Why GPS tracker extends Service

Question

For using the android location based services we use the GPS tracker class which extends Service and implements LocationListener interface. What is the use of Service class here ? Is it only for getting the location updates in the background or something more ?

Example code below :

public class GPSTracker extends Service implements LocationListener {

   private final Context mContext;

   // 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 GPSTracker(Context context) {
      this.mContext = context;
      getLocation();
   }

   public Location getLocation() {
      try {
         locationManager = (LocationManager) mContext.getSystemService(LOCATION_SERVICE);

         // getting GPS status
         isGPSEnabled = locationManager.isProviderEnabled(LocationManager.GPS_PROVIDER);

         // getting network status
         isNetworkEnabled = locationManager
            .isProviderEnabled(LocationManager.NETWORK_PROVIDER);

         if (!isGPSEnabled && !isNetworkEnabled) {
            // no network provider is enabled
         } else {
            this.canGetLocation = true;
            // First get location from Network Provider
            if (isNetworkEnabled) {
               locationManager.requestLocationUpdates(
                  LocationManager.NETWORK_PROVIDER,
                  MIN_TIME_BW_UPDATES,
                  MIN_DISTANCE_CHANGE_FOR_UPDATES, this);

               Log.d("Network", "Network");
               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,
                     MIN_DISTANCE_CHANGE_FOR_UPDATES, this);

                  Log.d("GPS Enabled", "GPS Enabled");
                  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(GPSTracker.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;
   }

   /**
      * 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 is settings");

      // Setting Dialog Message
      alertDialog.setMessage("GPS is not enabled. Do you want to go to settings menu?");

      // On pressing Settings button
      alertDialog.setPositiveButton("Settings", 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 arg0) {
      return null;
   }
}

Answer 1

The main purpose of that is not to be activity lifecycle dependent. Most possibly you do not want to destroy and create a new GpsTracker each time user navigates between activities.

Thus, Services come into the stage.

Nevertheless, you should strongly consider to evade from such technique in favour of FusedLocationProviderApi, which aims to optimize battery usage.