android - Why I can't get my position? -

i'm making app android studio , in welcome popup dialog want app gets users's position i've written code, why can't find position. why?!?i'm trying days make work. here's code

public class mainactivity extends activity implements locationlistener { private textview latitutefield; private textview longitudefield; private textview addressfield;  private locationmanager locationmanager; private string provider;   @override public void oncreate(bundle savedinstancestate) {     super.oncreate(savedinstancestate);     setcontentview(r.layout.activity_main);     latitutefield = (textview) findviewbyid(r.id.textview02);     longitudefield = (textview) findviewbyid(r.id.textview04);     addressfield = (textview) findviewbyid(r.id.textview05);       locationmanager = (locationmanager) getsystemservice(context.location_service);      criteria criteria = new criteria();     provider = locationmanager.getbestprovider(criteria, true);     log.d("sometag", provider);     log.d("sometag", string.valueof(locationmanager.isproviderenabled(provider)));     location location = locationmanager.getlastknownlocation(provider);       if (location != null) {         system.out.println("provider " + provider + " has been selected.");         onlocationchanged(location);     } else {         latitutefield.settext("please wait location update...");         longitudefield.settext("please wait location update...");         addressfield.settext("please wait location update...");     } }   @override protected void onresume() {     super.onresume();     locationmanager.requestlocationupdates(provider, 400, 1, this); }   @override protected void onpause() {     super.onpause();     locationmanager.removeupdates(this); }  @override public void onlocationchanged(location location) {      double lat = location.getlatitude();     double lng = location.getlongitude();      geocoder geocoder = new geocoder(this, locale.getdefault());     stringbuilder builder = new stringbuilder();     try {         list<address> address = geocoder.getfromlocation(lat, lng, 1);         int maxlines = address.get(0).getmaxaddresslineindex();         (int i=0; i<maxlines; i++) {             string addressstr = address.get(0).getaddressline(i);             builder.append(addressstr);             builder.append(" ");         }          string fnialaddress = builder.tostring();           latitutefield.settext(string.valueof(lat));         longitudefield.settext(string.valueof(lng));         addressfield.settext(fnialaddress);       } catch (ioexception e) {}     catch (nullpointerexception e) {} }  @override public void onstatuschanged(string provider, int status, bundle extras) {   }  @override public void onproviderenabled(string provider) {     toast.maketext(this, "enabled new provider " + provider,             toast.length_short).show();  }  @override public void onproviderdisabled(string provider) {     toast.maketext(this, "disabled provider " + provider,             toast.length_short).show(); } } 

can me find what's wrong? if more simple, need app know place (i mean city) live

read android documentation location strategies here. need add listener location updates. getlastknownlocation() should still work though, can not rely on it. also, testing on emulator? there null result, if have not set location dev tools.