Not getting Lat/Long on Emulator as well as on device

i am done code for getting current lat/long as follow but i always get null from lm.getLastKnownLocation(LocationManager.GPS_PROVIDER); method.

i have tried by 2 ways.

the code is below.

first way,

LocationManager lm = (LocationManager)getSystemService(Context.LOCATION_SERVICE);
Location location = lm.getLastKnownLocation(LocationManager.GPS_PROVIDER);

if(location != null)
{
    lat = location.getLatitude();
 开发者_开发问答   lon = location.getLongitude();
}

and second way,

LocationManager lm = (LocationManager)getSystemService(Context.LOCATION_SERVICE);

Log.d("GPS_PROVIDER","GPS_PROVIDER = " + lm.isProviderEnabled(LocationManager.GPS_PROVIDER));
Log.d("NW_PROVIDER","NW_PROVIDER = " + lm.isProviderEnabled(LocationManager.NETWORK_PROVIDER));

lm.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, new LocationListenerAdapter()
{
   @Override
   public void onLocationChanged(Location location) 
  {
          if(location != null)
      {
        lat = location.getLatitude();
        lon = location.getLongitude();
      }
  }
});

LocationListenerAdapter class is implements the method of LocationListener interface and i keep all method blank i.e no code written into that methods.

i also use gpx and kml file for emulator to change lat/long but i didn't get yet. can any one provide best answer.

Thanks in advance.