Firebase FCM token - When to send to server?

Question

Okay so I have an app which on first start takes you through a few welcoming slides, then takes you to a login/register page and then to MainActivity.

I

Answer 1

Yes FCM token is generated automatically. But try to see this in a different angle.

This is how I handled it.

Let FCM generate token as soon as your app starts. OnTokenRefresh will be called and you just save it in your preferences as:

@Override
public void onTokenRefresh() {
    // Get updated InstanceID token.
    String refreshedToken = FirebaseInstanceId.getInstance().getToken();
    Log.d(TAG, "Refreshed token: " + refreshedToken);

    sendRegistrationToServer(refreshedToken);
}

private void sendRegistrationToServer(String token) {
    // Add custom implementation, as needed.
    SharedPreferenceUtils.getInstance(this).setValue(getString(R.string.firebase_cloud_messaging_token), token);
    
   // To implement: Only if user is registered, i.e. UserId is available in preference, update token on server.
   int userId = SharedPreferenceUtils.getInstance(this).getIntValue(getString(R.string.user_id), 0);
   if(userId != 0){
       // Implement code to update registration token to server
   }
}

Hope you are clear with the way. Ask if you need more clearance on it.

Edit

Using the new Firebase SDK (21.0.0) , you need to override onNewToken() method instead of onTokenRefresh()

 @Override
public void onNewToken(@NonNull String s) {
    super.onNewToken(s);
    sendRegistrationToServer(s);
}