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.
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.
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.
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:
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.
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the for loop in onPostExecute isnt getting executed. Please tell me how.
- Anirudh Kaluri
i didn’t find DirectionsJSONParser file
- lathiya bhautik
Every thing is great, but it doesnt zooms at current location… How to do that?? Please reply ASAP !
- kana
Hello. thx for your great post. How can i add more than one location and add polyline for it ?
- Amin
Hi, Can we mark for more than one locations?
- Emil
i found error here, Error:Execution failed for task ‘:app:transformClassesWithDexForDebug’. > com.android.build.api.transform.TransformException: com.android.ide.common.process.ProcessException: java.util.concurrent.ExecutionException: com.android.dex.DexIndexOverflowException: method ID not in [0, 0xffff]: 65536 what must i do …?
- fajarra
Cant see a directional route between my marker points…getting a straight line instead… Please help me fix the issue
- Sjhivani
nice and clean . thanks
- erfan
For me the route is not getting drawn, what could be the issue?
- Amrut
Where is DirectionJsonparser.java code?
- Keshav