Android Java Class for showing directions between origin location and destination location with Gmap V2 Direction.

async.java

 public class GetDirectionsAsyncTask extends AsyncTask<Map<String, String>, Object, ArrayList>
{
    public static final String USER_CURRENT_LAT = "user_current_lat";
    public static final String USER_CURRENT_LONG = "user_current_long";
    public static final String DESTINATION_LAT = "destination_lat";
    public static final String DESTINATION_LONG = "destination_long";
    public static final String DIRECTIONS_MODE = "directions_mode";
    private MapFragmentActivity activity;
    private Exception exception;
    private ProgressDialog progressDialog;
 
    public GetDirectionsAsyncTask(MapFragmentActivity activity)
    {
        super();
        this.activity = activity;
    }
 
    public void onPreExecute()
    {
        progressDialog = new ProgressDialog(activity);
        progressDialog.setMessage("Calculating directions");
        progressDialog.show();
    }
 
    @Override
    public void onPostExecute(ArrayList result)
    {
        progressDialog.dismiss();
        if (exception == null)
        {
            activity.handleGetDirectionsResult(result);
        }
        else
        {
            processException();
        }
    }
 
    @Override
    protected ArrayList doInBackground(Map<String, String>... params)
    {
        Map<String, String> paramMap = params[0];
        try
        {
            LatLng fromPosition = new LatLng(Double.valueOf(paramMap.get(USER_CURRENT_LAT)) , Double.valueOf(paramMap.get(USER_CURRENT_LONG)));
            LatLng toPosition = new LatLng(Double.valueOf(paramMap.get(DESTINATION_LAT)) , Double.valueOf(paramMap.get(DESTINATION_LONG)));
            GMapV2Direction md = new GMapV2Direction();
            Document doc = md.getDocument(fromPosition, toPosition, paramMap.get(DIRECTIONS_MODE));
            ArrayList directionPoints = md.getDirection(doc);
            return directionPoints;
        }
        catch (Exception e)
        {
            exception = e;
            return null;
        }
    }
 
    private void processException()
    {
        Toast.makeText(activity, activity.getString(R.string.error_when_retrieving_data), 3000).show();
    }
}

direction.java

LatLng fromPosition = new LatLng(13.687140112679154, 100.53525868803263);
LatLng toPosition = new LatLng(13.683660045847258, 100.53900808095932);

GoogleMap mMap = ((SupportMapFragment)getSupportFragmentManager()
        .findFragmentById(R.id.map)).getMap();
GMapV2Direction md = new GMapV2Direction();

Document doc = md.getDocument(fromPosition, toPosition, GMapV2Direction.MODE_DRIVING);
ArrayList<LatLng> directionPoint = md.getDirection(doc);
PolylineOptions rectLine = new PolylineOptions().width(3).color(Color.RED);

for(int i = 0 ; i < directionPoint.size() ; i++) {          
rectLine.add(directionPoint.get(i));
}

mMap.addPolyline(rectLine);

GMapV2Direction.java

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

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

import org.apache.http.HttpResponse;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.protocol.BasicHttpContext;
import org.apache.http.protocol.HttpContext;
import org.w3c.dom.Document;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;

import com.google.android.gms.maps.model.LatLng;

import android.content.Context;
import android.util.Log;

public class GMapV2Direction {
    public final static String MODE_DRIVING = "driving";
    public final static String MODE_WALKING = "walking";

    public GMapV2Direction() { }

    public Document getDocument(LatLng start, LatLng end, String mode) {
        String url = "http://maps.googleapis.com/maps/api/directions/xml?" 
                + "origin=" + start.latitude + "," + start.longitude  
                + "&destination=" + end.latitude + "," + end.longitude 
                + "&sensor=false&units=metric&mode=driving";

        try {
            HttpClient httpClient = new DefaultHttpClient();
            HttpContext localContext = new BasicHttpContext();
            HttpPost httpPost = new HttpPost(url);
            HttpResponse response = httpClient.execute(httpPost, localContext);
            InputStream in = response.getEntity().getContent();
            DocumentBuilder builder = DocumentBuilderFactory.newInstance().newDocumentBuilder();
            Document doc = builder.parse(in);
            return doc;
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }

    public String getDurationText (Document doc) {
        NodeList nl1 = doc.getElementsByTagName("duration");
        Node node1 = nl1.item(nl1.getLength() - 1);
        NodeList nl2 = node1.getChildNodes();
        Node node2 = nl2.item(getNodeIndex(nl2, "text"));
        Log.i("DurationText", node2.getTextContent());
        return node2.getTextContent();
    }

    public int getDurationValue (Document doc) {
        NodeList nl1 = doc.getElementsByTagName("duration");
        Node node1 = nl1.item(nl1.getLength() - 1);
        NodeList nl2 = node1.getChildNodes();
        Node node2 = nl2.item(getNodeIndex(nl2, "value"));
        Log.i("DurationValue", node2.getTextContent());
        return Integer.parseInt(node2.getTextContent());
    }

    public String getDistanceText (Document doc) {
        NodeList nl1 = doc.getElementsByTagName("distance");
        Node node1 = nl1.item(nl1.getLength() - 1);
        NodeList nl2 = node1.getChildNodes();
        Node node2 = nl2.item(getNodeIndex(nl2, "text"));
        Log.i("DistanceText", node2.getTextContent());
        return node2.getTextContent();
    }

    public int getDistanceValue (Document doc) {
        NodeList nl1 = doc.getElementsByTagName("distance");
        Node node1 = nl1.item(nl1.getLength() - 1);
        NodeList nl2 = node1.getChildNodes();
        Node node2 = nl2.item(getNodeIndex(nl2, "value"));
        Log.i("DistanceValue", node2.getTextContent());
        return Integer.parseInt(node2.getTextContent());
    }

    public String getStartAddress (Document doc) {
        NodeList nl1 = doc.getElementsByTagName("start_address");
        Node node1 = nl1.item(0);
        Log.i("StartAddress", node1.getTextContent());
        return node1.getTextContent();
    }

    public String getEndAddress (Document doc) {
        NodeList nl1 = doc.getElementsByTagName("end_address");
        Node node1 = nl1.item(0);
        Log.i("StartAddress", node1.getTextContent());
        return node1.getTextContent();
    }

    public String getCopyRights (Document doc) {
        NodeList nl1 = doc.getElementsByTagName("copyrights");
        Node node1 = nl1.item(0);
        Log.i("CopyRights", node1.getTextContent());
        return node1.getTextContent();
    }

    public ArrayList<LatLng> getDirection (Document doc) {
        NodeList nl1, nl2, nl3;
        ArrayList<LatLng> listGeopoints = new ArrayList<LatLng>();
        nl1 = doc.getElementsByTagName("step");
        if (nl1.getLength() > 0) {
            for (int i = 0; i < nl1.getLength(); i++) {
                Node node1 = nl1.item(i);
                nl2 = node1.getChildNodes();

                Node locationNode = nl2.item(getNodeIndex(nl2, "start_location"));
                nl3 = locationNode.getChildNodes();
                Node latNode = nl3.item(getNodeIndex(nl3, "lat"));
                double lat = Double.parseDouble(latNode.getTextContent());
                Node lngNode = nl3.item(getNodeIndex(nl3, "lng"));
                double lng = Double.parseDouble(lngNode.getTextContent());
                listGeopoints.add(new LatLng(lat, lng));

                locationNode = nl2.item(getNodeIndex(nl2, "polyline"));
                nl3 = locationNode.getChildNodes();
                latNode = nl3.item(getNodeIndex(nl3, "points"));
                ArrayList<LatLng> arr = decodePoly(latNode.getTextContent());
                for(int j = 0 ; j < arr.size() ; j++) {
                    listGeopoints.add(new LatLng(arr.get(j).latitude, arr.get(j).longitude));
                }

                locationNode = nl2.item(getNodeIndex(nl2, "end_location"));
                nl3 = locationNode.getChildNodes();
                latNode = nl3.item(getNodeIndex(nl3, "lat"));
                lat = Double.parseDouble(latNode.getTextContent());
                lngNode = nl3.item(getNodeIndex(nl3, "lng"));
                lng = Double.parseDouble(lngNode.getTextContent());
                listGeopoints.add(new LatLng(lat, lng));
            }
        }

        return listGeopoints;
    }

    private int getNodeIndex(NodeList nl, String nodename) {
        for(int i = 0 ; i < nl.getLength() ; i++) {
            if(nl.item(i).getNodeName().equals(nodename))
                return i;
        }
        return -1;
    }

    private ArrayList<LatLng> decodePoly(String encoded) {
        ArrayList<LatLng> poly = new ArrayList<LatLng>();
        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;

            LatLng position = new LatLng((double) lat / 1E5, (double) lng / 1E5);
            poly.add(position);
        }
        return poly;
    }
}