android - Cannot Retrieve Location's longitude an latitude -

when try run code, error:

java.lang.nullpointerexception: attempt invoke virtual method 'android.content.res.resources android.content.context.getresources()' on null object reference

i can manually configure coordinates in emulator, still, got same error.

here codes getting location coordinates.

locationtracker.java

    public class locationtracker extends mainactivity implements locationlistener {     mainactivity activity;     context context;     location location;     locationmanager lm;      double lat,longi;       boolean isgpsenabled = false;     boolean isnetworkenabled = false;     boolean cangetnetworklocation = false;      public locationtracker (context context) {         this.context=context;         getgpslocation();     }       public location getgpslocation() {          lm = (locationmanager) context.getsystemservice(context.location_service);         isgpsenabled = lm.isproviderenabled(locationmanager.gps_provider);          if (isgpsenabled) {             /** check runtime permission */            if (contextcompat.checkselfpermission(context, manifest.permission.access_fine_location) == packagemanager.permission_granted || contextcompat.checkselfpermission(context, manifest.permission.access_coarse_location) == packagemanager.permission_granted) {                 if (location == null) {      //request new data coming gps                    lm.requestlocationupdates(locationmanager.gps_provider,0,0,this);                     if (lm != null) {    //retrieve data earlier                        location=lm.getlastknownlocation(locationmanager.gps_provider);                         if (location != null) {                             lat= location.getlatitude();                             longi= location.getlongitude();                        }                    }                }               }else {                activitycompat.requestpermissions(activity,new string[]{android.manifest.permission.access_coarse_location, manifest.permission.access_fine_location},123);            }         }else {         }      return location;        }      /** latitude method */         public double getlatitude() {             if (location != null) {                 lat=location.getlatitude();             }              return lat;         }      /** longitude method */         public double getlongitude () {             if (location != null) {                 longi=location.getlongitude();             }             return longi;         }      @override     public void onlocationchanged(location location) {         lat= location.getlatitude();         longi=location.getlongitude();     }      @override     public void onstatuschanged(string provider, int status, bundle extras) {      }      @override     public void onproviderenabled(string provider) {      }      @override     public void onproviderdisabled(string provider) {      } } 

and mainactivity class displaying coordinates.

public class mainactivity extends appcompatactivity { context context; dbhelper helper; locationtracker tracker;    textview contactstv,sendemergencytv; @override protected void oncreate(bundle savedinstancestate) {     super.oncreate(savedinstancestate);     setcontentview(r.layout.activity_main);     helper=new dbhelper(getapplicationcontext());       /**      * onclick listener in android       */     contactstv=(textview) findviewbyid(r.id.tv_createcontacts);     contactstv.setonclicklistener(new view.onclicklistener() {         @override         public void onclick(view v) {             intent intent= new intent(mainactivity.this, contactsactivity.class); //redirect contacts dsadsadsa              startactivity(intent);         }     });  sendemergencytv=(textview)findviewbyid(r.id.tv_sendemergency);     sendemergencytv.setonclicklistener(new view.onclicklistener() {         @override         public void onclick(view v) {             tracker= new locationtracker(mainactivity.this);             double lat,longi;              lat= tracker.getlatitude();             longi= tracker.getlongitude();              toast.maketext(context,"latitude: "+lat+ "longitude: "+longi,toast.length_long).show();         }     }); }  } 

by way, not sure of placing mainactivity instance inside locationtracker class in requestpermission parameter.

here:

activitycompat.requestpermissions(activity,            new string[]{android.manifest.permission.access_coarse_location,                        manifest.permission.access_fine_location},123); 

line causing issue because activity null.

use ((activity)context) instead of activity.like:

activitycompat.requestpermissions(((activity)context),            new string[]{android.manifest.permission.access_coarse_location,                        manifest.permission.access_fine_location},123); 

note:

also, because locationtracker normal java class no need extends activity in it.