Android Google Map – Drawing Route Between two points

In this tutorial, we’ll be creating an android application that draws a possible google map route between two points. We’ll be using Google Maps Directions API in our application.

Android Google Map – Drawing Route

Create a new Google Map API Key from the API console using the steps demonstrated in this tutorial.

Create a New Android Studio Project and select the template as Google Maps Activity. Add the API key inside the google_maps_api.xml file that resides inside debug->res->values folder

This is how the application should look if you’re using the latest Android Studio.

Android Google Maps Drawing Path Project Structure

The DirectionsJSONParser.java file is the one that parses the locations and returns the route. decodePoly() method is then invoked to get the polyline data that’s later drawn on the map.

Android Google Maps Drawing Route Code

The MainActivity.java code is given below.

public class MapsActivity extends FragmentActivity implements OnMapReadyCallback {

    private GoogleMap mMap;
    ArrayList markerPoints= new ArrayList();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_maps);
        // Obtain the SupportMapFragment and get notified when the map is ready to be used.
        SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager()
                .findFragmentById(R.id.map);
        mapFragment.getMapAsync(this);
    }

    @Override
    public void onMapReady(GoogleMap googleMap) {
        mMap = googleMap;
        LatLng sydney = new LatLng(-34, 151);
        //mMap.addMarker(new MarkerOptions().position(sydney).title("Marker in Sydney"));
        mMap.moveCamera(CameraUpdateFactory.newLatLngZoom(sydney, 16));

        mMap.setOnMapClickListener(new GoogleMap.OnMapClickListener() {
            @Override
            public void onMapClick(LatLng latLng) {

                if (markerPoints.size() > 1) {
                    markerPoints.clear();
                    mMap.clear();
                }

                // Adding new item to the ArrayList
                markerPoints.add(latLng);

                // Creating MarkerOptions
                MarkerOptions options = new MarkerOptions();

                // Setting the position of the marker
                options.position(latLng);

                if (markerPoints.size() == 1) {
                    options.icon(BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_GREEN));
                } else if (markerPoints.size() == 2) {
                    options.icon(BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_RED));
                }

                // Add new marker to the Google Map Android API V2
                mMap.addMarker(options);

                // Checks, whether start and end locations are captured
                if (markerPoints.size() >= 2) {
                    LatLng origin = (LatLng) markerPoints.get(0);
                    LatLng dest = (LatLng) markerPoints.get(1);

                    // Getting URL to the Google Directions API
                    String url = getDirectionsUrl(origin, dest);

                    DownloadTask downloadTask = new DownloadTask();

                    // Start downloading json data from Google Directions API
                    downloadTask.execute(url);
                }

            }
        });

    }

    private class DownloadTask extends AsyncTask {

        @Override
        protected String doInBackground(String... url) {

            String data = "";

            try {
                data = downloadUrl(url[0]);
            } catch (Exception e) {
                Log.d("Background Task", e.toString());
            }
            return data;
        }

        @Override
        protected void onPostExecute(String result) {
            super.onPostExecute(result);

            ParserTask parserTask = new ParserTask();


            parserTask.execute(result);

        }
    }

    private class ParserTask extends AsyncTask<String, Integer, List<List<HashMap>>> {

        // Parsing the data in non-ui thread
        @Override
        protected List<List<HashMap>> doInBackground(String... jsonData) {

            JSONObject jObject;
            List<List<HashMap>> routes = null;

            try {
                jObject = new JSONObject(jsonData[0]);
                DirectionsJSONParser parser = new DirectionsJSONParser();

                routes = parser.parse(jObject);
            } catch (Exception e) {
                e.printStackTrace();
            }
            return routes;
        }

        @Override
        protected void onPostExecute(List<List<HashMap>> result) {
            ArrayList points = null;
            PolylineOptions lineOptions = null;
            MarkerOptions markerOptions = new MarkerOptions();

            for (int i = 0; i < result.size(); i++) {
                points = new ArrayList();
                lineOptions = new PolylineOptions();

                List<HashMap> path = result.get(i);

                for (int j = 0; j < path.size(); j++) {
                    HashMap point = path.get(j);

                    double lat = Double.parseDouble(point.get("lat"));
                    double lng = Double.parseDouble(point.get("lng"));
                    LatLng position = new LatLng(lat, lng);

                    points.add(position);
                }

                lineOptions.addAll(points);
                lineOptions.width(12);
                lineOptions.color(Color.RED);
                lineOptions.geodesic(true);

            }

// Drawing polyline in the Google Map for the i-th route
            mMap.addPolyline(lineOptions);
        }
    }

    private String getDirectionsUrl(LatLng origin, LatLng dest) {

        // Origin of route
        String str_origin = "origin=" + origin.latitude + "," + origin.longitude;

        // Destination of route
        String str_dest = "destination=" + dest.latitude + "," + dest.longitude;

        // Sensor enabled
        String sensor = "sensor=false";
        String mode = "mode=driving";

        // Building the parameters to the web service
        String parameters = str_origin + "&" + str_dest + "&" + sensor + "&" + mode;

        // Output format
        String output = "json";

        // Building the url to the web service
        String url = "https://maps.googleapis.com/maps/api/directions/" + output + "?" + parameters;
        

        return url;
    }

    private String downloadUrl(String strUrl) throws IOException {
        String data = "";
        InputStream iStream = null;
        HttpURLConnection urlConnection = null;
        try {
            URL url = new URL(strUrl);

            urlConnection = (HttpURLConnection) url.openConnection();

            urlConnection.connect();

            iStream = urlConnection.getInputStream();

            BufferedReader br = new BufferedReader(new InputStreamReader(iStream));

            StringBuffer sb = new StringBuffer();

            String line = "";
            while ((line = br.readLine()) != null) {
                sb.append(line);
            }

            data = sb.toString();

            br.close();

        } catch (Exception e) {
            Log.d("Exception", e.toString());
        } finally {
            iStream.close();
            urlConnection.disconnect();
        }
        return data;
    }
}

We’ve called an onMapClickListener on the google map object. It’s used to set a marker on the clicked location and store that location in an ArrayList. The ArrayList is used to store the source and destination markers only.
The getDirectionsUrl() is called the Directions API URL with the output and parameters as shown below.

"https://maps.googleapis.com/maps/api/directions/" + output + "?" + parameters;

The output variable holds a “json” string and the parameter string is created as:
String parameters = str_origin + "&" + str_dest + "&" + sensor + "&" + mode;

We’ve set the mode=driving in the current application.
The other modes of transport are:

• driving (default)
• walking
• bicycling
• transit

The output of the application is given below:

This brings an end to this tutorial. You can download the final project from the link below, add your own Google Map API key.