public void OnMapReady (GoogleMap googleMap) { googleMap.MoveCamera (CameraUpdateFactory.NewLatLngZoom (NEWARK, 11)); images.Clear (); images.Add (BitmapDescriptorFactory.FromResource (Resource.Drawable.newark_nj_1922)); images.Add (BitmapDescriptorFactory.FromResource (Resource.Drawable.newark_prudential_sunny)); currentEntry = 0; groundOverlay = googleMap.AddGroundOverlay (new GroundOverlayOptions () .InvokeImage (images [currentEntry]) .Anchor (0, 1) .Position (NEWARK, 8600f, 6500f)); transparencyBar.ProgressChanged += (sender, e) => { if (groundOverlay != null) groundOverlay.Transparency = (float)e.Progress / (float)TRANSPARENCY_MAX; }; googleMap.SetContentDescription ("Google Map with ground overlay."); }