Preventing FCM Token Failures from Crashing an Android App

After integrating Firebase Cloud Messaging, the app sometimes crashed during its first two minutes. The log showed:

Fetching FCM registration token failed
java.io.IOException: java.util.concurrent.ExecutionException: java.io.IOException: SERVICE_NOT_AVAILABLE

First verify Google Play Services availability:

public static boolean supportsGoogleServices(Context context) {
    GoogleApiAvailability api = GoogleApiAvailability.getInstance();
    return api.isGooglePlayServicesAvailable(context) == ConnectionResult.SUCCESS;
}

Dependency:

implementation 'com.google.android.gms:play-services-base:18.5.0'

The service may also be unavailable because of the device’s network environment. More importantly, do not call task.getResult() after a failed task. Return immediately or handle the exception:

FirebaseMessaging.getInstance().getToken().addOnCompleteListener(task -> {
    if (!task.isSuccessful()) {
        Log.w(TAG, "Fetching FCM registration token failed", task.getException());
        myFCMtoken = null;
        return;
    }

    myFCMtoken = task.getResult();
    Log.d(TAG, "FCM Token: " + myFCMtoken);
});

After guarding the failed result and uninitialized token, the crashes stopped.