Find route with Androids Google Maps API

Question

I want to be able to display the route between two user-defined geographical points using the Google Maps API for Android. I also want to be ab

Answer 1

Here's some code to help you.

String url= 
"http://maps.googleapis.com/maps/api/directions/json?origin=" 
+ origin.latitude + "," + origin.longitude +"&destination=" 
+ destination.latitude + "," + destination.longitude + "&sensor=false";

To fetch the data with androidhttpclient, do something like this:

HttpResponse response;
HttpGet request;
AndroidHttpClient client = AndroidHttpClient.newInstance("somename");

request = new HttpGet(url);
response = client.execute(request);

InputStream source = response.getEntity().getContent();
String returnValue = buildStringIOutils(source);

return returnValue;

where buildStringIOUtils is:

private String buildStringIOutils(InputStream is) {
    try {
        return IOUtils.toString(is, "UTF-8");
    } catch (IOException e) {
        e.printStackTrace();
        return null;
    }
}

You can then extract the actual polyline from the JSON-response with something like this:

JSONObject result = new JSONObject(returnValue);
JSONArray routes = result.getJSONArray("routes");

                    long distanceForSegment = routes.getJSONObject(0).getJSONArray("legs").getJSONObject(0).getJSONObject("distance").getInt("value");

                    JSONArray steps = routes.getJSONObject(0).getJSONArray("legs")
                            .getJSONObject(0).getJSONArray("steps");

                    List lines = new ArrayList();

                    for(int i=0; i < steps.length(); i++) {
                        String polyline = steps.getJSONObject(i).getJSONObject("polyline").getString("points");

                        for(LatLng p : decodePolyline(polyline)) {
                            lines.add(p);
                        }
                    }

where the method decodePolyline is this:

    /** POLYLINE DECODER - http://jeffreysambells.com/2010/05/27/decoding-polylines-from-google-maps-direction-api-with-java **/
    private List decodePolyline(String encoded) {

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

        return poly;
    }

You can then add the polyline to the map with this:

Polyline polylineToAdd = mMap.addPolyline(new PolylineOptions().addAll(lines).width(3).color(Color.RED));

To change mode, add this to the url (See https://developers.google.com/maps/documentation/directions/): &mode=YOUR_MODE

driving (default) indicates standard driving directions using the road network.

walking requests walking directions via pedestrian paths & sidewalks (where available).

bicycling requests bicycling directions via bicycle paths & preferred streets (where available).

transit requests directions via public transit routes (where available).

Edit: About the "I would also like to get traffic information such as busy routes, congestion, etc." I have not looked into this, but my code should get you started pretty good.

Edit2: Found this in the google directions api: "For Driving Directions: Maps for Business customers can specify the departure_time to receive trip duration considering current traffic conditions. The departure_time must be set to within a few minutes of the current time."