android google map finding distance

Question

I am trying to find distance between two locations. I have longitudes and latitudes and I can calculate Euclidean distance. But I want to find road distance. I mean, , I want to calculate the distance of the road that I am going on while going to destination from source. In this case how to calculate this?

Answer 1

The easiest way would be to use the Google Directions API to get the directions, this gives you a list of all the points along the route (and the total distance).

Check out : http://code.google.com/apis/maps/documentation/directions/

If your not sure how to do this let me know and i'll post some code for you which will get the directions from google and extract the data you need.

UPDATE - CODE AS REQUESTED

private void GetDistance(GeoPoint src, GeoPoint dest) {

    StringBuilder urlString = new StringBuilder();
    urlString.append("http://maps.googleapis.com/maps/api/directions/json?");
    urlString.append("origin=");//from
    urlString.append( Double.toString((double)src.getLatitudeE6() / 1E6));
    urlString.append(",");
    urlString.append( Double.toString((double)src.getLongitudeE6() / 1E6));
    urlString.append("&destination=");//to
    urlString.append( Double.toString((double)dest.getLatitudeE6() / 1E6));
    urlString.append(",");
    urlString.append( Double.toString((double)dest.getLongitudeE6() / 1E6));
    urlString.append("&mode=walking&sensor=true");
    Log.d("xxx","URL="+urlString.toString());

    // get the JSON And parse it to get the directions data.
    HttpURLConnection urlConnection= null;
    URL url = null;

    url = new URL(urlString.toString());
    urlConnection=(HttpURLConnection)url.openConnection();
    urlConnection.setRequestMethod("GET");
    urlConnection.setDoOutput(true);
    urlConnection.setDoInput(true);
    urlConnection.connect();

    InputStream inStream = urlConnection.getInputStream();
    BufferedReader bReader = new BufferedReader(new InputStreamReader(inStream));

    String temp, response = "";
    while((temp = bReader.readLine()) != null){
        //Parse data
        response += temp;
    }
    //Close the reader, stream & connection
    bReader.close();
    inStream.close();
    urlConnection.disconnect();

    //Sortout JSONresponse 
    JSONObject object = (JSONObject) new JSONTokener(response).nextValue();
    JSONArray array = object.getJSONArray("routes");
        //Log.d("JSON","array: "+array.toString());

    //Routes is a combination of objects and arrays
    JSONObject routes = array.getJSONObject(0);
        //Log.d("JSON","routes: "+routes.toString());

    String summary = routes.getString("summary");
        //Log.d("JSON","summary: "+summary);

    JSONArray legs = routes.getJSONArray("legs");
        //Log.d("JSON","legs: "+legs.toString());

    JSONObject steps = legs.getJSONObject(0);
            //Log.d("JSON","steps: "+steps.toString());

    JSONObject distance = steps.getJSONObject("distance");
        //Log.d("JSON","distance: "+distance.toString());

            String sDistance = distance.getString("text");
            int iDistance = distance.getInt("value");

}

This will return the distance between the two points, you can change the function to return it as a string or as an integer, just return either sDistance or iDistance.

Hope this helps you, let me know if you need any more help.