when map is ready, in my MapsActivity.java, it do not show anything but just google logo and zoom control arrows.
public void onMapReady(GoogleMap googleMap) {
    mMap = googleMap;
    LatLng sydney = new LatLng(41.4538381,15.5532994);
    mMap.addMarker(new MarkerOptions().position(sydney).title("Marker in Sydney"));
    mMap.moveCamera(CameraUpdateFactory.newLatLng(sydney));
    UiSettings mapSettings = mMap.getUiSettings();
    mapSettings.setZoomControlsEnabled(true);
}