Android : How does onLocationChanged works?

in my application i have a button that start counting the time how long the user has been in the same location. and i want the app stop the timer counting if the user goes out from the area he started so i made a class that give me the current location (LAT,LONG,PLACE NAME) and i don't know how to use the "onLocationChanged" and Should I use it? or something else for what i need?

public class MapCurrentPlace extends Service implements LocationListener {


    private final Context mContext;

    public static final String MY_TEMP = "sharedFile"; 

    SharedPreferences setting;
    SharedPreferences.Editor editor;


    // 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
    String placeName = "";


    // The minimum distance to change Updates in meters
    private static final long MIN_DISTANCE_CHANGE_FOR_UPDATES = 0; // 10 meters

    // The minimum time between updates in milliseconds
    private static final long MIN_TIME_BW_UPDATES = 500; // 1 minute

    // Declaring a Location Manager
    protected LocationManager locationManager;



    public MapCurrentPlace(Context context) {
        this.mContext = context;
        getLocation();

    }



    public String getPlaceName(){

            Geocoder gc = new Geocoder(mContext);
        try {
                List<Address>  list = gc.getFromLocation(latitude, longitude, 1);
                 if(list.size()>0){
                String city = list.get(0).getLocality();
                String street = list.get(0).getAddressLine(0);
                placeName = city+", "+street+"";        
    }
            } catch (IOException e) {
            placeName = "";         
            e.printStackTrace();
            }



        return placeName;
    }


    public Location getLocation() {

        try {
            locationManager = (LocationManager) mContext
                    .getSystemService(Context.LOCATION_SERVICE);
                        // getting network status
            isNetworkEnabled = locationManager
                    .isProviderEnabled(LocationManager.NETWORK_PROVIDER);
                      // getting GPS status
            isGPSEnabled = locationManager
                    .isProviderEnabled(LocationManager.GPS_PROVIDER);








            if (!isGPSEnabled) {
                // no network provider is enabled

                 this.canGetLocation = false;
                return null;

            } else {
                this.canGetLocation = true;
                if (isNetworkEnabled) {

                    locationManager.requestLocationUpdates( LocationManager.NETWORK_PROVIDER,MIN_TIME_BW_UPDATES,0, this);

                    if (locationManager != null) {
                        location = locationManager.getLastKnownLocation(LocationManager.NETWORK_PROVIDER);

                        if (location != null) {
                            latitude = location.getLatitude();
                            longitude = location.getLongitude();
                        }

                    }
                }
                // if GPS Enabled get lat/long using GPS Services
                if (isGPSEnabled) {
                    if (location == null) {
                        locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER,MIN_TIME_BW_UPDATES,0, this);

                        if (locationManager != null) {
                            location = locationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER);
                                if (location != null) {
                                    latitude = location.getLatitude();
                                    longitude = location.getLongitude();

                            }
                        }
                    }
                }
            }

        } catch (Exception e) {
            e.printStackTrace();

        }
        return location;
    }


    /**
     * Stop using GPS listener
     * Calling this function will stop using GPS in your app
     * */
    public void stopUsingGPS(){
        if(locationManager != null){
            locationManager.removeUpdates(MapCurrentPlace.this);
        }     
    }

    /**
     * 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;
    }

    public boolean getIsNetworkEnabled() {

        return this.isNetworkEnabled;
    }

    /**
     * Function to show settings alert dialog
     * On pressing Settings button will lauch Settings Options
     * */
    public void showSettingsAlert(){
        AlertDialog.Builder alertDialog = new AlertDialog.Builder(mContext);

        // Setting Dialog Title
        alertDialog.setTitle("GPS OFF");

        // Setting Dialog Message
        alertDialog.setMessage("Allow GPS");

        // On pressing Settings button
        alertDialog.setPositiveButton("SETTING", new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog,int which) {
                Intent intent = new Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS);
                mContext.startActivity(intent);
            }
        });

        // on pressing cancel button
        alertDialog.setNegativeButton("CANCEL", new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog, int which) {
            dialog.cancel();
            }
        });

        // Showing Alert Message
        alertDialog.show();
    }

    @Override
    public void onLocationChanged(Location location) {

    }

    @Override
    public void onProviderDisabled(String provider) {
    }

    @Override
    public void onProviderEnabled(String provider) {
    }

    @Override
    public void onStatusChanged(String provider, int status, Bundle extras) {
    }


    @Override
    public IBinder onBind(Intent intent) {
        // TODO Auto-generated method stub
        return null;
    }



}