我一直试图使一个FCM项目与Flutter2-3天。我想，反过来讲我经历的困难会更准确。
首先，我正常地创建了我的项目。然后我用flutterfire cli将Firebase集成到我的项目中。第一个错误是Execution failed for task ':app:mapDebugSourceSetPaths'。出错了。我通过更改GMS版本从x.x.x.10 to x.x.x.15.解决了这个问题
然后我将firebase消息添加到我的项目中，将minSdk错误设置为19并通过。然后，我更新了我的应用程序，以便按照文档中的代码接收后台通知。正确接收第一个通知后，在第二个通知时，应用程序崩溃，FATAL。我再次尝试说，也许这是因为调试模式，但我得到了同样的错误再次，广播接收的消息为第二次。日志一到应用程序就会崩溃。
我的代码和Flutter输出

import 'package:firebase_core/firebase_core.dart';
import 'dart:developer';

import 'package:firebase_messaging/firebase_messaging.dart';
import 'firebase_options.dart';
import 'package:flutter/material.dart';

Future<void> _firebaseMessagingBackgroundHandler(RemoteMessage message) async {
  await Firebase.initializeApp();

  print("Handling a background message: ${message.messageId}");
}

void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  await Firebase.initializeApp(
    options: DefaultFirebaseOptions.currentPlatform,
  );

  FirebaseMessaging.onBackgroundMessage(_firebaseMessagingBackgroundHandler);
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      title: "Simple App",
      theme: ThemeData(
        colorScheme: ColorScheme.fromSeed(seedColor: Colors.blue),
        useMaterial3: true,
        brightness: Brightness.light,
      ),
      home: const MyHomePage(title: 'Simple App'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({super.key, required this.title});

  final String title;

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;

  void showNotification() {
    setState(() {
      _counter++;
    });
  }

  @override
  void initState() {
    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        backgroundColor: Theme.of(context).colorScheme.inversePrimary,
        title: Text(
          "Kimlik Doğrulama Servisi",
          style: TextStyle(fontWeight: FontWeight.bold),
        ),
      ),
      body: Center(
        child: Container()
      ),
    );
  }
}

：：输出：：

D/FLTFireMsgReceiver(19336): broadcast received for message
W/FirebaseMessaging(19336): Unable to log event: analytics library is missing
W/FirebaseMessaging(19336): Missing Default Notification Channel metadata in AndroidManifest. Default value will be used.
D/CompatibilityChangeReporter(19336): Compat change id reported: 160794467; UID 10868; state: ENABLED
I/flutter (19336): Handling a background message: 0:1687133276773552%48e9d64e48e9d64e
W/FirebaseMessaging(19336): Unable to log event: analytics library is missing

D/FLTFireMsgReceiver(19336): broadcast received for message
D/AndroidRuntime(19336): Shutting down VM
E/AndroidRuntime(19336): FATAL EXCEPTION: main
E/AndroidRuntime(19336): Process: com.example.madmin_mobile, PID: 19336
E/AndroidRuntime(19336): java.lang.NullPointerException: Attempt to invoke virtual method 'boolean java.lang.Class.isInterface()' on a null object reference
E/AndroidRuntime(19336):        at java.lang.Class.isAssignableFrom(Class.java:589)
E/AndroidRuntime(19336):        at android.os.Parcel.readParcelableCreatorInternal(Parcel.java:4865)
E/AndroidRuntime(19336):        at android.os.Parcel.readParcelableInternal(Parcel.java:4778)
E/AndroidRuntime(19336):        at android.os.Parcel.readValue(Parcel.java:4544)
E/AndroidRuntime(19336):        at android.os.Parcel.readValue(Parcel.java:4324)
E/AndroidRuntime(19336):        at android.os.Parcel.-$$Nest$mreadValue(Unknown Source:0)
E/AndroidRuntime(19336):        at android.os.Parcel$LazyValue.apply(Parcel.java:4422)
E/AndroidRuntime(19336):        at android.os.Parcel$LazyValue.apply(Parcel.java:4381)
E/AndroidRuntime(19336):        at android.os.BaseBundle.getValueAt(BaseBundle.java:394)
E/AndroidRuntime(19336):        at android.os.BaseBundle.getValue(BaseBundle.java:374)
E/AndroidRuntime(19336):        at android.os.BaseBundle.getValue(BaseBundle.java:357)
E/AndroidRuntime(19336):        at android.os.BaseBundle.get(BaseBundle.java:696)
E/AndroidRuntime(19336):        at android.os.Bundle.getParcelable(Bundle.java:947)
E/AndroidRuntime(19336):        at android.content.Intent.getParcelableExtra(Intent.java:9558)
E/AndroidRuntime(19336):        at io.flutter.plugins.firebase.messaging.FlutterFirebaseMessagingBackgroundExecutor.executeDartCallbackInBackgroundIsolate(FlutterFirebaseMessagingBackgroundExecutor.java:235)
E/AndroidRuntime(19336):        at io.flutter.plugins.firebase.messaging.FlutterFirebaseMessagingBackgroundService.lambda$onHandleWork$0(FlutterFirebaseMessagingBackgroundService.java:146)
E/AndroidRuntime(19336):        at io.flutter.plugins.firebase.messaging.FlutterFirebaseMessagingBackgroundService$$ExternalSyntheticLambda0.run(Unknown Source:4)
E/AndroidRuntime(19336):        at android.os.Handler.handleCallback(Handler.java:942)
E/AndroidRuntime(19336):        at android.os.Handler.dispatchMessage(Handler.java:99)
E/AndroidRuntime(19336):        at android.os.Looper.loopOnce(Looper.java:226)
E/AndroidRuntime(19336):        at android.os.Looper.loop(Looper.java:313)
E/AndroidRuntime(19336):        at android.app.ActivityThread.main(ActivityThread.java:8757)
E/AndroidRuntime(19336):        at java.lang.reflect.Method.invoke(Native Method)
E/AndroidRuntime(19336):        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:571)
E/AndroidRuntime(19336):        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1067)
I/Process (19336): Sending signal. PID: 19336 SIG: 9
Lost connection to device.

让我的应用程序正常工作。