You can do this using the Google Maps API v2 for Android , and the Google Maps Directions webservice API
There are already many other good answers to get started with the Google Maps API. See here for a full working example of a simple Activity map. Please note that you will also need to get the API key configured to work with your project.
Regarding the use of the Google Maps Directions web services API, you should first read the documentation. You can use the API key and enable the API in your developer console, but it still works currently without using the API key.
Here is the basic code that you will need to use the Google Maps API to draw a polyline between two points, note that the points returned from the API are encoded in the encoded base string String, which must be decoded.
Firstly, here is AsyncTask that you should give two LatLng points when called.
You would call AsyncTask two LatLng objects, for example between two markers:
new GetDirectionsAsync().execute(markerOne.getPosition(), markerTwo.getPosition());
Here is the AsyncTask code:
class GetDirectionsAsync extends AsyncTask<LatLng, Void, List<LatLng>> { JSONParser jsonParser; String DIRECTIONS_URL = "https://maps.googleapis.com/maps/api/directions/json"; @Override protected void onPreExecute() { super.onPreExecute(); } @Override protected List<LatLng> doInBackground(LatLng... params) { LatLng start = params[0]; LatLng end = params[1]; HashMap<String, String> points = new HashMap<>(); points.put("origin", start.latitude + "," + start.longitude); points.put("destination", end.latitude + "," + end.longitude); jsonParser = new JSONParser(); JSONObject obj = jsonParser.makeHttpRequest(DIRECTIONS_URL, "GET", points, true); if (obj == null) return null; try { List<LatLng> list = null; JSONArray routeArray = obj.getJSONArray("routes"); JSONObject routes = routeArray.getJSONObject(0); JSONObject overviewPolylines = routes.getJSONObject("overview_polyline"); String encodedString = overviewPolylines.getString("points"); list = decodePoly(encodedString); return list; } catch (JSONException e) { e.printStackTrace(); } return null; } @Override protected void onPostExecute(List<LatLng> pointsList) { if (pointsList == null) return; if (line != null){ line.remove(); } PolylineOptions options = new PolylineOptions().width(5).color(Color.MAGENTA).geodesic(true); for (int i = 0; i < pointsList.size(); i++) { LatLng point = pointsList.get(i); options.add(point); } line = mMap.addPolyline(options); } }
AsyncTask refers to some Activity member variables, namely Polyline and GoogleMap, the definition of Activity will look like this:
public class MapsActivity extends AppCompatActivity implements OnMapReadyCallback{ GoogleMap mMap; Polyline line;
Here's the decodePoly () method used to decode the points:
private List<LatLng> decodePoly(String encoded) { List<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 p = new LatLng((((double) lat / 1E5)), (((double) lng / 1E5))); poly.add(p); } return poly; }
Here's the JSONParser class used in this example, note that this is a modified version updated for Android 23, that I wrote a blog post about :
public class JSONParser { String charset = "UTF-8"; HttpURLConnection conn; DataOutputStream wr; StringBuilder result; URL urlObj; JSONObject jObj = null; StringBuilder sbParams; String paramsString; public JSONObject makeHttpRequest(String url, String method, HashMap<String, String> params, boolean encode) { sbParams = new StringBuilder(); int i = 0; for (String key : params.keySet()) { try { if (i != 0){ sbParams.append("&"); } if (encode) { sbParams.append(key).append("=") .append(URLEncoder.encode(params.get(key), charset)); } else{ sbParams.append(key).append("=") .append(params.get(key)); } } catch (UnsupportedEncodingException e) { e.printStackTrace(); } i++; } if (method.equals("POST")) { // request method is POST try { urlObj = new URL(url); conn = (HttpURLConnection) urlObj.openConnection(); conn.setDoOutput(true); conn.setRequestMethod("POST"); conn.setRequestProperty("Accept-Charset", charset); conn.setReadTimeout(10000); conn.setConnectTimeout(15000); conn.connect(); paramsString = sbParams.toString(); wr = new DataOutputStream(conn.getOutputStream()); wr.writeBytes(paramsString); wr.flush(); wr.close(); } catch (IOException e) { e.printStackTrace(); } } else if(method.equals("GET")){ // request method is GET if (sbParams.length() != 0) { url += "?" + sbParams.toString(); } Log.d("JSONParser", "full GET url: " + url); try { urlObj = new URL(url); conn = (HttpURLConnection) urlObj.openConnection(); conn.setDoOutput(false); conn.setRequestMethod("GET"); conn.setRequestProperty("Accept-Charset", charset); conn.setConnectTimeout(15000); conn.connect(); } catch (IOException e) { e.printStackTrace(); } } try { //Receive the response from the server InputStream in = new BufferedInputStream(conn.getInputStream()); BufferedReader reader = new BufferedReader(new InputStreamReader(in)); String line; result = new StringBuilder(); while ((line = reader.readLine()) != null) { result.append(line); } Log.d("JSON Parser", "result: " + result.toString()); } catch (IOException e) { e.printStackTrace(); } conn.disconnect(); // try parse the string to a JSON object try { jObj = new JSONObject(result.toString()); } catch (JSONException e) { Log.e("JSON Parser", "Error parsing data " + e.toString()); } // return JSON Object return jObj; } }
The result of drawing a route between two markers:
