LocationListener InSide AsyncTask

Question

您好，我是 Android 编程新手，目前正在开发一个应用程序，该应用程序使用位置管理器来获取用户位置并在地图上放置标记。我正在尝试使用 AsyncTask 来运行 LocationListener 并在用户位置更改时不断更新标记。 这是我正在上的课...

public class IncidentActivity extends MapActivity{


   public void onCreate(Bundle savedInstanceState){
       super.onCreate(savedInstanceState);
       this.setContentView(R.layout.incidentactivity);

       mapView = (MapView)findViewById(R.id.mapView);
       mapView.setBuiltInZoomControls(true);   
       mapView.setTraffic(true);


        mapController = mapView.getController();
        String coordinates[] = {"-26.167004","27.965505"};
        double lat = Double.parseDouble(coordinates[0]);
        double lng = Double.parseDouble(coordinates[1]);
        geoPoint = new GeoPoint((int)(lat*1E6), (int)(lng*1E6));
        mapController.animateTo(geoPoint);
        mapController.setZoom(16);
        mapView.invalidate();

         new MyLocationAsyncTask().execute();

   }



      private class MyLocationAsyncTask extends AsyncTask<Void, Location, Void> implements LocationListener{
        private  double latLocation;
        private Location l;

        //location management variables to track and maintain user location
        protected LocationManager locationManager;
        protected LocationListener locationListener;

        @Override
        protected Void doInBackground(Void... arg0) {
            Looper.prepare();
              locationManager = (LocationManager)getSystemService(Context.LOCATION_SERVICE);
              locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 1, locationListener);

              this.publishProgress(l);
            return null;
        }

        @Override
        protected void onPostExecute(Void result) {

            super.onPostExecute(result);
        }

        @Override
        protected void onProgressUpdate(Location... values) {

            super.onProgressUpdate(values);
        }

        //this method is never executed i dont know why...?
        public void onLocationChanged(Location location) {
            if (location != null){
                latLocation = location.getLatitude(); 
                Toast.makeText(getBaseContext(), " Your latLocation :" + latLocation, Toast.LENGTH_LONG).show();
                //Log.d("Your Location", ""+latLocation);
            }
        }

        public void onProviderDisabled(String provider) {


        }

        public void onProviderEnabled(String provider) {
            // TODO Auto-generated method stub

        }

        public void onStatusChanged(String provider, int status, Bundle extras) {
            // TODO Auto-generated method stub

        }


      }


}

Answer 1

我刚刚实现了这样的AsyncTask：

class GetPositionTask extends AsyncTask<Void, Void, Location> implements LocationListener
{
    final long TWO_MINUTES = 2*60*1000;
    private Location location;
    private LocationManager lm;

    protected void onPreExecute()
    {
        // Configure location manager - I'm using just the network provider in this example
        lm = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
        lm.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 1000, 0, this);
        nearProgress.setVisibility(View.VISIBLE);
    }

    protected Location doInBackground(Void... params)
    {
        // Try to use the last known position
        Location lastLocation = lm.getLastKnownLocation(LocationManager.NETWORK_PROVIDER);

        // If it's too old, get a new one by location manager
        if (System.currentTimeMillis() - lastLocation.getTime() > TWO_MINUTES)
        {
            while (location == null)
                try { Thread.sleep(100); } catch (Exception ex) {}

            return location;
        }

        return lastLocation;
    }

    protected void onPostExecute(Location location)
    {
        nearProgress.setVisibility(View.GONE);
        lm = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
        lm.removeUpdates(this);

        // HERE USE THE LOCATION
    }

    @Override
    public void onLocationChanged(Location newLocation)
    {
        location = newLocation;
    }

    public void onProviderDisabled(String provider) {}
    public void onProviderEnabled(String provider) {}
    public void onStatusChanged(String provider, int status, Bundle extras) {}
}

Answer 2

根据我的阅读和尝试，您不能在 ASyncTask 内使用循环器（位置侦听器需要它）。 点击此处

实际上这意味着两个线程模型不兼容，所以你不能
一起使用这些。 Looper 希望拥有您关联的线程
它与，而 AsyncTask 拥有它为您创建的线程，以便在
背景。因此它们相互冲突，不能一起使用。

Dianne Hackborn 建议使用 HandlerThread，但我成功地让我的线程在 IntentService 内部工作。我承认我的代码仍然有点hack。