How to access SharedPreference within Service in Android - service

Question

I am working on a service that will capture longitude and latitude implementing LocationListener.
Also I am trying to update the longitude and latitude values in sharedpreference as they get captured.
However I am getting runtime error while using sharedpreference within service. I think the problem is with context. I have tried, getApplicationContext(), getBaseContext() but not working.
public class GPSTracker extends Service implements LocationListener {
private final Context mContext;
// private GPSTrackerImplementation mCallback;
// flag for GPS status
boolean isGPSEnabled = false;
// flag for network status
boolean isNetworkEnabled = false;
// flag for GPS status
boolean canGetLocation = false;
Location location; // location
double latitude; // latitude
double longitude; // longitude
// The minimum distance to change Updates in meters
private static final long MIN_DISTANCE_CHANGE_FOR_UPDATES = 10; // 10 meters
// The minimum time between updates in milliseconds
private static final long MIN_TIME_BW_UPDATES = 1000 * 60 * 1; // 1 minute
// Declaring a Location Manager
protected LocationManager locationManager;
//public SharedPrefference shareObj;
String address;
String city;
String state;
String country;
String postalCode;
String knownName;
Geocoder geocoder;
List<Address> addresses;
public SharedPrefference shareObj;
public GPSTracker(Context context) {
this.mContext = context;
// PreferenceManager.getDefaultSharedPreferences(context);
// SharedPreferences preferences = PreferenceManager.getDefaultSharedPreferences(this);
try {
locationManager = (LocationManager) mContext.getSystemService(LOCATION_SERVICE);
// getting network status
isNetworkEnabled = locationManager.isProviderEnabled(LocationManager.NETWORK_PROVIDER);
// getting GPS status
isGPSEnabled = locationManager.isProviderEnabled(LocationManager.GPS_PROVIDER);
if (!isGPSEnabled && !isNetworkEnabled) {
//PreferenceManager.getDefaultSharedPreferences(context).edit().putString("GPS_ENABLED", "Y").commit();
// if (!isGPSEnabled) {
// no network provider is enabled
} else this.canGetLocation = true;
// First get location from Network Provider
if (isNetworkEnabled) {
locationManager = (LocationManager) mContext.getSystemService(LOCATION_SERVICE);
locationManager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, MIN_TIME_BW_UPDATES, MIN_DISTANCE_CHANGE_FOR_UPDATES, this);
Log.d("Network", "Network");
getLocation();
}
if (isGPSEnabled) {
if (location == null) {
locationManager = (LocationManager) mContext.getSystemService(LOCATION_SERVICE);
locationManager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, MIN_TIME_BW_UPDATES, MIN_DISTANCE_CHANGE_FOR_UPDATES, this);
Log.d("GPS", "GPS");
getLocation();
}
}
}catch (SecurityException e) {
e.printStackTrace();
}
getLocation();
}
public Location getLocation() {
try {
if (locationManager != null) {
location = locationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER);
//location = locationManager.getLastKnownLocation(LocationManager.NETWORK_PROVIDER);
if (location != null) {
latitude = location.getLatitude();
longitude = location.getLongitude();
Log.d("On constructor-GPS", "latitude"+latitude);
Log.d("On constructor-GPS", "longitude"+longitude);
return location;
}
else {
return locationManager.getLastKnownLocation(LocationManager.NETWORK_PROVIDER);
}
}
}catch (SecurityException e) {
e.printStackTrace();
}
return location;
}
/**
* Function to get latitude
*/
public double getLatitude() {
if (location != null) {
latitude = location.getLatitude();
}
// return latitude
return latitude;
}
/**
* Function to get longitude
*/
public double getLongitude() {
if (location != null) {
longitude = location.getLongitude();
}
// return longitude
return longitude;
}
/**
* Function to check GPS/wifi enabled
*
* #return boolean
*/
public boolean canGetLocation() {
return this.canGetLocation;
}
/**
* Function to show settings alert dialog
* On pressing Settings button will lauch Settings Options
*/
#Override
public void onLocationChanged(Location location) {
this.location = location;
latitude = location.getLatitude();
longitude = location.getLongitude();
// Toast.makeText(this, "location changed", Toast.LENGTH_LONG).show();
Log.d("n location changed", "latitude"+latitude);
Log.d("On location changed", "longitude"+longitude);
String m_latStr = Double.toString(latitude);
String m_longStr = Double.toString(longitude);
PreferenceManager.getDefaultSharedPreferences(getBaseContext()).edit().putString("LATITUDE", m_latStr).commit();
PreferenceManager.getDefaultSharedPreferences(getBaseContext()).edit().putString("LONGITUDE", m_longStr).commit();
}
LOGCAT
java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.content.Context.getPackageName()' on a null object reference
at android.preference.PreferenceManager.getDefaultSharedPreferencesName(PreferenceManager.java:375)
at android.preference.PreferenceManager.getDefaultSharedPreferences(PreferenceManager.java:370)
at com.teamlease.gps.services.GPSTracker.onLocationChanged(GPSTracker.java:195)
at android.location.LocationManager$ListenerTransport._handleMessage(LocationManager.java:285)
at android.location.LocationManager$ListenerTransport.-wrap0(LocationManager.java)
at android.location.LocationManager$ListenerTransport$1.handleMessage(LocationManager.java:230)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5443)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:728)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618)