Firebase push notification on new chat message

I have created an app where I have chat in it.

I would like that the users will receive a notification that they got a new message whenever they are outside of the app.

In order to do so, I'm using Firebase service.

Now, whenever a message is sent, I call this method:
I have created the following MyFirebaseMessagingService class to test when it is called:

private class MyTask extends AsyncTask<MyTaskParams, Void, Void> {
    @Override
    protected Void doInBackground(MyTaskParams... params) {
        String userDeviceIdKey = params[0].url;
        String title = params[0].title;
        String body = params[0].body;

        String authKey = "XXXXX";   // You FCM AUTH key
        String FMCurl = "https://fcm.googleapis.com/fcm/send";
        URL url;
        try {
            url = new URL(FMCurl);
            HttpURLConnection conn = (HttpURLConnection) url.openConnection();

            conn.setUseCaches(false);
            conn.setDoInput(true);
            conn.setDoOutput(true);

            conn.setRequestMethod("POST");
            conn.setRequestProperty("Authorization","key="+authKey);
            conn.setRequestProperty("Content-Type","application/json");

            JSONObject json = new JSONObject();
            json.put("to",userDeviceIdKey);
            json.put("priority","high");
            JSONObject info = new JSONObject();
            info.put("title", title);   // Notification title
            info.put("body", body); // Notification body
            info.put("var1", chatID);
            info.put("var2",receiverID);
            info.put("var3",itemID);
            json.put("data", info);

            OutputStreamWriter wr = new OutputStreamWriter(conn.getOutputStream());
            wr.write(json.toString());
            wr.flush();
            Log.w("", "getInstanceId failed" + json);

            conn.getInputStream();

        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } catch (JSONException e) {
            e.printStackTrace();
        }

        return null;
    }
}

and In my Service I created:

public class MyFirebaseMessagingService extends FirebaseMessagingService {

    @Override
    public void onMessageReceived(RemoteMessage remoteMessage) {

        Log.d("TESTING_MESSAGE", "" + remoteMessage);

    }

}

However, It seems like I never get this Log when I send a message and it doesnt look like onMessageReceived is ever called.

Is there any reason?

My next goal is to make notification inside onMessageReceived but I want to make sure first that I get there.

My manifest is:

<service
    android:name=".service.MyFirebaseMessagingService"
    android:permission="com.google.android.c2dm.permission.SEND">
    <intent-filter>
        <action android:name="com.google.firebase.MESSAGING_EVENT" />
        <action android:name="com.google.android.c2dm.intent.RECEIVE" />
    </intent-filter>
</service>

I make a demo app with your code, and it works well and I can see that onMessageReceived function is trigged when a message arrives.

I use the firebase-messaging version 20.1.7

implementation 'com.google.firebase:firebase-messaging:20.1.7'

so I think you should do the following checking:

1. check if your app is in the foreground. because you can't trigger onMessageReceived when the app is in the background. refer: https://firebase.google.com/docs/cloud-messaging/android/receive#handling_messages

2. check if you wrote the right device token(your field 'userDeviceIdKey') when you sent the http request.

3. check if your http request has some error in catch.

hope can help you.

The onMessageReceived() method will never be called if the app is killed.
https://stackoverflow.com/questions/37358462/firebase-onmessagereceived-not-called-when-app-in-background

First of all check what you send: data message or notification message.
They may look the same, but depending on what type of message, the different method called.
Check this out: https://firebase.google.com/support/faq/#fcm-android-background

// Check if message contains a notification payload.

if (remoteMessage.getNotification() != null) {
  Map test = remoteMessage.getData();
  Log.d(TAG, "Message data payload: " + test);

// Check if message contains a data payload.

 if (remoteMessage.getData().size() > 0) {
    if (remoteMessage.getNotification() != null) {
            Log.d(TAG, "Message Notification Body: " + 
           remoteMessage.getNotification().getBody());