FCM notification message are not received in android Oreo version?

Question

I have send FCM notification from server to users. It works fine(until api 25) but in Oreo when the application have not in background(services are closed) (or) completely close

Answer 1

"Starting in Android 8.0 (API level 26), all notifications must be assigned to a channel or it will not appear."

Individual notifications must now be put in a specific channel. (Reference)

Option 1 [simple] Change the target android version Android 7.1 (API level 25) or lower.

compileSdkVersion 25
    defaultConfig {
        applicationId "com.fcm"
        minSdkVersion 16
        targetSdkVersion 25
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    }

Option 2 If you don't want to change the target version then follow the following method

if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
     NotificationManager nm = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
     NotificationChannel nc = new NotificationChannel(“[enter your product id]”, “[Name]”,NotificationManager.IMPORTANCE_MAX);
     nc.setDescription(“[your description for the notification]”);
     nc.enableLights(true);
     nc.setLightColor(Color.GREEN);
     nm.createNotificationChannel(nc);
  }

Use following Builder constructor

NotificationCompat.Builder notificationBuilder = new NotificationCompat.Builder(appContext, [id you mentioned above in constructor of NotificationChannel])

Create the notification from the Builder

nm.notify("0", notificationBuilder.build())