Enabling background messagin (cloud messaging), documentation

[amir2202]

I have tried to use the background capabilities of firebase_messaging, to allow processing messages when the app is not in the foreground. However this causes problems I followed the instructions as in the screenshot below.

For my project the main package resides within kotlin. Thus the project structure is .../app/src/main ,where there are both kotlin and java folders. The mainactivity resides within the kotlin class, thus when adding an application class, I did this here as instructed, as kotlin and java have interoperability, I simply converted the class to kotlin and it is as follows.

package com.dating
import io.flutter.app.FlutterApplication
import io.flutter.plugin.common.PluginRegistry
import io.flutter.plugin.common.PluginRegistry.PluginRegistrantCallback
import io.flutter.plugins.GeneratedPluginRegistrant
import io.flutter.plugins.firebasemessaging.FlutterFirebaseMessagingService

class Application : FlutterApplication(), PluginRegistrantCallback {
  override fun onCreate() {
    super.onCreate()
    FlutterFirebaseMessagingService.setPluginRegistrant(this)
  }

  override fun registerWith(registry:PluginRegistry) {
    GeneratedPluginRegistrant.registerWith(registry)
  }
}

This however yields the following error
C:\Users\amir2\AndroidStudioProjects\dating\android\app\src\main\kotlin\com\dating\Application.kt: (16, 48): Type mismatch: inferred type is PluginRegistry but FlutterEngine was expected and fails compilation within 3 seconds, I have updated the manifest as instructed as well, and set the name to .Application

After further digging, i even tried to change the structure to java, so no kotlin use now, this didnt change anything as i thought. The example code provided i assume has errors as public final class GeneratedPluginRegistrant { public static void registerWith(@NonNull FlutterEngine flutterEngine) {. The example code provided wants to provide a type of PluginRegistry to a function which takes a FlutterEngine type. This is a mistake in the example provided on the https://pub.dev/packages/firebase_messaging documentation for when enabling background messaging.
I do not know still how to enable this appropriately then.

[darshankawar]

Hi @amir2202,
There's similar open issue describing your case, 1684.
Please follow-up there for updates and any questions.
Closing this as duplicate.