Android 位置管理器不起作用

Question

我正在尝试创建和显示设备当前位置和定义点之间的路线。我使用这段代码:

public class RoutePath extends MapActivity {
    /** Called when the activity is first created. */
    MapView mapView;
    private RoutePath _activity;
    GeoPoint srcGeoPoint,destGeoPoint;
    private static List<Overlay> mOverlays;
    MapController mc;
    Location location;
    private MyLocationOverlay myLocationOverlay;
    String n;
    double longitude;
    double latitude;


    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        SharedData data = SharedData.getInstance();
        mapView = new MapView(this,"apyKey");
        mapView.setClickable(true); 




        setContentView(mapView);
        _activity = this;
        LocationManager lm = (LocationManager)getSystemService(Context.LOCATION_SERVICE); 
        Location location =lm.getLastKnownLocation(LocationManager.NETWORK_PROVIDER);
        longitude = location.getLongitude();
        latitude = location.getLatitude();

        double src_lat = latitude;
        double src_long = longitude;
        double dest_lat = 38.1267303;
        double dest_long = 13.3466097;

       String n = String.valueOf(src_long);
       Log.d("asd",n);

        if(src_lat == -1 || src_long == -1 || dest_lat == -1 || dest_long == -1){
            showAlert("Please enter source and destination points");
        }else{

            srcGeoPoint = new GeoPoint((int) (src_lat * 1E6),(int) (src_long * 1E6));
            destGeoPoint = new GeoPoint((int) (dest_lat * 1E6),(int) (dest_long * 1E6));

            List<Overlay> mapOverlays = mapView.getOverlays();
            Drawable srcdrawable = this.getResources().getDrawable(R.drawable.pushpin1);
            CustomItemizedOverlay srcitemizedOverlay = new CustomItemizedOverlay(srcdrawable);
            //CustomItemizedOverlay srcitemizedOverlay = new CustomItemizedOverlay(getDrawable("com/agarwal/route/pin_green.png"));
            OverlayItem srcoverlayitem = new OverlayItem(srcGeoPoint, "Hello!", "This is your Location.");

            Drawable destdrawable = this.getResources().getDrawable(R.drawable.pushpin1);
            CustomItemizedOverlay  destitemizedOverlay = new CustomItemizedOverlay( destdrawable );
           // CustomItemizedOverlay destitemizedOverlay = new CustomItemizedOverlay(getDrawable("com/agarwal/route/pin_red.png"));
            OverlayItem destoverlayitem = new OverlayItem(destGeoPoint, "Hello!", "This is dest Location.");

            srcitemizedOverlay.addOverlay(srcoverlayitem);
            destitemizedOverlay.addOverlay(destoverlayitem);

            mapOverlays.add(srcitemizedOverlay);
            mapOverlays.add(destitemizedOverlay);

            connectAsyncTask _connectAsyncTask = new connectAsyncTask();
            _connectAsyncTask.execute();       
            mapView.setBuiltInZoomControls(true);
            mapView.displayZoomControls(true);
            mOverlays = mapView.getOverlays();
            mapView.getController().animateTo(srcGeoPoint);
            mapView.getController().setZoom(12);
        }
    }
    @Override
    protected boolean isRouteDisplayed() {
        // TODO Auto-generated method stub
        return false;
    }
    //era private prima di 
   private class connectAsyncTask extends AsyncTask<Void, Void, Void>{
        private ProgressDialog progressDialog;
        @Override
        protected void onPreExecute() {
            // TODO Auto-generated method stub
            super.onPreExecute();

            progressDialog = new ProgressDialog(_activity);
            progressDialog.setMessage("Caricamento del percorso...");
            progressDialog.setIndeterminate(true);
            progressDialog.show();
        }
        @Override
        protected Void doInBackground(Void... params) {
            // TODO Auto-generated method stub
            fetchData();

            return null;
        }
        @Override
        protected void onPostExecute(Void result) {
            // TODO Auto-generated method stub
            super.onPostExecute(result);           
            if(doc!=null){
                Overlay ol = new MyOverlay(_activity,srcGeoPoint,srcGeoPoint,1);
                mOverlays.add(ol);
                NodeList _nodelist = doc.getElementsByTagName("status");
                Node node1 = _nodelist.item(0);
                String _status1  = node1.getChildNodes().item(0).getNodeValue();
                if(_status1.equalsIgnoreCase("OK")){
                    NodeList _nodelist_path = doc.getElementsByTagName("overview_polyline");
                    Node node_path = _nodelist_path.item(0);
                    Element _status_path = (Element)node_path;
                    NodeList _nodelist_destination_path = _status_path.getElementsByTagName("points");
                    Node _nodelist_dest = _nodelist_destination_path.item(0);
                    String _path  = _nodelist_dest.getChildNodes().item(0).getNodeValue();
                    List<GeoPoint> _geopoints = decodePoly(_path);
                    GeoPoint gp1;
                    GeoPoint gp2;
                    gp2 = _geopoints.get(0);
                    Log.d("_geopoints","::"+_geopoints.size());
                    for(int i=1;i<_geopoints.size();i++) // the last one would be crash
                    {

                        gp1 = gp2;
                        gp2 = _geopoints.get(i);
                        Overlay ol1 = new MyOverlay(gp1,gp2,2,Color.BLUE);
                        mOverlays.add(ol1);
                    }
                    Overlay ol2 = new MyOverlay(_activity,destGeoPoint,destGeoPoint,3);
                    mOverlays.add(ol2);

                    progressDialog.dismiss();
                }else{
                    showAlert("Unable to find the route");
                }

                Overlay ol2 = new MyOverlay(_activity,destGeoPoint,destGeoPoint,3);
                mOverlays.add(ol2);
                progressDialog.dismiss();
                mapView.scrollBy(-1,-1);
                mapView.scrollBy(1,1);
            }else{
                showAlert("Unable to find the route");
            }

        }

    } //end Async
    Document doc = null;
    private void fetchData()
    {

        StringBuilder urlString = new StringBuilder();
        urlString.append("http://maps.google.com/maps/api/directions/xml?origin=");
        urlString.append( Double.toString((double)srcGeoPoint.getLatitudeE6()/1.0E6 ));
        urlString.append(",");
        urlString.append( Double.toString((double)srcGeoPoint.getLongitudeE6()/1.0E6 ));
        urlString.append("&destination=");//to
        urlString.append( Double.toString((double)destGeoPoint.getLatitudeE6()/1.0E6 ));
        urlString.append(",");
        urlString.append( Double.toString((double)destGeoPoint.getLongitudeE6()/1.0E6 ));
        urlString.append("&sensor=true&mode=driving");    
        Log.d("url","::"+urlString.toString());
        HttpURLConnection urlConnection= null;
        URL url = null;
        try
        {
            url = new URL(urlString.toString());
            urlConnection=(HttpURLConnection)url.openConnection();
            urlConnection.setRequestMethod("GET");
            urlConnection.setDoOutput(true);
            urlConnection.setDoInput(true);
            urlConnection.connect();
            DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
            DocumentBuilder db = dbf.newDocumentBuilder();
            doc = (Document) db.parse(urlConnection.getInputStream());//Util.XMLfromString(response);
        }catch (MalformedURLException e){
            e.printStackTrace();
        }catch (IOException e){
            e.printStackTrace();
        }catch (ParserConfigurationException e){
            e.printStackTrace();
        }
        catch (SAXException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
    private List<GeoPoint> decodePoly(String encoded) {

        List<GeoPoint> poly = new ArrayList<GeoPoint>();
        int index = 0, len = encoded.length();
        int lat = 0, lng = 0;

        while (index < len) {
            int b, shift = 0, result = 0;
            do {
                b = encoded.charAt(index++) - 63;
                result |= (b & 0x1f) << shift;
                shift += 5;
            } while (b >= 0x20);
            int dlat = ((result & 1) != 0 ? ~(result >> 1) : (result >> 1));
            lat += dlat;

            shift = 0;
            result = 0;
            do {
                b = encoded.charAt(index++) - 63;
                result |= (b & 0x1f) << shift;
                shift += 5;
            } while (b >= 0x20);
            int dlng = ((result & 1) != 0 ? ~(result >> 1) : (result >> 1));
            lng += dlng;

            GeoPoint p = new GeoPoint((int) (((double) lat / 1E5) * 1E6),
                    (int) (((double) lng / 1E5) * 1E6));
            poly.add(p);
        }

        return poly;
    }
    private void showAlert(String message){
        AlertDialog.Builder alert = new AlertDialog.Builder(_activity);
        alert.setTitle("Error");
        alert.setCancelable(false);
        alert.setMessage(message);
        alert.setPositiveButton("Ok",new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog, int which) {
                // TODO Auto-generated method stub

            }
        });
        alert.show();
    }


    private Drawable getDrawable(String fileName){
        return Drawable.createFromStream(_activity.getClass().getClassLoader().getResourceAsStream(fileName), "pin");
    }


}

这是适用于智能手机 Galaxy Nexus、android 4.2 的应用程序。我在我的平板电脑 android 4.0.2 上测试过，效果很好。但是当我在智能手机上测试它时，它崩溃了。我尝试将 LocationManager.NETWORK_PROVIDER 更改为 LocationManager.GPS_PROVIDER 但它还是崩溃了。我无法解决这个问题。谁能帮帮我？

Answer 1

我为同样的问题苦苦挣扎了几个小时。同一段代码在我的 Android 2.7 设备上运行良好，但不适用于我的 Android 4.1.1。最终，我发现，由于某些原因，如果没有首先调用 requestLocationUpdates()，getLastKnownLocation() 将不起作用。结果，我的 LocationListener 在我输入这两行后开始更新:

locationManager.requestLocationUpdates(provider, 1000, 10, locationListener);
Location location = locationManager.getLastKnownLocation(provider);

希望对您有所帮助。