Android GPS跟踪器为何扩展服务

为了使用android基于位置的服务，我们使用GPS tracker类，该类扩展了服务并实现了LocationListener接口。服务类在这里有什么用？它只是为了在后台获取位置更新还是其他什么

示例代码如下：

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;
   }
}

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其主要目的不是依赖于活动生命周期。很可能您不希望每次用户在活动之间导航时销毁并创建新的

GpsTracker

因此，

服务

进入了这个阶段

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但是，你应该强烈地考虑避开这种技术，这是为了优化电池的使用。< / P>不要使用它。这是坏代码。有。因为这很糟糕，androidhive的所谓教程。谢谢@azizbekian。您能详细说明一下吗？对不起，您能重新表述一下您的意思吗？当然不，真正的服务需要没有参数的构造函数，它不需要上下文作为上下文，显然不能用新操作符“启动”而不提您不能从服务以这种方式启动对话框。。。这只是可怕的androidhive网站上的一个例子。