How do I specify the recipient token when using RemoteMessage of Firebase Cloud Messaging?

Question

I am trying to establish push notifications in my app for certain actions ("someone liked your this", "someone commented on that" etc).

I tried to follow google's guide here

But when I copied the code, this part of it

String response = FirebaseMessaging.getInstance().send(message);

Gave an error saying it is expecting a RemoteMessage and not Message . I am trying to change it to RemoteMessage, but I can't understand:

1. Where do I specify the token of the recipient? I cant find an equivalent to .setToken .
2. What to put inside the brackets of RemoteMessage.Builder()

I've been going through a lot of manuals but I can't find any that address it. Is it a new change in the API?

The best way to help me would be an example with Kotlin of a new generated message - one that in response would trigger a new push notification for the recipient, based on the token (I'm pretty sure I can handle the receiving by myself).

Thank you!

Edit:

I was able to make it fit the pattern it would be happy with, but I can't get the notifications to show up.

This is the function I am using to send the notification:

 fun sendCloudMessage(userId: String) {

        val receiverRef = FirebaseDatabase.getInstance().getReference("/users/$userId/services/firebase-token")

        receiverRef.addListenerForSingleValueEvent(object : ValueEventListener {
            override fun onCancelled(p0: DatabaseError) {

            }

            override fun onDataChange(p0: DataSnapshot) {

                val registrationToken = p0.getValue(String::class.java)

                Log.d("tokencomplete", p0.toString())
                Log.d("tokenonly", registrationToken)

                val fm = FirebaseMessaging.getInstance()

                fm.send(
                    RemoteMessage.Builder("$registrationToken@gcm.googleapis.com")
                        .setMessageId(Integer.toString(0))
                        .addData("my_message", "Hello World")
                        .addData("my_action", "SAY_HELLO")
                        .build()
                )
            }

        })

    }

The userId the I pass to this function is the firebase uid, and using that I fetch the most recent token of the app the user is using. I've checked and that part works and I get in return the token in a format similar to this

ecK86WRoAh4:APA91bGQWSesCptPF_nzfkmgDe-zOYYo2Cj4XT_NeNTVaBxQakbvauOpkVFd7DCRIugMCfso5SadEUtyTRvrhdCiBpKxGGMRgUYNsUhA24f9IkmxjL5dWD

But the function itself doesn't spark any notification in the other device (I am using two devices trying to get one to spark a notification with the other).

Answer 1

Set the sender id in your RemoteMessage builder constructor, it should look like this:

RemoteMessage.Builder(token) ;

edit

here is the method im using:

public void sendMessage (final String data) {
FirebaseMessaging fm = FirebaseMessaging.getInstance();

String token = FirebaseInstanceId.getInstance().getToken();
String msgID = DigestUtils.sha1Hex(token + System.currentTimeMillis());
String SENDER_ID = "someID";

RemoteMessage.Builder RMBuilder =
new RemoteMessage.Builder(SENDER_ID + "@gcm.googleapis.com");
RMBuilder.setMessageId(msgID);

Map<String, Object> mapData = Utils.jsonToMap(data);

for (Map.Entry<String, Object> entry : mapData.entrySet()) {
    RMBuilder.addData(entry.getKey(), entry.getValue().toString());
}

fm.send(RMBuilder.build());
}