google maps - Get latitude and longitude for Android App (getLastKnownLocation is null) -

i latitude , longitude current location in app. testing on galaxy wi-fi 5.0. need numbers in double format gonna use in google-maps-url. problem lm.getlastknownlocation(locationmanager.gps_provider) returns null , nullpointerexception.

private void getlatitudelongitude() {         locationmanager lm = (locationmanager)getsystemservice(context.location_service);          location location = lm.getlastknownlocation(locationmanager.gps_provider);          if(location != null) {             showmyaddress(location);         }          final locationlistener locationlistener = new locationlistener() {             public void onlocationchanged(location location) {                 showmyaddress(location);             }              public void onproviderdisabled(string arg0) {                 // todo auto-generated method stub              }              public void onproviderenabled(string arg0) {                 // todo auto-generated method stub              }              public void onstatuschanged(string arg0, int arg1, bundle arg2) {                 // todo auto-generated method stub              }         };          lm.requestlocationupdates(locationmanager.gps_provider, 2000, 10, locationlistener);           geocoder mylocation = new geocoder(getapplicationcontext(), locale.getdefault());            try {             system.out.println(mylocation.getfromlocation(latitude, longitude, 1).tostring());         } catch (ioexception e) {             // todo auto-generated catch block             e.printstacktrace();         } }  private void showmyaddress(location location) {     double latitude = location.getlatitude();     double longitude = location.getlongitude();     geocoder mylocation = new geocoder(getapplicationcontext(), locale.getdefault());        try {         system.out.println( mylocation.getfromlocation(latitude, longitude, 1).tostring());      } catch (ioexception e1) {         // todo auto-generated catch block         e1.printstacktrace();     } }