使用Flutter Local Notification+FCM时后台/终止状态下通知不显示

1. 补全Flutter Local Notifications插件初始化流程 #

你的代码仅定义了安卓初始化配置，但未完成插件的初始化操作，这是后台/终止状态下无法显示通知的核心原因之一。修改main函数，补充初始化步骤：

Future<void> main() async {
  WidgetsFlutterBinding.ensureInitialized();

  await _configureLocalTimeZone();

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

  await FirebaseMessaging.instance.subscribeToTopic('debug');

  // --- 新增插件初始化逻辑 ---
  const AndroidInitializationSettings initializationSettingsAndroid =
      AndroidInitializationSettings('ic_stat_notification');
  const InitializationSettings initializationSettings =
      InitializationSettings(android: initializationSettingsAndroid);
  await flutterLocalNotificationsPlugin.initialize(initializationSettings);
  // --- 初始化逻辑结束 ---

  final NotificationAppLaunchDetails? notificationAppLaunchDetails = !kIsWeb &&
          Platform.isLinux
      ? null
      : await flutterLocalNotificationsPlugin.getNotificationAppLaunchDetails();
  String initialRoute = HomePage.routeName;
  if (notificationAppLaunchDetails?.didNotificationLaunchApp ?? false) {
    selectedNotificationPayload =
        notificationAppLaunchDetails!.notificationResponse?.payload;
    initialRoute = SecondPage.routeName;
  }

  runApp(
    MaterialApp(
      initialRoute: initialRoute,
      routes: <String, WidgetBuilder>{
        HomePage.routeName: (_) => HomePage(notificationAppLaunchDetails),
        SecondPage.routeName: (_) => SecondPage(selectedNotificationPayload)
      },
    ),
  );
}

2. 调整FCM消息类型，触发后台处理器 #

应用处于后台/终止状态时：

• 仅包含notification字段的纯通知消息会由系统直接展示，不会触发firebaseMessagingBackgroundHandler
• 必须发送仅包含data字段的数据消息，或同时包含notification和data字段并配置click_action: FLUTTER_NOTIFICATION_CLICK（安卓），才能触发后台处理器

示例数据消息结构（发送时使用）：

{
  "to": "/topics/debug",
  "data": {
    "title": "big text title",
    "body": "silent body",
    "bigText": "Lorem ipsum dolor sit amet, consectetur adipiscing elit..."
  }
}

之后在后台处理器中从message.data提取字段，动态构建通知内容，避免写死固定文本。

3. 优化后台处理器的通知调用逻辑 #

确保flutterLocalNotificationsPlugin是全局实例，同时优化通知ID的生成逻辑，避免后台环境中ID重置问题：

@pragma('vm:entry-point')
Future<void> firebaseMessagingBackgroundHandler(RemoteMessage message) async {
  await Firebase.initializeApp(
    options: DefaultFirebaseOptions.currentPlatform,
  );
  print('A Background message just showed up :  ${message.messageId}');

  // 从data字段提取动态内容
  final String title = message.data['title'] ?? 'Default Title';
  final String body = message.data['body'] ?? 'Default Body';
  final String bigText = message.data['bigText'] ?? 'Default Big Text';

  const BigTextStyleInformation bigTextStyleInformation =
      BigTextStyleInformation(
    bigText,
    htmlFormatBigText: true,
    contentTitle: 'News Shot notification',
    htmlFormatContentTitle: true,
    summaryText: 'summary text',
    htmlFormatSummaryText: true,
  );

  AndroidNotificationDetails androidNotificationDetails =
      AndroidNotificationDetails(
    'big text channel id', 
    'big text channel name',
    channelDescription: 'big text channel description',
    styleInformation: bigTextStyleInformation,
    importance: Importance.max,
    priority: Priority.high, // 确保后台状态下通知能正常弹出
  );
  NotificationDetails notificationDetails =
      NotificationDetails(android: androidNotificationDetails);
  
  // 使用消息ID作为通知ID，避免重复或重置问题
  await flutterLocalNotificationsPlugin.show(
      int.tryParse(message.messageId ?? '0') ?? 0, title, body, notificationDetails);
}

4. 检查安卓Manifest配置 #

• 添加Android 13+所需的通知权限：

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

• 配置默认通知通道，避免因通道缺失导致通知不显示：

<application ...>
  <meta-data
      android:name="com.google.firebase.messaging.default_notification_channel_id"
      android:value="big text channel id" /> <!-- 与代码中使用的通道ID保持一致 -->
</application>

验证步骤 #

1. 先测试前台状态下发送数据消息，确认后台处理器被调用、本地通知正常显示
2. 再测试后台/终止状态，发送相同的数据消息，检查终端日志是否打印A Background message just showed up，并确认通知显示

内容的提问来源于stack exchange，提问作者austin