Flutter Android Release模式下后台通知不显示但_handler已触发

针对你遇到的Debug模式前后台通知正常、Release模式仅前台收到通知但后台handler触发的问题，可从以下几个方面排查：

1. 确认Android通知渠道配置（Android 8.0+必选） #

Release模式下如果未创建通知渠道，系统会拦截后台通知。需在App初始化时创建通知渠道：

import 'package:flutter_local_notifications/flutter_local_notifications.dart';

void _createNotificationChannel() {
  const AndroidNotificationChannel channel = AndroidNotificationChannel(
    'high_importance_channel', // 渠道ID
    'High Importance Notifications', // 渠道名称
    description: 'This channel is used for important notifications.', // 渠道描述
    importance: Importance.max,
  );

  final FlutterLocalNotificationsPlugin flutterLocalNotificationsPlugin = FlutterLocalNotificationsPlugin();
  flutterLocalNotificationsPlugin.resolvePlatformSpecificImplementation<AndroidFlutterLocalNotificationsPlugin>()?.createNotificationChannel(channel);
}

在main函数中调用该方法，确保初始化时执行。

2. 检查Firebase消息类型 #

Firebase推送分为两种类型：

• 通知消息：包含notification字段，后台状态下系统会自动显示通知
• 数据消息：仅包含data字段，后台状态下不会自动弹出通知，需在_firebaseMessagingBackgroundHandler中手动构建通知

确认你发送的是通知消息，而非纯数据消息。如果是数据消息，需按第5点手动处理。

3. 添加ProGuard/R8混淆规则 #

Release模式的混淆可能破坏Firebase通知逻辑，在android/app/proguard-rules.pro中添加：

-keep class com.google.firebase.** { *; }
-keep class io.flutter.plugins.firebase.messaging.** { *; }
-keep class com.google.android.gms.** { *; }

4. 验证AndroidManifest.xml配置 #

确保Manifest中包含必要的服务和权限：

• 添加POST_NOTIFICATIONS权限（Android 13+）：

<uses-permission android:name="android.permission.POST_NOTIFICATIONS" />

• 确认Firebase Messaging服务配置：

<service
    android:name="io.flutter.plugins.firebase.messaging.FlutterFirebaseMessagingService"
    android:exported="false">
    <intent-filter>
        <action android:name="com.google.firebase.MESSAGING_EVENT" />
    </intent-filter>
</service>
<service
    android:name="io.flutter.plugins.firebase.messaging.FlutterFirebaseMessagingBackgroundService"
    android:exported="false"
    android:permission="android.permission.BIND_JOB_SERVICE">
    <intent-filter>
        <action android:name="com.google.firebase.MESSAGING_EVENT" />
    </intent-filter>
</service>

5. 手动在后台handler中显示通知 #

如果发送的是纯数据消息，需借助flutter_local_notifications包手动构建通知：

1. 添加依赖到pubspec.yaml：

flutter_local_notifications: ^16.1.0

2. 修改后台handler：

@pragma('vm:entry-point')
Future<void> _firebaseMessagingBackgroundHandler(RemoteMessage message) async {
  await Firebase.initializeApp();
  print('Handling a background message: ${message.messageId}');

  final FlutterLocalNotificationsPlugin flutterLocalNotificationsPlugin = FlutterLocalNotificationsPlugin();
  const AndroidInitializationSettings initSettingsAndroid = AndroidInitializationSettings('@mipmap/ic_launcher');
  final InitializationSettings initSettings = InitializationSettings(android: initSettingsAndroid);
  await flutterLocalNotificationsPlugin.initialize(initSettings);

  const AndroidNotificationDetails androidDetails = AndroidNotificationDetails(
    'high_importance_channel',
    'High Importance Notifications',
    channelDescription: 'Channel for background notifications',
    importance: Importance.max,
    priority: Priority.high,
    enableVibration: true,
  );
  const NotificationDetails notificationDetails = NotificationDetails(android: androidDetails);

  await flutterLocalNotificationsPlugin.show(
    DateTime.now().millisecondsSinceEpoch ~/ 1000,
    message.data['title'] ?? 'New Notification',
    message.data['body'] ?? 'You have a new message',
    notificationDetails,
  );
}

内容的提问来源于stack exchange，提问作者Afonso Semeano