如何在Android的Google地图上绘制两个以上的路线？

Question

I want to display multiple points on a Google map with a route. The points should be dynamic, with input given by the user.

The output will look like as given below image :

I want to show the driving route between multiple locations in my Android app.

There are several answers on Stack Overflow itself, and all of them were using the same method. Get the directions from start point to destination using Google directions API, and draw a polyline across the points returned.

I used the below code but it shows the route between only two points. However, I want to display the route between multiple points.

Thanks in advance.

private GoogleMap mMap;
ArrayList<LatLng> markerPoints;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_maps);
    markerPoints = new ArrayList<LatLng>();

    SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.map);
    mapFragment.getMapAsync(this);
    Button btnDraw = (Button) findViewById(R.id.btn_draw);
    if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
        return;
    }
    mMap.setMyLocationEnabled(true);

    mMap.setOnMapClickListener(new GoogleMap.OnMapClickListener() {
        @Override
        public void onMapClick(LatLng point) {
            if (markerPoints.size() >= 10) {
                return;
            }

            markerPoints.add(point);
            MarkerOptions options = new MarkerOptions();
            options.position(point);

            if (markerPoints.size() == 1) {
                options.icon(BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_GREEN));
            } else if (markerPoints.size() == 2) {
                options.icon(BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_RED));
            } else {
                options.icon(BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_AZURE));
            }
            mMap.addMarker(options);
        }
    });

    mMap.setOnMapLongClickListener(new GoogleMap.OnMapLongClickListener() {
        @Override
        public void onMapLongClick(LatLng point) {
            mMap.clear();
            markerPoints.clear();

        }
    });

    btnDraw.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            if (markerPoints.size() >= 2) {
                LatLng origin = markerPoints.get(0);
                LatLng dest = markerPoints.get(1);
                String url = getDirectionsUrl(origin, dest);
                DownloadTask downloadTask = new DownloadTask();
                downloadTask.execute(url);
            }
        }
    });
}

private String getDirectionsUrl(LatLng origin, LatLng dest) {
    String str_origin = "origin=" + origin.latitude + "," + origin.longitude;
    String str_dest = "destination=" + dest.latitude + "," + dest.longitude;
    String sensor = "sensor=false";
    String waypoints = "";
    for (int i = 2; i < markerPoints.size(); i++) {
        LatLng point = (LatLng) markerPoints.get(i);
        if (i == 2)
            waypoints = "waypoints=";
        waypoints += point.latitude + "," + point.longitude + "|";
    }

    String parameters = str_origin + "&" + str_dest + "&" + sensor + "&" + waypoints;

    String output = "json";
    String url = "https://maps.googleapis.com/maps/api/directions/" + output + "?" + parameters;
    return url;
}

@SuppressLint("LongLogTag")
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 while downloading url", e.toString());
    } finally {
        iStream.close();
        urlConnection.disconnect();
    }
    return data;
}

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);
    }
}

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

    @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();

            routes = parser.parse(jObject);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return routes;
    }

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

        ArrayList<LatLng> points = null;
        PolylineOptions lineOptions = null;

        for (int i = 0; i < result.size(); i++) {
            points = new ArrayList<LatLng>();
            lineOptions = new PolylineOptions();

            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);
            }

            lineOptions.addAll(points);
            lineOptions.width(12);
            lineOptions.color(Color.RED);
        }

        // Drawing polyline in the Google Map for the i-th route
        mMap.addPolyline(lineOptions);
    }
}

@Override
public void onMapReady(GoogleMap googleMap) {
    mMap = googleMap;

    LatLng AT = new LatLng(20.039413, 74.479977);
    mMap.addMarker(new MarkerOptions().position(AT).title("Marker in Yeola"));
    mMap.moveCamera(CameraUpdateFactory.newLatLng(AT));
}

Answer 1

In your onPostExecute in the ParserTask there is an error which is easily corrected. In the outer loop, on result.size(), you recreate the lineOptions variable which means only the very last iteration will get added to the map since your addPolyline call is outside the loop.

So you can fix this in two ways but the result is the same:

• (a) Add all points to one array and then add to one lineOptions or
• (b) Add points from one iteration of path loop to one lineOptions and issue addPolyline for each iteration. (This seems like your intention.)

Since the map doesn't care how the aggregate path is comprised, and since the directions result will be properly terminated for each segment, I prefer (a) as the solution but I listed both.

To fix with option (a):

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

    ArrayList<LatLng> points = new ArrayList<>();
    PolylineOptions lineOptions = new PolylineOptions();

    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);
        }

    }

    lineOptions.addAll(points);
    lineOptions.width(12);
    lineOptions.color(Color.RED);

    // Drawing polyline in the Google Map for the entire route
    mMap.addPolyline(lineOptions);
}

To fix with option (b):

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

    ArrayList<LatLng> points = new ArrayList<>();

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

        points.clear();
        PolylineOptions lineOptions = new PolylineOptions();

        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);
        }

        lineOptions.addAll(points);
        lineOptions.width(12);
        lineOptions.color(Color.RED);

        // Drawing polyline in the Google Map for the i-th route
        mMap.addPolyline(lineOptions);


    }