Basically "whats's here" return address detail related to that particular latitude and longitude. So for that you can use below code and yes it good to be add result to InfoWindowAdapter
Geocoder geocoder;
List<Address> addresses;
geocoder = new Geocoder(this, Locale.getDefault());
addresses = geocoder.getFromLocation(latitude, longitude, 1);
String address = addresses.get(0).getAddressLine(0);
String city = addresses.get(0).getAddressLine(1);
String country = addresses.get(0).getAddressLine(2);