Path is sequence of point . One of the solution is to make HTTP request to Google maps API specifying your two locations as parameters and get back JSON describing the points required to make the path between the two points. Require code to do that are listed below :
- Get direction URL require to call Google Maps API
private String getMapsApiDirectionsUrl(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";
// Building the parameters to the web service
String parameters = str_origin+"&"+str_dest+"&"+sensor;
// 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;
}
Do the URL call in background
private class ReadTask extends AsyncTask<String, Void , String> {
@Override
protected String doInBackground(String... url) {
// TODO Auto-generated method stub
String data = "";
try {
MapHttpConnection http = new MapHttpConnection();
data = http.readUr(url[0]);
} catch (Exception e) {
// TODO: handle exception
Log.d("Background Task", e.toString());
}
return data;
}
@Override
protected void onPostExecute(String result) {
super.onPostExecute(result);
new ParserTask().execute(result);
}
}
public class MapHttpConnection {
public String readUr(String mapsApiDirectionsUrl) throws IOException{
String data = "";
InputStream istream = null;
HttpURLConnection urlConnection = null;
try {
URL url = new URL(mapsApiDirectionsUrl);
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 while reading url", e.toString());
} finally {
istream.close();
urlConnection.disconnect();
}
return data;
}
}
Create Parser class to parse the data from JSON to List of pointes
public class PathJSONParser {
public List<List<HashMap<String, String>>> parse(JSONObject jObject) {
List<List<HashMap<String, String>>> routes = new ArrayList<List<HashMap<String,String>>>();
JSONArray jRoutes = null;
JSONArray jLegs = null;
JSONArray jSteps = null;
try {
jRoutes = jObject.getJSONArray("routes");
for (int i=0 ; i < jRoutes.length() ; i ++) {
jLegs = ((JSONObject) jRoutes.get(i)).getJSONArray("legs");
List<HashMap<String, String>> path = new ArrayList<HashMap<String,String>>();
for(int j = 0 ; j < jLegs.length() ; j++) {
jSteps = ((JSONObject) jLegs.get(j)).getJSONArray("steps");
for(int k = 0 ; k < jSteps.length() ; k ++) {
String polyline = "";
polyline = (String) ((JSONObject) ((JSONObject) jSteps.get(k)).get("polyline")).get("points");
List<LatLng> list = decodePoly(polyline);
for(int l = 0 ; l < list.size() ; l ++){
HashMap<String, String> hm = new HashMap<String, String>();
hm.put("lat",
Double.toString(((LatLng) list.get(l)).latitude));
hm.put("lng",
Double.toString(((LatLng) list.get(l)).longitude));
path.add(hm);
}
}
routes.add(path);
}
}
} catch (Exception e) {
e.printStackTrace();
}
return routes;
}
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;
}}
Do the parse using another Thread to expand performance
private class ParserTask extends AsyncTask<String,Integer, List<List<HashMap<String , String >>>> {
@Override
protected List<List<HashMap<String, String>>> doInBackground(
String... jsonData) {
// TODO Auto-generated method stub
JSONObject jObject;
List<List<HashMap<String, String>>> routes = null;
try {
jObject = new JSONObject(jsonData[0]);
PathJSONParser parser = new PathJSONParser();
routes = parser.parse(jObject);
} catch (Exception e) {
e.printStackTrace();
}
return routes;
}
@Override
protected void onPostExecute(List<List<HashMap<String, String>>> routes) {
ArrayList<LatLng> points = null;
PolylineOptions polyLineOptions = null;
// traversing through routes
for (int i = 0; i < routes.size(); i++) {
points = new ArrayList<LatLng>();
polyLineOptions = new PolylineOptions();
List<HashMap<String, String>> path = routes.get(i);
for (int j = 0; j < path.size(); j++) {
HashMap<String, String> 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);
}
polyLineOptions.addAll(points);
polyLineOptions.width(4);
polyLineOptions.color(Color.BLUE);
}
googleMap.addPolyline(polyLineOptions);
}}
- When you want to get the path of two point
String url = getMapsApiDirectionsUrl(latlngOne, latlngTwo);
ReadTask downloadTask = new ReadTask();
// Start downloading json data from Google Directions API
downloadTask.execute(url);
To calculate distance between points
float[] results = new float[1];
Location.distanceBetween(latLongA.latitude, latLongB.longitude,
latLongB.latitude, latLongB.longitude,
results);
the results will be in meters
