有必要的配置信息。

这个示例展示了如何在Flutter中使用flutter_background_messenger插件来处理后台消息，并通过本地通知向用户显示消息内容。根据你的具体需求，你可能需要调整消息处理逻辑和通知显示方式。