Google 方向 API 不显示多条路径

Question

我想显示从源到目的地的多条路径，我在我的 URL 中使用参数 "alternatives=true" 作为方向 API。但是我无法显示一条以上的路线。我想我的 onPostExecute() 方法的显示部分有问题。请解决我的问题。

public void MapPoints(double SourceOne, double DestinationOne, double SourceTwo, double DestinationTwo){




        //LatLng origin = points.get(0);
        //LatLng dest = points.get(1);
        double SourceOneDraw = SourceOne;
        double DestinationOneDraw = DestinationOne;
        double SourceTwoDraw = SourceTwo;
        double DestinationTwoDraw = DestinationTwo;



        LatLng origin = new LatLng(SourceOneDraw,DestinationOneDraw);
        LatLng dest =  new LatLng(SourceTwoDraw,DestinationTwoDraw);

        // 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";

        //Adding Alternative parameter
        String alternative = "alternatives=true";

        // Building the parameters to the web service
        String parameters = str_origin+"&"+str_dest+"&"+sensor+"&"+alternative;

        // 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());
            Toast.makeText(getApplicationContext(),"Error",Toast.LENGTH_LONG).show();
        }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(5);
                lineOptions.color(Color.RED);
            }

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

Answer 1

查看您的代码，我相信我明白了问题所在。您有一个 for 循环，在其中循环遍历结果：

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

但是，绘制折线的代码行不在此循环内：

mMap.addPolyline(lineOptions);

如果我错了请纠正我，但看起来上面的行只会执行一次，因为它不在循环中。这将导致在地图上只绘制一条路径。如果您尝试将这行代码移动到 for 循环内，您会在地图上看到多条路径吗？整个函数如下所示：

@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(5);
            lineOptions.color(Color.RED);

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


    }

Google 方向 API 不显示多条路径

Google Direction API not displaying multiple paths

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google-directions-api