Why isn't a polyline drawn between points?

Question

Java

Good afternoon!
I am using google maps api to build my app. The code should route on the map using Polyline. However, the points are marked, the line does not work, what could be the problem? (code in spoiler)

The code

import android.graphics.Color;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import com.google.android.gms.maps.CameraUpdateFactory;
import com.google.android.gms.maps.GoogleMap;
import com.google.android.gms.maps.OnMapReadyCallback;
import com.google.android.gms.maps.SupportMapFragment;
import com.google.android.gms.maps.model.LatLng;
import com.google.android.gms.maps.model.MarkerOptions;
import com.google.android.gms.maps.model.PolylineOptions;
import org.json.JSONObject;
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 androidx.fragment.app.FragmentActivity;

public class MapsActivity extends FragmentActivity implements OnMapReadyCallback {

    private GoogleMap mMap;

    MarkerOptions origin, destination;


    @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);

        //Setting marker to draw route between these two points
        /**
         * later to use tracking for app combine gps_tracker part for getting coordinates every time but save origin point by making condition in a loop/saving points
         * **/
        origin = new MarkerOptions().position(new LatLng(51.58, 10.667)).title("Origin layout").snippet("origin");
        destination = new MarkerOptions().position(new LatLng(51.2904, 10.666)).title("Destination").snippet("destination");

        // Getting URL to the Google Directions API
        String url = getDirectionsUrl(origin.getPosition(), destination.getPosition());

        DownloadTask downloadTask = new DownloadTask();

        // Start downloading json data from Google Directions API
        downloadTask.execute(url);

    }

    @Override

    public void onMapReady(GoogleMap googleMap){
        mMap = googleMap;
        mMap.addMarker(origin);
        mMap.addMarker(destination);
        mMap.animateCamera(CameraUpdateFactory.newLatLngZoom(origin.getPosition(), 9));
    }
    private class DownloadTask extends AsyncTask<String, Void, String> {

        @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);
        }
    }

    /**
     * Class to parse the 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]);
                DataParser parser = new DataParser();
                routes = parser.parse(jObject);
            } catch (Exception e){
                e.printStackTrace();
            }
            return routes;
        }


        @Override
        protected void onPostExecute(List<List<HashMap<String, String>>> result) {
            ArrayList points = new ArrayList();


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

                List<HashMap<String, String>> path = result.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);
                }



            }

            // Drawing polyline in the Google Map
            mMap.getUiSettings().setZoomControlsEnabled(true);

            if (points.size() > 0) {
                PolylineOptions opts = new PolylineOptions().add(origin.getPosition(), destination.getPosition()).color(Color.BLUE).width(5);
                mMap.addPolyline(opts);
            }

        }
    }



    private String getDirectionsUrl(LatLng origin, LatLng dest){
        //origin fo route
        String str_origin  = "origin=" + origin.latitude + "," + origin.longitude;

        //destination of route
        String str_dest = "destination=" + dest.latitude + "," + dest.longitude;

        //Setting mode
        String mode = "mode=driving";

        //Building the parameters to the web service
        String parametrs = str_origin + "&" + str_dest + "&" + mode;

        //Output format
        String output = "json";

        //Building the url to the web service
        String url = "https://maps.googleapis.com/maps/api/directions/" + output + "?" +parametrs + "&key=" + "AIzaSyD_L8g3AcwXBKnEjhvLJwBXwI3L51LjQUU";

        return url;

    }

    /**
     *  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);
            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;
    }

}