FCM: onNewToken vs FirebaseInstanceId

Question

Firebase has deprecated some of the messaging calls in the com.google.firebase:firebase-messaging:17.1.0 release. This post goes over those changes nicely.

Question: Can someone tell me if is it considered bad practice to not implement onNewToken and instead just call the below block each app launch This probably seems excessive to Android folks but feels like home from an iOS point of view.

FirebaseInstanceId.getInstance().instanceId.addOnSuccessListener(this) { instanceIdResult ->
    // Just use this call 
    val newToken = instanceIdResult.token
    Log.i("newToken", newToken)
}



@Override
public void onNewToken(String s) {
    super.onNewToken(s);
    // Leave this unimplemented
}

I am more familiar with iOS which calls its onNewToken equivalent on every app launch. So for iOS I put logic there to determine if my backend needs to be updated.

getInstanceId() docs say This generates an Instance ID if it does not exist yet, which starts periodically sending information to the Firebase backend. This makes me assume I can just call FirebaseInstanceId.getInstance().instanceId.addOnSuccessListener each launch.

Answer 1

Something very important that no one has mentioned yet:

If you check for the current device token only after an app launch, you might loose the event of the token being updated while your app is in the background (of course) and you won't be able to receive remote push messages from your server until the user launches the app again and you send the new token to the server.

The whole purpose of having that callback which can also be called while your app is in the background is to prevent loosing backend messages (important if your app or some important features of it relies a lot on push notifications). It is important to be aware that this callback will not only deliver you the token when you register the device for the first time but also: Called if InstanceID token is updated. This may occur if the security of the previous token had been compromised.

So:

Can someone tell me if is it considered bad practice to not implement onNewToken and instead just call the below block each app launch This probably seems excessive to Android folks but feels like home from an iOS point of view.

Yes, it is actually a bad practice to not implement onNewToken().

Answer 2

First of all, I'm highly skeptical of any logic that suggests that if something is OK in iOS, that it would be OK on Android!

The implementation of push messaging between Android and iOS is extremely different. On Android, it's dependent on Play Services, which runs in another process. On iOS, it's something completely different. The rules of engagement are simply not at all the same.

Note that the suggested token retrieval method is via callback. That is suggesting that token generation is essentially asynchronous. In other words, at app launch (in whatever way you actually define that), the background stuff that manages to token might not be done with that yet. There simply might not be any token available when you ask for it. And who knows how long that takes? You're better off just accepting the token when the system tells you it's ready instead of making a guess about when it's ready. Follow the recommended implementation path.