Create an external class to draw routes on android

Question

I would like to draw a route between two points on Android. I have already found how to make it in the main activity (I use the DirectionsJSONParser class I found on stackoverflow).

Yet, I want to draw many routes, so that it would be better if I would create an other class.

My dream would be to have this MainActivity :

public class MainActivity extends Activity {

GoogleMap map;
LatLng origin1;
LatLng origin2;
LatLng destination1;
LatLng destination2;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    // definition of origin1, origin2, destination1, destination2   

    ...

    // here the call to the missing class ClassDrawingPath
    PolylineOptions path1 = new ClassDrawingPath (origin1,destination1);
    PolylineOptions path2 = new ClassDrawingPath (origin2,destination2);

    gMap.addPolyline(path1);
    gMap.addPolyline(path2);

}

}

I copy the source files MainActity and DirectionsJSONParser, but you understand I don't want the same activity with color markers, I just want to get a "PolylineOptions" return.

package example;

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 gMap;
    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;
    }   
}

And

package example;

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;
    }
}

Thanks for your help :)

Answer 1

I followed this answer to create a class to draw directions. With a little customizations it is really useful. I managed to draw a polyline on the map and to get the list of the directions..