获取 Google 地图中多段线的长度

Question

我的主要目标是获取两点之间的距离。我正在尝试计算多段线 start/end 之间的距离（以英里为单位）。使用下面的代码，我能够绘制折线。但是，我不知道如何获得这条折线的总距离。

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;
}

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("trDraw", e.toString());
    }finally{
        iStream.close();
        urlConnection.disconnect();
    }
    return data;
}

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);
    }
}

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);

            double lat;
            double lng;
            LatLng position = null;

            // Fetching all the points in i-th route
            for(int j=0;j<path.size();j++){
                HashMap<String,String> point = path.get(j);

                 lat = Double.parseDouble(point.get("lat"));
                 lng = Double.parseDouble(point.get("lng"));
                 position = new LatLng(lat, lng);

                points.add(position);
            }

            // Adding all the points in the route to LineOptions
            lineOptions.addAll(points);
            lineOptions.width(5);
            lineOptions.color(Color.RED);
            if(position == null){
                Toast.makeText(getApplicationContext(), "Something went wrong", Toast.LENGTH_LONG).show();
            }
            else{
             // Double totalDistance =  PolyUtil.distanceToLine(position ,driverStartLL, drivarDestinationLL);
               // Log.i("trTotalCost", "polyDistance: " + totalDistance);
            }

        }

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

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;
    }


}

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;
}

因为我试图用多段线计算两点的距离，所以使用 distanceOf(Location1, Location2); 函数会给我最短的可能距离对我来说毫无用处。由于我使用的是折线，所以该方法根本行不通。

谢谢。

Answer 1

@grant，所以 .forEach 会帮助你 :)

Answer 2

            JSONArray array = jObject.getJSONArray("routes");
            JSONObject routes = array.getJSONObject(0);
            JSONArray legs = routes.getJSONArray("legs");
            JSONObject steps = legs.getJSONObject(0);
            JSONObject distance = steps.getJSONObject("distance");

            Log.i("trJSON", "Distance String: " + distanceD.toString());
            Double dist = Double.parseDouble(distanceD.getString("text").replaceAll("[^\.0123456789]","") );
            Log.i("trJSON", "Distance Double: " + dist);

通过使用 legs.getJSONObject(0)，我可以从 steps 获得距离或持续时间。因此，在获得以英里为单位的距离字符串后，我只需将其转换为 Double.

获取 Google 地图中多段线的长度

Get Length of PolyLine in Google Maps

java

android

google-maps

polyline