Why I have to pre-set the collection and document name in GeoFireStore to setlocation

Question

I want to setLocation automatically from my app without presetting collection and document name.

public class MainActivity extends AppCompatActivity {
    CollectionReference ref = FirebaseFirestore.getInstance().collection("collection");
    GeoFire geoFire = new GeoFire(ref);

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        geoFire.setLocation("firebase-hq", new GeoLocation(26.48956, 94.89945));