I\'m trying Firebase-Notification API the service is worked perfect when i send downstream message from console to app, but how to send message to topic registered users ? <
This is an alternate path.
If you subscribe a client app to an unexisting topic then the topic will also be created without having to call any firebase url request.
It' will also take a couple of hours to appear on Firebase Console.
By using google shared example: https://github.com/firebase/quickstart-android/tree/master/messaging you can confirm the same.
FirebaseMessaging.getInstance().subscribeToTopic("news");
Log.d(TAG, "Subscribed to news topic");