Drawing driving route directions between two locations using Google Directions in Google Map Android API V2

by

Karthikeyan R

In this article, we will develop an Android application which facilitates users to tap two locations in the Google Map. On taping the second point, a driving route will be drawn in the Google Map Android API V2 using Google Directions API.

This application is developed in Eclipse (4.2.1) with ADT plugin (21.1.0) and Android SDK (21.1.0) and tested in a real device (Android 2.3.6  -  GingerBread ).

Get the API key for Google Maps Android API V2

We need to get an API key from Google to use Google Maps in Android application.

Please follow the given below link to get the API key for Google Maps Android API v2.

https://developers.google.com/maps/documentation/android/start

Add Android Support library to this project

By default, Android support library (android-support-v4.jar ) is added to this project by Eclipse IDE to the directory libs. If it is not added, we can do it manually by doing the following steps :

• Open Project Explorer by Clicking “Window -> Show View -> Project Explorer”
• Right click this project
• Then from popup menu, Click “Android Tools -> Add Support Library “

Update the layout file res/layout/activity_main.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"

    xmlns:tools="http://schemas.android.com/tools"

    android:layout_width="match_parent"

    android:layout_height="match_parent"

    tools:context=".MainActivity" >

    <fragment

        android:id="@+id/map"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        class="com.google.android.gms.maps.SupportMapFragment" />

</RelativeLayout>

Create a new class namely “DirectionsJSONParser” in the file src/in/wptrafficanalyzer/locationroutedirectionmapv2/DirectionsJSONParser.java

package in.wptrafficanalyzer.locationroutedirectionmapv2;

import java.util.ArrayList;

import java.util.HashMap;

import java.util.List;

import org.json.JSONArray;

import org.json.JSONException;

import org.json.JSONObject;

import com.google.android.gms.maps.model.LatLng;

public class DirectionsJSONParser {

    /** Receives a JSONObject and returns a list of lists containing latitude and longitude */

    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");

            /** Traversing all routes */

            for(int i=0;i<jRoutes.length();i++){

                jLegs = ( (JSONObject)jRoutes.get(i)).getJSONArray("legs");

                List path = new ArrayList<HashMap<String, String>>();

                /** Traversing all legs */

                for(int j=0;j<jLegs.length();j++){

                    jSteps = ( (JSONObject)jLegs.get(j)).getJSONArray("steps");

                    /** Traversing all 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);

                        /** Traversing all points */

                        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 (JSONException e) {

        e.printStackTrace();

    }catch (Exception e){

    }

    return routes;

    }

    /**

    * Method to decode polyline points

    * Courtesy : http://jeffreysambells.com/2010/05/27/decoding-polylines-from-google-maps-direction-api-with-java

    * */

    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;

    }

}

Update the class “MainActivity” in the file src/in/wptrafficanalyzer/locationroutedirectionmapv2/MainActivity.java

package in.wptrafficanalyzer.locationroutedirectionmapv2;

import java.io.BufferedReader;

import java.io.IOException;

import java.io.InputStream;

import java.io.InputStreamReader;

import java.net.HttpURLConnection;

import java.net.URL;

import java.util.ArrayList;

import java.util.HashMap;

import java.util.List;

import org.json.JSONObject;

import android.graphics.Color;

import android.os.AsyncTask;

import android.os.Bundle;

import android.support.v4.app.FragmentActivity;

import android.util.Log;

import android.view.Menu;

import com.google.android.gms.maps.GoogleMap;

import com.google.android.gms.maps.GoogleMap.OnMapClickListener;

import com.google.android.gms.maps.SupportMapFragment;

import com.google.android.gms.maps.model.BitmapDescriptorFactory;

import com.google.android.gms.maps.model.LatLng;

import com.google.android.gms.maps.model.MarkerOptions;

import com.google.android.gms.maps.model.PolylineOptions;

public class MainActivity extends FragmentActivity {

    GoogleMap map;

    ArrayList<LatLng> markerPoints;

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        // Initializing

        markerPoints = new ArrayList<LatLng>();

        // Getting reference to SupportMapFragment of the activity_main

        SupportMapFragment fm = (SupportMapFragment)getSupportFragmentManager().findFragmentById(R.id.map);

        // Getting Map for the SupportMapFragment

        map = fm.getMap();

        if(map!=null){

            // Enable MyLocation Button in the Map

            map.setMyLocationEnabled(true);

            // Setting onclick event listener for the map

            map.setOnMapClickListener(new OnMapClickListener() {

                @Override

                public void onMapClick(LatLng point) {

                    // Already two locations

                    if(markerPoints.size()>1){

                        markerPoints.clear();

                        map.clear();

                    }

                    // Adding new item to the ArrayList

                    markerPoints.add(point);

                    // Creating MarkerOptions

                    MarkerOptions options = new MarkerOptions();

                    // Setting the position of the marker

                    options.position(point);

                    /**

                    * For the start location, the color of marker is GREEN and

                    * for the end location, the color of marker is RED.

                    */

                    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

                    map.addMarker(options);

                    // Checks, whether start and end locations are captured

                    if(markerPoints.size() >= 2){

                        LatLng origin = markerPoints.get(0);

                        LatLng dest = 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 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";

        // 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;

    }

    /** A method to download json data from url */

    private String downloadUrl(String strUrl) throws IOException{

        String data = "";

        InputStream iStream = null;

        HttpURLConnection urlConnection = null;

        try{

            URL url = new URL(strUrl);

            // Creating an http connection to communicate with url

            urlConnection = (HttpURLConnection) url.openConnection();

            // Connecting to url

            urlConnection.connect();

            // Reading data from url

            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 downloading url", e.toString());

        }finally{

            iStream.close();

            urlConnection.disconnect();

        }

        return data;

    }

    // Fetches data from url passed

    private class DownloadTask extends AsyncTask<String, Void, String>{

        // Downloading data in non-ui thread

        @Override

        protected String doInBackground(String... url) {

            // For storing data from web service

            String data = "";

            try{

                // Fetching the data from web service

                data = downloadUrl(url[0]);

            }catch(Exception e){

                Log.d("Background Task",e.toString());

            }

            return data;

        }

        // Executes in UI thread, after the execution of

        // doInBackground()

        @Override

        protected void onPostExecute(String result) {

            super.onPostExecute(result);

            ParserTask parserTask = new ParserTask();

            // Invokes the thread for parsing the JSON data

            parserTask.execute(result);

        }

    }

    /** A class to parse the Google Places in JSON format */

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

        // Parsing the data in non-ui thread

        @Override

        protected List<List<HashMap<String, String>>> doInBackground(String... jsonData) {

            JSONObject jObject;

            List<List<HashMap<String, String>>> routes = null;

            try{

                jObject = new JSONObject(jsonData[0]);

                DirectionsJSONParser parser = new DirectionsJSONParser();

                // Starts parsing data

                routes = parser.parse(jObject);

            }catch(Exception e){

                e.printStackTrace();

            }

            return routes;

        }

        // Executes in UI thread, after the parsing process

        @Override

        protected void onPostExecute(List<List<HashMap<String, String>>> result) {

            ArrayList<LatLng> points = null;

            PolylineOptions lineOptions = null;

            MarkerOptions markerOptions = new MarkerOptions();

            // Traversing through all the routes

            for(int i=0;i<result.size();i++){

                points = new ArrayList<LatLng>();

                lineOptions = new PolylineOptions();

                // Fetching i-th route

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

                // Fetching all the points in i-th route

                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);

                }

                // Adding all the points in the route to LineOptions

                lineOptions.addAll(points);

                lineOptions.width(2);

                lineOptions.color(Color.RED);

            }

            // Drawing polyline in the Google Map for the i-th route

            map.addPolyline(lineOptions);

        }

    }

    @Override

    public boolean onCreateOptionsMenu(Menu menu) {

        // Inflate the menu; this adds items to the action bar if it is present.

        getMenuInflater().inflate(R.menu.main, menu);

        return true;

    }

}

Update the file AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>

<manifest xmlns:android="http://schemas.android.com/apk/res/android"

    package="in.wptrafficanalyzer.locationroutedirectionmapv2"

    android:versionCode="1"

    android:versionName="1.0" >

    <uses-sdk

        android:minSdkVersion="8"

        android:targetSdkVersion="17" />

    <uses-permission android:name="android.permission.INTERNET"/>

    <permission

        android:name="in.wptrafficanalyzer.locationroutedirectionmapv2.permission.MAPS_RECEIVE"

        android:protectionLevel="signature" />

    <uses-permission android:name="in.wptrafficanalyzer.locationroutedirectionmapv2.permission.MAPS_RECEIVE" />

    <uses-permission android:name="android.permission.INTERNET"/>

    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>

    <uses-permission android:name="com.google.android.providers.gsf.permission.READ_GSERVICES"/>

    <uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION"/>

    <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION"/>

    <uses-feature

        android:glEsVersion="0x00020000"

        android:required="true"/>

    <application

        android:allowBackup="true"

        android:icon="@drawable/ic_launcher"

        android:label="@string/app_name"

        android:theme="@style/AppTheme" >

        <activity

            android:name="in.wptrafficanalyzer.locationroutedirectionmapv2.MainActivity"

            android:label="@string/app_name" >

            <intent-filter>

                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />

            </intent-filter>

        </activity>

        <meta-data

            android:name="com.google.android.maps.v2.API_KEY"

            android:value="YOUR_API_KEY"/>

    </application>

</manifest>

Replace “YOUR_API_KEY” at the line 46 with the API key obtained  from Api Console