谷歌地图显示错误的路线

Question

我有一张地图，我想在两点之间显示路线，问题是它总是显示我错误的路线。检查下面的图片，您将理解：

http://image.noelshack.com/fichiers/2014/21/1400859345-28297.jpg

这是我的代码： 用于获取路线的类： CalculItineraire.java：

package app.usthb;

import java.io.InputStream;
import java.net.URL;
import java.util.ArrayList;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;

import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;

import android.app.ProgressDialog;
import android.content.Context;
import android.graphics.Color;
import android.os.AsyncTask;
import android.widget.Toast;

import com.google.android.gms.maps.CameraUpdate;
import com.google.android.gms.maps.CameraUpdateFactory;
import com.google.android.gms.maps.GoogleMap;
import com.google.android.gms.maps.model.BitmapDescriptorFactory;
import com.google.android.gms.maps.model.LatLng;
import com.google.android.gms.maps.model.MarkerOptions;
import com.google.android.gms.maps.model.PolylineOptions;

public class CalculItineraire extends AsyncTask<Void, Integer, Boolean>{

    private ProgressDialog prog;

    private GoogleMap map;
    private Context context;
    private ArrayList<LatLng> list;
    private LatLng Source;
    private LatLng Destination;

    //=======================    Constructeur: 
    public CalculItineraire(GoogleMap map, Context context, LatLng Source, LatLng Destination){
        this.map = map;
        this.context = context;
        this.Source= Source;
        this.Destination = Destination;
        list =  new ArrayList<LatLng>();
    }


    @Override
    protected void onPreExecute(){
        //Toast.makeText(context, "Calcule de l'initéraire en cours...", Toast.LENGTH_LONG).show();
        prog = new ProgressDialog(context);
        prog.setMessage("Calcule de l'initéraire en cours...");
        prog.show();
    }



    @Override
    protected Boolean doInBackground(Void... params) {
        //Generation de l'url pour effectuer la requete:

        String url =  "http://maps.googleapis.com/maps/api/directions/xml?";
        url += "origin="+Source.latitude+","+Source.longitude;
        url += "&destination="+Destination.latitude+","+Source.longitude;
        url += "&sensor=false&units=metric&mode=walking";
        //Toast.makeText(context, url, Toast.LENGTH_LONG).show();
        try {
            //Lancer la requète: 
            InputStream in= new URL(url).openStream();
            //========  Recuperation de la requète:
            //Préparer le document a recevoir le resultat de la requète:
            DocumentBuilderFactory docBF = DocumentBuilderFactory.newInstance();
            docBF.setIgnoringComments(true);
            DocumentBuilder docB = docBF.newDocumentBuilder();
            final Document doc = docB.parse(in);
            doc.getDocumentElement().normalize();

            //Recuperer + tester  le statut de la requète: 
            String statut = doc.getElementsByTagName("status").item(0).getTextContent();
            if(!("OK".equals(statut))){
                //Si ce n'est pas OK, on sort de la methode avec false
                return false;
            }
            //=========== Recupéré les steps:
            final Element elementLeg = (Element) doc.getElementsByTagName("leg").item(0);
            NodeList ListStep = elementLeg.getElementsByTagName("step");

            for(int i=0; i<ListStep.getLength(); i++){
                Node Step = ListStep.item(i);
                //Cast de Step vers Element, pour pourvoir acceder au elements fils de Step
                Element ElementStep = (Element)Step;
                //Decoder le <Poin></Point>...
                this.decodePolylines(ElementStep.getElementsByTagName("points").item(0).getTextContent());
            }
            return true;

        } catch (Exception e) {
            return false;
        }
    }

    //Exception:
    private void processException()
    {
        Toast.makeText(context, "Exception!! ", Toast.LENGTH_LONG).show();
    }

    //onPostExecute!    
    protected void onPostExecute(Boolean result){
        //Onlever le Progress!
        prog.dismiss();

        if(!result){
            Toast.makeText(context, "result faux", 7000).show();
        }else{

            //Mise a jour de la carte:              
            //1. Ajouter un marker ROUGE pour le Depart:
            MarkerOptions MarkerDp = new MarkerOptions();
            MarkerDp.position(Source);
            MarkerDp.icon(BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_RED));

            //2. le Polyline:
            PolylineOptions polyline = new PolylineOptions();
            polyline.color(Color.CYAN);
            for(LatLng ltlg : list){
                //Toast.makeText(context, "and we have: "+ltlg.toString(), Toast.LENGTH_LONG).show();
                polyline.add(ltlg);
            }

            //3. Ajouter un marker BLEU pour la destination:
            MarkerOptions MarkerDs = new MarkerOptions();
            MarkerDs.position(Destination);
            MarkerDs.icon(BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_BLUE));

            //4. Mise a jour de la carte + camera :
            CameraUpdate update = CameraUpdateFactory.newLatLngZoom(Source, 14);
            map.moveCamera(update);
            map.addMarker(MarkerDp);
            map.addPolyline(polyline);
            map.addMarker(MarkerDs);
        }
    }


    /**
    * Méthode qui décode les points en latitude et longitudes
    * Créer par http://jeffreysambells.com/
    * full link: http://jeffreysambells.com/2010/05/27/decoding-polylines-from-google-maps-direction-api-with-java
    * @param points
    */
    private void decodePolylines(final String encodedPoints) {
        int index = 0;
        int lat = 0, lng = 0;

        while (index < encodedPoints.length()) {
            int b, shift = 0, result = 0;

            do {
                b = encodedPoints.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 = encodedPoints.charAt(index++) - 63;
                result |= (b & 0x1f) << shift;
                shift += 5;
            } while (b >= 0x20);

            int dlng = ((result & 1) != 0 ? ~(result >> 1) : (result >> 1));
            lng += dlng;

            list.add(new LatLng((double)lat/1E5, (double)lng/1E5));
        }
    }
}

从主班获得rtoue：

new CalculItineraire(map, this, new LatLng(36.7146905, 3.17872614), new LatLng(36.71377454, 3.17724288)).execute();