Android: Firebase token is null at first run

Question

I am using FCM to provide notifications in my app. Everything worked well, but now I realised that, when I install my application using Android Studio (not from GooglePlay) the token is null at first run. When I close my app and restart it, the token is not null anymore. What cause this problem and how can I avoid it?

InstanceIDService:

public class InstanceIDService extends FirebaseInstanceIdService {      @Override     public void onTokenRefresh() {          String token = FirebaseInstanceId.getInstance().getToken();         registerToken(token);     }      private void registerToken(String token) {          OkHttpClient client = new OkHttpClient();         RequestBody body = new FormBody.Builder()                 .add("Token",token)                 .build();          Request request = new Request.Builder()                 .url("url_to_registration_script")                 .post(body)                 .build();          try {             client.newCall(request).execute();         } catch (IOException e) {             e.printStackTrace();         }     } } 

In MainActivity:

FirebaseMessaging.getInstance().subscribeToTopic("topic"); String token = FirebaseInstanceId.getInstance().getToken(); Log.d("TOKEN", token); 

Last log returns null when app is installed and started for the first time

Registration script:

 <?php   if (isset($_POST["Token"])) {         $_uv_Token=$_POST["Token"];        $conn = mysqli_connect("localhost","user","pass","db") or die("Error connecting");        $q="INSERT INTO users (Token) VALUES ( '$_uv_Token') "           ." ON DUPLICATE KEY UPDATE Token = '$_uv_Token';";    mysqli_query($conn,$q) or die(mysqli_error($conn));   mysqli_close($conn); } ?> 

Answer 1

The token is fetched asynchronously on first app start. You have to wait for onTokenRefresh() to be called in your FirebaseInstanceIdService before the token can be accessed.

Answer 2

uninstall the app from emulator and run again , so that the onTokenRefreshed method will be called again .

To check wether you are already registered and you just want to know the FCM TOken

String refreshedToken = FirebaseInstanceId.getInstance().getToken(); 

add the above line in MyFirebaseMessagingService class any where(in oncreate method ) and just Toast or log the refreshedToken.