Flutter FirebaseMessaging onBackgroundMessage空值检查操作符

Question

我正在构建一个带有推送通知的firebase应用程序，因此该应用程序正在运行，但在我使用"flutter clean"如果不更改代码

，则会出现此错误。

E/flutter (14812): [ERROR:flutter/lib/ui/ui_dart_state.cc(209)] Unhandled Exception: Null check operator used on a null value
E/flutter (14812): #0      MethodChannelFirebaseMessaging.registerBackgroundMessageHandler (package:firebase_messaging_platform_interface/src/method_channel/method_channel_messaging.dart:180:53)
E/flutter (14812): #1      FirebaseMessagingPlatform.onBackgroundMessage= (package:firebase_messaging_platform_interface/src/platform_interface/platform_interface_messaging.dart:102:16)
E/flutter (14812): #2      FirebaseMessaging.onBackgroundMessage (package:firebase_messaging/src/messaging.dart:73:31)
E/flutter (14812): #3      main (package:mitaa/main.dart:37:21)

firebase_messaging: ^11.2.6

Answer 1

https://firebase.flutter.dev/docs/messaging/usage/

    Future<void> _firebaseMessagingBackgroundHandler(RemoteMessage message) async {
  // If you're going to use other Firebase services in the background, such as Firestore,
  // make sure you call `initializeApp` before using other Firebase services.
  await Firebase.initializeApp();
  print("Handling a background message: ${message.messageId}");
}
void main() {
  FirebaseMessaging.onBackgroundMessage(_firebaseMessagingBackgroundHandler);
  runApp(MyApp());
}

引用