Archive for June, 2013

Guide: Google Maps V2 for Android: Draw Driving Direction on Map:

This is again one of those popular questions that I stumble upon, I already gave here an
answer for this one, but I decided to put it in here anyways as a post. So let get started.
First of all if you are not familiar with Google’s new Maps API, I suggest you to first of all read
this post: Google Maps API V2 Key to get your own API key which is required to
integrate Google maps in your application. Next follow this post: Google Maps API V2
to actually integrate Google Maps in your application.

If you already have a map integrated in your application and you want to add driving navigation
to it, you came to the right place. Here I will present you the code that will allow you to paint a line
(Polyline object on your map) to show the directions from point A to B. But first I would like
to point your to this quote:

Google Maps/Google Earth APIs Terms of Service

  Last updated: May 27, 2009
...
10. License Restrictions. Except as expressly permitted under the Terms, or unless you
have received prior written authorization from Google (or, as applicable, from the
provider of particular Content), Google's licenses above are subject to your adherence
to all of the restrictions below. Except as explicitly permitted in Section 7 or the
Maps APIs Documentation, you must not (nor may you permit anyone else to):
...
10.9 use the Service or Content with any products, systems, or applications for or in
connection with:

(a) real time navigation or route guidance, including but not limited to turn-by-turn
route guidance that is synchronized to the position of a user's sensor-enabled device;

and may be disabled for certain apps (somehow, at least on Android)... FromGeocode
scraping in .NET conversation:
This is not allowed by the API terms of use. You should not scrape Google Maps to
generate geocodes. We will block services that do automated queries of our servers.

Bret Taylor
Product Manager, Google Maps

I might be mistaken but from my understanding of this quote Google does not allow to show
driving navigation using Google Maps. Now that we covered that I will show you how you can
paint on the map.

1. So lets start with the GMapV2Direction class, this class is responsible to
make a request to Google Directions API and get the navigation instruction for 2 LatLng points:

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=" + mode;

        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(0);
        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(0);
        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(0);
        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(0);
        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 getDirection (Document doc) {
        NodeList nl1, nl2, nl3;
        ArrayList listGeopoints = new ArrayList();
        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 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 decodePoly(String encoded) {
        ArrayList poly = new ArrayList();
        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;
    }
}

2. Because finding the desired route is a potentially long running task,
we need to place this in a AsyncTask in order to avoid blocking the UI-Thread.
So we are going to create the following GetDirectionsAsyncTask:

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();
    }
}

3. No we would like to use this AsyncTask to find the road direction from one
location to another. To make the usage of this AsyncTask a little bit more convenient I have
created the following findDirections method in my MapFragmentActivity:

public void findDirections(double fromPositionDoubleLat, double fromPositionDoubleLong, double toPositionDoubleLat, double toPositionDoubleLong, String mode)
{
    Map<String, String> map = new HashMap<String, String>();
    map.put(GetDirectionsAsyncTask.USER_CURRENT_LAT, String.valueOf(fromPositionDoubleLat));
    map.put(GetDirectionsAsyncTask.USER_CURRENT_LONG, String.valueOf(fromPositionDoubleLong));
    map.put(GetDirectionsAsyncTask.DESTINATION_LAT, String.valueOf(toPositionDoubleLat));
    map.put(GetDirectionsAsyncTask.DESTINATION_LONG, String.valueOf(toPositionDoubleLong));
    map.put(GetDirectionsAsyncTask.DIRECTIONS_MODE, mode);

    GetDirectionsAsyncTask asyncTask = new GetDirectionsAsyncTask(this);
    asyncTask.execute(map);
}

What I’m doing here is creating a HashMap with the needed coordinates
(Start Lat and Long, End Lat and Long), Passing them to the AsyncTask and executing it.

4. Next, we will create the following handleGetDirectionsResult method,
to handle the AsyncTask result and to actually paint the directions Polyline on the map.

public void handleGetDirectionsResult(ArrayList directionPoints)
{
    Polyline newPolyline;
    GoogleMap mMap = ((SupportMapFragment)getSupportFragmentManager().findFragmentById(R.id.map)).getMap();
    PolylineOptions rectLine = new PolylineOptions().width(3).color(Color.BLUE);
    for(int i = 0 ; i < directionPoints.size() ; i++)
    {
        rectLine.add(directionPoints.get(i));
    }
    newPolyline = mMap.addPolyline(rectLine);
}

5. Finally to get the direction we need to run the findDirections method
with the desired locations in code like this:

findDirections(SGTasksListAppObj.getInstance().currentUserLocation.getLatitude(),
SGTasksListAppObj.getInstance().currentUserLocation.getLongitude(),
clickMarkerLatLng.latitude, clickMarkerLatLng.longitude, GMapV2Direction.MODE_DRIVING );

The final result should look something like that:

direction_blue

As you see a blue directions line is drown on the map, for showing the way you need to
go for your destination. And that’s it, you are finished.

6. UPDATE: Due to many requests I have created a small Android project that
demonstrates the usage of this code. You can download this project from here.
The project show how to navigate from Amsterdam to Paris or to Frankfurt, just
remember to add your Google Maps API V2 Key in the manifest file.

Enjoy and stay tuned.