Location Services

In method onMarkerSelect I have selected marker. How can I get corresponding Placemark or its key?

If you are using the latest version of the SDK (4.0) you can simply get the placemark with getMapView().getAssociatedPlacemark(marker); Otherwise, you can do something like: 

Placemark p = null;
if(marker instanceof PlacemarkMarker)
    p = ((PlacemarkMarker) marker).getPlacemark();
if(p!=null){
    // Do something.
}