Custom sound in Firebase push notification

I am sending push notification from Firebase to my Android application, but it is only playing the default sound when the notification is recieved.

I have set the custom sound param {“sound”:”notificationsound.mp3”} in the fcm notification object and the file is present in the res/raw folder according to (https://firebase.google.com/docs/cloud-messaging/http-server-ref)
But It’s still playing the default sound on all app states (background, foreground and killed).
This is my request body for sending the notification on Android :

{
"to" : “some id”,
"notification": {
"title":"asdasd",
"body":"sdsad",
"click_action" : "MAIN",
"sound":"notificationsound.mp3"
},
"data": {
"title" : "Something",
"body" : "Important",
"type" : "message"
},
"priority": "high"
}

What I can do to play the custom notification sound.

I was also looking for the solution to custom sound for firebase notification in the android, And I have solved this problem through Notification Channel.

I have created one notification channel with custom sound, that sound plays after receiving notification in the application background state.

You can refer following links of the notification channel.

https://medium.com/exploring-android/exploring-android-o-notification-channels-94cd274f604c

https://developer.android.com/training/notify-user/channels

You need to put your mp3 file at /res/raw/ path.

Please find the code.

NotificationManager notificationManager = (NotificationManager) getActivity().getSystemService(NotificationManager.class); // If you are writting code in fragment

OR

NotificationManager notificationManager = (NotificationManager) getSystemService(NotificationManager.class); // If you are writting code in Activity

createNotificationChannel function

private void createNotificationChannel() { 
 Uri sound = Uri.parse(ContentResolver.SCHEME_ANDROID_RESOURCE + "://" + context.getPackageName() + "/" + R.raw.sample); //Here is FILE_NAME is the name of file that you want to play 
// Create the NotificationChannel, but only on API 26+ because 
// the NotificationChannel class is new and not in the support library if 
(Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) 
 { 
    CharSequence name = "mychannel"; 
    String description = "testing"; 
    int importance = NotificationManager.IMPORTANCE_DEFAULT; 
    AudioAttributes audioAttributes = new AudioAttributes.Builder() 
     .setContentType(AudioAttributes.CONTENT_TYPE_SONIFICATION) 
     .setUsage(AudioAttributes.USAGE_ALARM) 
     .build(); 
   NotificationChannel channel = new NotificationChannel("cnid", name, importance); 
   channel.setDescription(description); 
   channel.enableLights(true); channel.enableVibration(true); 
   channel.setSound(sound, audioAttributes); 
   notificationManager.createNotificationChannel(channel); 
  } 
};

createNotificationChannel(); 

To achieve this you need to pass android_channel_id property in the firebase notification request object.

{
 "notification": {
 "body": "this is testing notification",
 "title": "My App",
 "android_channel_id": "cnid"
 },
 "to": "token"
}