flutter_background_service_Android插件在安卓设备抛出主隔离区使用异常

我正在开发一款使用flutter_background_service包实现后台服务的Flutter应用，集成flutter_background_service_Android插件后，安卓设备上的后台服务无法正常运行，抛出如下异常：

flutter_background_service_android threw an error: Exception: This class should only be used in the main isolate (UI App). The app may not function as expected until you remove this plugin from pubspec.yaml

以下是我的后台服务实现代码（my_background_service.dart）：

// ignore_for_file: avoid_print

import 'dart:async';
import 'dart:io';
import 'dart:ui';
import 'package:flutter/material.dart';
import 'package:flutter_background_service/flutter_background_service.dart';
import 'package:flutter_background_service_android/flutter_background_service_android.dart';
import 'package:flutter_local_notifications/flutter_local_notifications.dart';
import 'package:intl/intl.dart';
import 'package:shared_preferences/shared_preferences.dart';

import '/helper/my_helper/socket_io_helper.dart';
import '/helper/my_helper/my_get_di.dart' as my_di;

/// Initialization of the Background Service
Future<void> initializeBackgroundService() async {
  final service = FlutterBackgroundService();

  /// OPTIONAL, using custom notification channel id
  const AndroidNotificationChannel channel = AndroidNotificationChannel(
    'my_foreground',
    'MY FOREGROUND SERVICE',
    description: 'This channel is used for important notifications.',
    importance: Importance.low,
  );

  /// Object of the FlutterLocalNotificationsPlugin
  final FlutterLocalNotificationsPlugin flutterLocalNotificationsPlugin =
      FlutterLocalNotificationsPlugin();

  /// Initialize settings
  if (Platform.isIOS || Platform.isAndroid) {
    await flutterLocalNotificationsPlugin.initialize(
      const InitializationSettings(
        iOS: DarwinInitializationSettings(),
        android: AndroidInitializationSettings('ic_bg_service_small'),
      ),
    );
  }

  /// Create android notification channel
  await flutterLocalNotificationsPlugin
      .resolvePlatformSpecificImplementation<
          AndroidFlutterLocalNotificationsPlugin>()
      ?.createNotificationChannel(channel);

  /// Configuration of the Background Service
  await service.configure(
    androidConfiguration: AndroidConfiguration(
      onStart: onStart,
      autoStart: true,
      isForegroundMode: true,
      notificationChannelId: 'my_foreground',
      initialNotificationTitle: 'AWESOME SERVICE',
      initialNotificationContent: 'Initializing',
      foregroundServiceNotificationId: 888,
    ),
    iosConfiguration: IosConfiguration(
      autoStart: true,
      onForeground: onStart,
      onBackground: onIosBackground,
    ),
  );

  /// Starting the background service after doing the configurations
  service.startService();
}

// DOLATER: Handle the iOS Background Task Here
@pragma('vm:entry-point')
Future<bool> onIosBackground(ServiceInstance service) async {
  WidgetsFlutterBinding.ensureInitialized();
  DartPluginRegistrant.ensureInitialized();
  return true;
}

@pragma('vm:entry-point')
void onStart(ServiceInstance service) async {
  DartPluginRegistrant.ensureInitialized();

  /// OPTIONAL when use custom notification
  final FlutterLocalNotificationsPlugin flutterLocalNotificationsPlugin =
      FlutterLocalNotificationsPlugin();

  if (service is AndroidServiceInstance) {
    service.on('setAsForeground').listen((event) {
      service.setAsForegroundService();
    });

    service.on('setAsBackground').listen((event) {
      service.setAsBackgroundService();
    });
  }

  service.on('stopService').listen((event) {
    service.stopSelf();
  });

  /// My instances
  SocketIoHelper socketIoHelper = SocketIoHelper();

  /// Executed when the app is in the foreground
  service.on('loginSuccess').listen((event) async {
    /// Creating a socket.io client
    await my_di.init();
    await socketIoHelper.initializeAwesomeNotification();
    await socketIoHelper.initializeMsgService();
    await socketIoHelper.createTopics();
  });
  service.on('containsTheTopics').listen((event) async {
    await socketIoHelper.joinCallInitializationTopic();
    await socketIoHelper.listenCallInitializationTopic();
    await socketIoHelper.listenCallRecieveTopic();
  });

  /// Executed when the app is in the background
  final prefs = await SharedPreferences.getInstance();
  final plusRemovedPhoneNumberFromLocal =
      prefs.getString("plusRemovedPhoneNumber") ?? "";

  /// Creating a socket.io client
  if (plusRemovedPhoneNumberFromLocal != "") {
    await my_di.init();
    await socketIoHelper.initializeAwesomeNotification();
    await socketIoHelper.initializeMsgService();
    await socketIoHelper.joinCallInitializationTopic();
    await socketIoHelper.listenCallInitializationTopic();
    await socketIoHelper.listenCallRecieveTopic();
  }

  /// Update the background service timer
  /// And show it as a foreground notification
  Timer.periodic(const Duration(seconds: 1), (timer) async {
    if (service is AndroidServiceInstance) {
      if (await service.isForegroundService()) {
        flutterLocalNotificationsPlugin.show(
          888,
          'COOL SERVICE',
          'Awesome ${DateTime.now()}',
          const NotificationDetails(
            android: AndroidNotificationDetails(
              'my_foreground',
              'MY FOREGROUND SERVICE',
              icon: 'ic_bg_service_small',
              ongoing: true,
            ),
          ),
        );

        /// if you don't using custom notification, uncomment this
        service.setForegroundNotificationInfo(
          title: "My Service",
          content: "",
        );
      }
    }

    /// Printing background service timer in the flutter terminal
    print(
        "📗 Background Service ====> ${DateFormat('yyyy-MM-dd hh:mm:ss').format(DateTime.now())} 📗");
  });
}

问题原因与解决方案 #

原因

异常提示明确说明flutter_background_service_Android的类只能在**主隔离（UI线程）**中使用，而你的后台服务入口函数onStart被标记为@pragma('vm:entry-point')，运行在单独的后台隔离中，在此环境下加载该插件的类会触发异常。

解决步骤

1. 移除后台服务代码中的插件导入
   从my_background_service.dart中删除以下导入语句：

   import 'package:flutter_background_service_android/flutter_background_service_android.dart';
   

   你代码中用到的AndroidServiceInstance类型判断属于flutter_background_service核心包的功能，不需要额外导入flutter_background_service_Android即可使用。

2. 确认插件仅在主隔离中使用
   如果需要调用flutter_background_service_Android提供的扩展API（比如高级安卓后台配置），确保这些代码只在主隔离（UI层）执行，不要放到后台服务的onStart函数中。

3. 重新运行项目
   移除导入后重新编译运行，后台服务即可正常启动。

内容的提问来源于stack exchange，提问作者Chanaka