Firebase Push Notification Message using work manager

•  First of all add dependency
  

  implementation("androidx.work:work-runtime-ktx:$work_version:2.9.0")

• Now make class of MyFirebaseMessagingService.kt
  
  import android.app.NotificationChannel
  import android.app.NotificationManager
  import android.app.PendingIntent
  import android.content.Context
  import android.content.Intent
  import android.media.RingtoneManager
  import android.os.Build
  import android.util.Log
  import androidx.core.app.NotificationCompat
  import androidx.work.OneTimeWorkRequest
  import androidx.work.WorkManager
  import androidx.work.Worker
  import androidx.work.WorkerParameters
  import com.example.newnotify.MainActivity
  import com.example.newnotify.R
  import com.google.firebase.messaging.FirebaseMessagingService
  import com.google.firebase.messaging.RemoteMessage
  
  class MyFirebaseMessagingService : FirebaseMessagingService() {
  
      override fun onMessageReceived(remoteMessage: RemoteMessage) {
          super.onMessageReceived(remoteMessage)
  
          if (remoteMessage.data.isNotEmpty()) {
              Log.d(TAG, "Message data payload: ${remoteMessage.data}")
              if (needsToBeScheduled()) {
                  scheduleJob()
              } else {
                  handleNow(remoteMessage)
              }
          }
  
          remoteMessage.notification?.let {
              Log.d(TAG, "Message Notification Body: ${it.body}")
              sendNotification(it.body ?: "")
          }
      }
  
      private fun needsToBeScheduled() = true
  
      override fun onNewToken(token: String) {
          Log.d(TAG, "Refreshed token: $token")
          sendRegistrationToServer(token)
      }
  
      private fun scheduleJob() {
          val work = OneTimeWorkRequest.Builder(MyWorker::class.java).build()
          WorkManager.getInstance(this).enqueue(work)
      }
  
      private fun handleNow(remoteMessage: RemoteMessage) {
          Log.d(TAG, "Short lived task is done.")
          sendNotification(remoteMessage.notification?.body ?: "")
      }
  
      private fun sendRegistrationToServer(token: String?) {
          Log.d(TAG, "sendRegistrationTokenToServer($token)")
      }
  
      private fun sendNotification(messageBody: String) {
          val intent = Intent(this, MainActivity::class.java)
          intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP)
          val pendingIntent = PendingIntent.getActivity(
              this, 0, intent, PendingIntent.FLAG_ONE_SHOT or PendingIntent.FLAG_IMMUTABLE
          )
  
          val channelId = "fcm_default_channel"
          val defaultSoundUri = RingtoneManager.getDefaultUri(RingtoneManager.TYPE_NOTIFICATION)
          val notificationBuilder = NotificationCompat.Builder(this, channelId)
              .setSmallIcon(R.mipmap.ic_launcher)
              .setContentTitle("FCM Message")
              .setContentText(messageBody)
              .setAutoCancel(true)
              .setSound(defaultSoundUri)
              .setPriority(NotificationCompat.PRIORITY_HIGH)
              .setContentIntent(pendingIntent)
  
          val notificationManager = getSystemService(Context.NOTIFICATION_SERVICE) as NotificationManager
  
          if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
              val channel = NotificationChannel(
                  channelId,
                  "Channel human readable title",
                  NotificationManager.IMPORTANCE_DEFAULT
              )
              notificationManager.createNotificationChannel(channel)
          }
  
          val notificationId = 0
          notificationManager.notify(notificationId, notificationBuilder.build())
      }
  
      companion object {
          private const val TAG = "MyFirebaseMsgService"
      }
  
      internal class MyWorker(appContext: Context, workerParams: WorkerParameters) :
          Worker(appContext, workerParams) {
          override fun doWork(): Result {
              // Simulate long-running work here.
              return Result.success()
          }
      }
  }
  
  
  

• In Manifest , make sure you have added permission and service
  
  <uses-permission android:name="android.permission.INTERNET" />
  <uses-permission android:name="android.permission.POST_NOTIFICATIONS" />
  <uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED" />
  <service
      android:name=".messaging.MyFirebaseMessagingService"
      android:exported="true">
      <intent-filter>
          <action android:name="com.google.firebase.MESSAGING_EVENT"/>
      </intent-filter>
  </service>
  

• Boom !! You'll get notifications.