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.
Table of Contents
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.
Hi , Im trying to understand your code since I am a beginner.
Why do I keep getting this runtime error:
java.lang.NullPointerException: Attempt to invoke interface method ‘int java.util.List.size()’ on a null object reference
it has something to do with result being null
Yes, you can’t call methods on a “null” object. Check if the object is initialized properly.
And how exactly to initialize it??
I am a beginner too and am getting the same issue. Some help would be greatly appreciated and thanked.
I want to draw route between two points in map.But as per the above code I could only select two points in map, the direction doesn’t came.
Is there any suggestions for me to solve .
Dear
I have gone through your tutorials of google map android. I am stuck to show journey route of train covered and remaining in two different colors. Second color overlapping on 1st one…
2nd issue it is showing alternative route which I coded alternatives=false also but still showing extra lines…
Please visit URL to have more information about issue…https://stackoverflow.com/questions/57495955/how-to-show-journey-of-train-reached-and-remaining-on-mobile-app
I want little help to sort these small issues…
polylineOptions = null
why is it empty?
I want to draw route between more than two points. How can i do that ? Is it possible with a single call ?
Any help with this?
java.lang.NullPointerException: PolylineOptions cannot be null.
at com.google.maps.api.android.lib6.common.n.a(:com.google.android.gms.dynamite_mapsdynamite@13280052@13.2.80 (040700-211705629):32)
at com.google.maps.api.android.lib6.impl.dm.(:com.google.android.gms.dynamite_mapsdynamite@13280052@13.2.80 (040700-211705629):6)
at com.google.maps.api.android.lib6.impl.bc.a(:com.google.android.gms.dynamite_mapsdynamite@13280052@13.2.80 (040700-211705629):80)
at com.google.android.gms.maps.internal.l.a(:com.google.android.gms.dynamite_mapsdynamite@13280052@13.2.80 (040700-211705629):501)
at fh.onTransact(:com.google.android.gms.dynamite_mapsdynamite@13280052@13.2.80 (040700-211705629):10)
at android.os.Binder.transact(Binder.java:667)
at com.google.android.gms.internal.maps.zza.transactAndReadException(Unknown Source:7)
at com.google.android.gms.maps.internal.zzg.addPolyline(Unknown Source:9)
at com.google.android.gms.maps.GoogleMap.addPolyline(Unknown Source:4)
at com.example.hb.navdrawerapp.SecondFragment$ParserTask.onPostExecute(SecondFragment.java:169)
at com.example.hb.navdrawerapp.SecondFragment$ParserTask.onPostExecute(SecondFragment.java:121)
at android.os.AsyncTask.finish(AsyncTask.java:695)
at android.os.AsyncTask.access$600(AsyncTask.java:180)
at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:712)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loop(Looper.java:193)
at android.app.ActivityThread.main(ActivityThread.java:6669)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)
Add your api key to url as mentioned below
String url = “https://maps.googleapis.com/maps/api/directions/” + output + “?” + parameters +”&key=” +”YOUR KEY”;
I want to use this inside fragment. I did this in my OnCreateView()-
View rootView=inflater.inflate(R.layout.image1,container,false);
mapFragment = (SupportMapFragment) getFragmentManager().findFragmentById(R.id.map);
mapFragment.getMapAsync(this);
return rootView;
And I am getting this error-
java.lang.NullPointerException: Attempt to invoke virtual method ‘void com.google.android.gms.maps.SupportMapFragment.getMapAsync(com.google.android.gms.maps.OnMapReadyCallback)’ on a null object reference
I am not getting an output. It just shows a map, that’s all.
Hi Anupam Chugh,
Could you tell me after drawing a map between two locations,how to update a user position with respect to his moment? Can you help me please…….. Thank you!
DirectionsJSONParser is missing.
Morning
when i run the app it crashes and the error points to this String str_dest = “destination=” + dest.latitude + “,” + dest.longitude;
Hi, you are really helped me, but I’m getting errors:
java.lang.NullPointerException: PolylineOptions cannot be null.
why is this error?
Please make sure that the class object is initialised properly.
Hi, Did you solved the problem?
I am also facing the same issue. I Just downloaded and code, added my key and ran it.
API Google now requires KEY for routes.
https://developers.google.com/maps/documentation/directions/get-api-key
this route key is free??
Here find some:
https://stackoverflow.com/questions/42996662/polylineoptions-cannot-be-null
Hi, the google directions have a cost?
if i can 8 or 9 time in add point in polylineoption then give error you can try
first get spinner and add 2 value driving and walking
that add in mode value
after select to change route
that selection 7 or 8 time i sure give the error
i am here just to say i love it, work on the first time
is there any way to get the distance from the route?
Use the Google Distance API
Where is DirectionJsonparser.java code?
For me the route is not getting drawn, what could be the issue?
same here brother
same here did you solved iT?
nice and clean . thanks
Cant see a directional route between my marker points…getting a straight line instead..
Please help me fix the issue
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 ..?
i solve my problem after migrate compileSdkVersion from 25 to 26. Thanks Anupam, its great….
please tell me i got same error how to solve it
firstly import this gradle :
compile ‘com.android.support:multidex:1.0.0’
then write
defaultConfig {
………………………..
…………………………
multiDexEnabled true
}
it should be help for you…..
Hi, Can we mark for more than one locations?
Hello. thx for your great post. How can i add more than one location and add polyline for it ?
sir,did you got the solution for adding more than one marker
Every thing is great, but it doesnt zooms at current location.. How to do that?? Please reply ASAP !
i didn’t find DirectionsJSONParser file
Download project from above link.
https://www.journaldev.com/?wpdmact=process&did=MjEzLmhvdGxpbms=
the for loop in onPostExecute isnt getting executed. Please tell me how.
Perhaps the direction result isn’t being returned. Maybe you haven’t enabled the Direction API
hello sir i use this code but result retrun 0 i also enable direction api but still polyline not draw
have u solved the issues