E/扑动(2363)：[错误：flutter/runtime/dart_vm_initializer.cc(41)]无法处理的异常：用于空值的空校验运算符

c9x0cxw0 于 2023-09-28 发布在 Flutter

关注(0)|答案(2)|浏览(201)

我试图在BackgroundMessage上初始化Firebase消息传递，但出现了一个非常不寻常的错误。我尝试了所有我知道的方法，但发现错误仍然存在。

Future<void> handleBackgroundMessage(RemoteMessage message) async {
final notification = message.notification;

if (notification != null) {
  print("title: ${notification.title}");
  print("body: ${notification.body}");
} else {
  print("No notification data found in the message.");
}

final data = message.data;

print("payload: $data");
}

这就是我调用handleBackgroundMessage的地方

Future<void> initNotification() async {
try {
  await _firebaseMessaging.requestPermission();

  final fcmToken = await _firebaseMessaging.getToken();
  await _firebaseMessaging.subscribeToTopic("Church");

  print(fcmToken);

  FirebaseMessaging.onBackgroundMessage(handleBackgroundMessage);
} catch (e) {
  print("Error initializing notifications: $e");
}
}

这是我在主函数中初始化firebase的地方

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

  runApp(const MainApp());
}

这是我得到的错误

Restarted application in 7,630ms.
W/kiibati.kiibat( 2363): Accessing hidden method Ldalvik/system/CloseGuard;->close()V (greylist,core-platform-api, linking, allowed)
W/kiibati.kiibat( 2363): Accessing hidden method Ldalvik/system/CloseGuard;->warnIfOpen()V (greylist,core-platform-api, linking, allowed)
I/flutter ( 2363): c14bRHbiQtmVpfJ5RlOpng:APA91bFm5XYVPU4CvICaNb8oFkYWw80T7ZK1RehffDPgna59WxX1nWRzEFSltY7mH4cBRrpmb07ZMZNKY0g3TrlbnclGG8oqn8XGL8oL8SzhOCUR8r1dCpW1H6qBzxVztj4mJi3p7Sne
E/flutter ( 2363): [ERROR:flutter/runtime/dart_vm_initializer.cc(41)] Unhandled Exception: Null check operator used on a null value
E/flutter ( 2363): #0      MethodChannelFirebaseMessaging.registerBackgroundMessageHandler
method_channel_messaging.dart:181
E/flutter ( 2363): #1      FirebaseMessagingPlatform.onBackgroundMessage=
platform_interface_messaging.dart:102
E/flutter ( 2363): #2      FirebaseMessaging.onBackgroundMessage
messaging.dart:73
E/flutter ( 2363): #3      FirebaseApi.initNotification
firebaseapi.dart:17
E/flutter ( 2363): <asynchronous suspension>
E/flutter ( 2363): #4      main
main.dart:23
E/flutter ( 2363): <asynchronous suspension>
E/flutter ( 2363):
D/SharedPreferencesImpl( 2363): Time required to fsync /data/user/0/com.kiibati.kiibati/shared_prefs/com.google.android.gms.appid.xml: [<1: 0, <2: 0, <4: 0, <8: 1, <16: 2, <32: 0, <64: 0, <128: 0, <256: 0, <512: 1, <1024: 0, <2048: 0, <4096: 0, <8192: 0, <16384: 0, >=16384: 0]
W/DynamiteModule( 2363): Local module descriptor class for com.google.android.gms.providerinstaller.dynamite not found.
I/DynamiteModule( 2363): Considering local module com.google.android.gms.providerinstaller.dynamite:0 and remote module com.google.android.gms.providerinstaller.dynamite:0
W/ProviderInstaller( 2363): Failed to load providerinstaller module: No acceptable module com.google.android.gms.providerinstaller.dynamite found. Local version is 0 and remote version is 0.
D/FLTFireMsgReceiver( 2363): broadcast received for message
W/FLTFireMsgService( 2363): A background message could not be handled in Dart as no onBackgroundMessage handler has been registered.
W/FirebaseMessaging( 2363): Unable to log event: analytics library is missing
W/FirebaseMessaging( 2363): Missing Default Notification Channel metadata in AndroidManifest. Default value will be used.

dart

来源：https://stackoverflow.com/questions/77126652/e-flutter-2363-errorflutter-runtime-dart-vm-initializer-cc41-unhandled

2条答案

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lymgl2op1#

好的，请将你的代码还原成这样：

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

 FirebaseMessaging.onBackgroundMessage(handleBackgroundMessage);
}

//your handleBackgroundMessage let it just do this
Future<void> handleBackgroundMessage(RemoteMessage message) async {
  await Firebase.initializeApp();
}

//Handle all your print statements in the `initState`
...
initSate(){
 super.initState();

///Listen to foreground notification
    FirebaseMessaging.onMessage.listen((RemoteMessage message) {
      RemoteNotification? notification = message.notification;
      AndroidNotification? android = message.notification?.android;
      if (notification != null && android != null) {
        flutterLocalNotificationsPlugin.show(
          notification.hashCode,
          notification.title,
          notification.body,
          NotificationDetails(
            android: AndroidNotificationDetails(
              channel.id,
              channel.name,
              channelDescription: channel.description,
              //color: Colors.blue,
              icon: "@drawable/ic_notification",
            ),
          ),

        );

      }
    });
    
    
    ///Background but not terminated
    FirebaseMessaging.onMessageOpenedApp.listen((RemoteMessage message) {

      RemoteNotification? notification = message.notification;
      AndroidNotification? android = message.notification?.android;
      ///promotion notification
      if (notification != null && android != null && message.data['type'] =='Promotion' || message.data['type'] =='promotion') {
         //navigate somewhere or print
      }
      else {
        //navigate somewhere
      }
    });
}
...

//You do not need this anymore
Future<void> initNotification() async {
try {
  await _firebaseMessaging.requestPermission();

  final fcmToken = await _firebaseMessaging.getToken();
  await _firebaseMessaging.subscribeToTopic("Church");

  print(fcmToken);

  FirebaseMessaging.onBackgroundMessage(handleBackgroundMessage);
} catch (e) {
  print("Error initializing notifications: $e");
}
}

这是从我的代码请更换所有的变量，以您的喜好

赞(0）回复(0）举报 2023-09-28

dfty9e192#

错误“Unhandled Exception：Null check operator used on a null value”表示您正尝试对为null的变量使用null check operator。在本例中，似乎是在尝试使用FirebaseMessaging.onBackgroundMessage（默认BackgroundMessage）注册后台消息处理程序时出现问题。
若要解决此问题，应确保确实定义了handleBackgroundMessage，并且不为null。另外，请确保正确配置了FirebaseMessaging的导入和初始化。以下是一些步骤：
确保在Dart文件中正确导入了FirebaseMessaging：

import 'package:firebase_messaging/firebase_messaging.dart';

确保您已在main或应用的入口点初始化FirebaseMessaging：

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

验证handleBackgroundMessage函数是否定义正确且没有任何错误：

Future<void> handleBackgroundMessage(RemoteMessage message) async {
  final notification = message.notification;

  if (notification != null) {
    print("title: ${notification.title}");
    print("body: ${notification.body}");
  } else {
    print("No notification data found in the message.");
  }

  final data = message.data;

  print("payload: $data");
}

确保适当地调用了initNotification函数。检查函数调用序列是否存在任何问题，并确保Firebase配置正确。希望这有助于解决问题。
如果执行这些步骤后问题仍然存在，您可能需要检查您正在使用的Firebase Messaging版本，以确保它是最新的，并且与您正在使用的Flutter版本兼容。

赞(0）回复(0）举报 2023-09-28

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E/扑动(2363)：[错误：flutter/runtime/dart_vm_initializer.cc(41)]无法处理的异常：用于空值的空校验运算符

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