我目前使用firebase的cloud messaging做推播，訊息可以正常推送，但在ＡＰＰ為背景模式下卻不會進到onBackgroundMessage裏面，只有IOS無法，Android是會執行onBackgroundMessage的，查了很多資料還是無解，要請大家幫幫忙了

main.dart

Future<void> main() async {
  WidgetsFlutterBinding.ensureInitialized();
  FirebaseMessaging.onBackgroundMessage(_firebaseMessagingBackgroundHandler);
  runApp(const App());
}

@pragma('vm:entry-point')
Future<void> _firebaseMessagingBackgroundHandler(
    RemoteMessage message,
    ) async {
  if (kDebugMode) {
    debugPrint('Handling a background message: ${message.messageId}');
  }
}

推播內容
{
"to" : "df9JUN6C1E8Omxez7TINHv:APA91bHZ2SlXU_uSJHQsBck9mc0zsUdgz_lz34DDpiZc0Ck-I2iBazWcNl2V8EZsEGQNt0NRXsP6VDXw79lsxr4MXLVLZOBCRgl6hSrLg88bhj4dMeIVzsoMTXEaE05j3wOyD-7omH2K",
"collapse_key" : "type_a",
"notification" : {
"body" : "Body of Your Notification",
"title": "Title of Your Notification",
"content_available" : true,
"priority" : "high"
},
"data" : {
"body" : "Body of Your Notification in Data",
"title": "Title of Your Notification in Title",
"key_1" : "Value for key_1",
"key_2" : "Value for key_2"
}
}
在ＡＰＰ前景模式下可以打印出content_available為true

info.plist

<key>UIBackgroundModes</key>
	<array>
		<string>fetch</string>
		<string>processing</string>
		<string>remote-notification</string>
	</array>