为什么Flutter Workmanager显示错误：“无法解决主入口点函数”和多个Flutterjni警告？

Question

问题：

我正在尝试在我的Flutter应用中实现背景任务，以在使用Workmanager在线时添加用户在线数据库。但是，在启动工人管理器并运行应用程序后，我在日志中遇到了此错误：

Software配置：

Java：17.0.11
扑来：3.29.0
Android Studio：2024.2.1补丁3

Error日志：

: FlutterJNI.loadLibrary called more than once
I/ResourceExtractor(13363): Found extracted resources res_timestamp-1-1741615888564
W/FlutterJNI(13363): FlutterJNI.prefetchDefaultFontManager called more than once
W/FlutterJNI(13363): FlutterJNI.init called more than once
E/flutter (13363): [ERROR:flutter/runtime/dart_isolate.cc(869)] Could not resolve main entrypoint function.
E/flutter (13363): [ERROR:flutter/runtime/dart_isolate.cc(170)] Could not run the run main Dart entrypoint.
E/flutter (13363): [ERROR:flutter/runtime/runtime_controller.cc(557)] Could not create root isolate.
E/flutter (13363): [ERROR:flutter/shell/common/shell.cc(668)] Could not launch engine with configuration.
I/Choreographer(13363): Skipped 74 frames!  The application may be doing too much work on its main thread.
I/flutter (13363): Initializing WorkManager...
I/flutter (13363): WorkManager initialized successfully.
I/flutter (13363): 📂 List of Databases:
I/flutter (13363): 📌 Database Found: /data/user/0/com.example.test_app/app_flutter/app.db
I/flutter (13363): Users in database:
I/flutter (13363): ID: 1, Name: raj, Job: worker, Synced: false
I/flutter (13363): ID: 2, Name: robjn, Job: seeker, Synced: false
I/flutter (13363): ID: 3, Name: Raj, Job: Engineer, Synced: false
I/flutter (13363): ID: 4, Name: Raj, Job: Engineer, Synced: false
I/flutter (13363): ID: 5, Name: Raj, Job: Engineer, Synced: false
I/flutter (13363): ID: 6, Name: Raj, Job: Engineer, Synced: false
I/flutter (13363): ID: 7, Name: Raj, Job: Engineer, Synced: false
I/flutter (13363): ID: 8, Name: Raj, Job: Engineer, Synced: false
I/flutter (13363): ID: 9, Name: Ravi, Job: Tailor, Synced: false
I/flutter (13363): ID: 10, Name: Ragul, Job: Sailor, Synced: false

我的代码是我的代码：

main.dart

void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  await WorkManagerService.initialize();
  final database = AppDatabase();
  await database.listAllDatabases();
  final users = await database.getAllUsers();
  print("Users in database:");
  for (var user in users) {
    print(
        "ID: ${user.id}, Name: ${user.name}, Job: ${user.job}, Synced: ${user.isSynced}");
  }
  runApp(const ProviderScope(child: MyApp()));
}

testadDuserProvider.dart

final addTestUserProvider =
    StateNotifierProvider<AddTestUserProvider, AsyncValue<User?>>((ref) {
  final database = ref.watch(databaseProvider);
  return AddTestUserProvider(database);
});

class AddTestUserProvider extends StateNotifier<AsyncValue<User?>> {
  final AppDatabase _database;

  AddTestUserProvider(this._database) : super(const AsyncValue.data(null));

  Future<void> addUser(String name, String job, bool bool) async {
    state = const AsyncValue.loading();
    print("offline");
    await _addUserOffline(name, job);
  }

  Future<void> _addUserOffline(String name, String job) async {
    try {
      final newUser = UsersCompanion(
        name: Value(name),
        job: Value(job),
        isSynced: const Value(false),
      );
      await _database.insertUser(newUser);
      WorkManagerService.registerSyncTask();
      state = const AsyncValue.data(null);
    } catch (e, stackTrace) {
      state = AsyncValue.error(e, stackTrace);
    }
  }
}

Work_manager.dart

import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'package:workmanager/workmanager.dart';

import '../data/providers/user_provider.dart';
import '../database/app_database.dart';
import '../utils/constants.dart';
import 'api_service.dart';
import 'network_service.dart';

const String syncTask = "sync_offline_users";

class WorkManagerService {
  static Future<void> initialize() async {
    print("Initializing WorkManager...");
    Workmanager().initialize(
      _callbackDispatcher,
      isInDebugMode: true,
    );
    print("WorkManager initialized successfully.");
  }

  static void registerSyncTask() {
    print("Registering sync task...");
    Workmanager().registerOneOffTask(
      "sync_users_task",
      syncTask,
      constraints: Constraints(
        networkType: NetworkType.connected,
      ),
    );
    print("Sync task registered successfully.");
  }

  @pragma('vm:entry-point')
  static void _callbackDispatcher() {
    Workmanager().executeTask((task, inputData) async {
      print("Executing task: $task");
      final container = ProviderContainer();

      try {
        final database = container.read(databaseProvider);
        final apiService = container.read(apiServiceProvider);
        final isConnected =
            container.read(connectivityServiceProvider).isConnectedSync();

        if (task == syncTask && isConnected) {
          await _syncOfflineUsers(database, apiService);
        }
      } catch (e) {
        print("Error in callback dispatcher: $e");
      } finally {
        container.dispose();
      }

      return Future.value(true);
    });
  }

  static Future<void> _syncOfflineUsers(
      AppDatabase database, ApiService apiService) async {
    print("Starting to sync offline users...");
    final unsyncedUsers = await database.getUnsyncedUsers();
    print("Fetched ${unsyncedUsers.length} unsynced users.");

    for (var user in unsyncedUsers) {
      print("Syncing user: ${user.name} (ID: ${user.id})");
      try {
        final response = await apiService.post(
          addUsersEndpoint,
          body: {"name": user.name, "job": user.job},
        );
        print("API response received: $response");

        if (response != null && response['id'] != null) {
          print(
              "User ${user.name} synced successfully with ID: ${response['id']}");
          await database.markUserAsSynced(user.id, response['id']);
          print("User marked as synced in the database.");
        } else {
          print(
              "API response is null or missing ID. Sync failed for user ${user.id}.");
        }
      } catch (e) {
        print("Failed to sync user ${user.id}: $e");
      }
    }

    print("Offline user sync completed.");
  }
}

androidmanifest.xml

  <uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED"/>
  <meta-data
            android:name="flutterEmbedding"
            android:value="2" />
  <service android:name="MyJobService"
            android:permission="android.permission.BIND_JOB_SERVICE"
            android:exported="true">
        </service>

如果您想在自己的系统中运行此项目以进行详细分析。尝试此回购：

github

步骤：

使用test_screen.dart和test_provider用于重新创建此问题，我将逻辑分开以节省逻辑。

1. 错误之所以发生错误，是因为Workmanager的背景回调函数必须是顶级函数，而不是类内部的静态方法 - 即使是用
Could not resolve main entrypoint function

注释。在您的代码中，

Answer 1

被定义为

_callbackDispatcher

中的静态方法，尽管它标有适当的pragma，但Workmanager无法将其定位在后台隔离中。

要解决此问题，您需要移出课堂，并将其定义为文件中的独立顶级功能。这样，当背景隔离启动时，它可以可靠地查找并执行回调函数。通常，多种初始化调用（例如，当firbase.initializeapp被称为两次），是一个单独的问题。但是，通过使您的回调成为顶级功能来解决入口点问题，应消除可防止引擎在后台隔离中启动的致命错误。