爲什麼GPS追蹤器擴展服務

Question

對於使用基於android位置的服務，我們使用擴展了Service並實現LocationListener接口的GPS追蹤器類。這裏有什麼服務類的用法？它只是爲了獲得位置更新在後臺或更多？

實施例以下代碼：

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

的該主要目的是不被活動的生命週期相關的。每當用戶在活動之間導航時，大多數情況下您都不想銷燬並創建新的GpsTracker。因此，Services進入階段。然而，你應該強烈考慮避開這種技術，轉而採用FusedLocationProviderApi，其目標是優化電池的使用。