Loading KML file onto Google Map

Question

I tried implementing KML in Google Maps fragment following official documentation (https://developers.google.com/maps/documentation/android-sdk/utility/kml) but it didn't work. There are no errors, map opens but no KML overlay. I know how to load KML from a local file (stored in raw folder), but I'm trying to do the same through URL leading to KML file (stored on GitHub Gist).

Here's the code:

public void onMapReady(GoogleMap googleMap) {
    mMap = googleMap;
    try {
        InputStream inputStream = new URL("https://gist.githubusercontent.com/...route.kml").openStream();
        KmlLayer layer = new KmlLayer(mMap, inputStream, getApplicationContext());
        layer.addLayerToMap();
    } catch (Exception e) {
        e.printStackTrace();
    }
}