我试图使用谷歌地图绘制两个标记点之间的路径。但它没有显示出任何道路

Question

您好我是Android的新手。我从stackoverflow中获取了一个代码，以便在谷歌地图上的两个标记点之间建立路径。但是在跑步之后我没有得到这条路。请帮忙。 我在这里使用了Google map api密钥。

我的网址是。

public String makeURL (double sourcelat, double sourcelog, double destlat, double destlog ){
    StringBuilder urlString = new StringBuilder();
    urlString.append("http://maps.googleapis.com/maps/api/directions/json");
    urlString.append("?origin=");// from
    urlString.append(Double.toString(sourcelat));
    urlString.append(",");
    urlString
            .append(Double.toString( sourcelog));
    urlString.append("&destination=");// to
    urlString
            .append(Double.toString( destlat));
    urlString.append(",");
    urlString.append(Double.toString( destlog));
    urlString.append("&sensor=false&mode=walking&alternatives=true");
    urlString.append("&key=Google_Map_Key");

    return urlString.toString();
}

这是我的绘制函数，它从JSON中获取数据。

public void drawPath（String result）{

    try {
        //Tranform the string into a json object
        JSONObject json = new JSONObject(result);
        JSONArray routeArray = json.getJSONArray("routes");
        JSONObject routes = routeArray.getJSONObject(0);
        JSONObject overviewPolylines = routes.getJSONObject("overview_polyline");
        String encodedString = overviewPolylines.getString("points");
        List<LatLng> list = decodePoly(encodedString);
       /* Polyline line = mMap.addPolyline(new PolylineOptions()
                //.addAll(list)
                .add(list.get(0))
                .add(list.get(1))
                .width(5)
                .color(Color.parseColor("#05b1fb"))//Google maps blue color
                .geodesic(true)
                .visible(true)
        );*/

        /*line.isVisible();*/

       for(int z = 0; z<list.size()-1;z++){
            LatLng src= list.get(z);
            LatLng dest= list.get(z+1);
            Polyline line = mMap.addPolyline(new PolylineOptions()
            .add(new LatLng(src.latitude, src.longitude), new LatLng(dest.latitude,   dest.longitude))
            .width(2)
            .color(Color.BLUE).geodesic(true));
        }

    }
    catch (JSONException e) {

    }
}

我的JSONPArser类是

公共类JSONParser {

//static InputStream is = null;
static JSONObject jObj = null;
static String json = "";
// constructor
//public JSONParser() {
//}
public JSONParser() {

}

public String getJSONFromUrl(String url) {

    try{
        URL Url = new URL(url);//use a proper url instead of onlineUrl
        HttpURLConnection connection = (HttpURLConnection) Url.openConnection();
        //connection.setRequestProperty("User-Agent", "");
        //connection.setRequestMethod("GET");//we can use POST instead of GET method also.
        //connection.setDoInput(true);
        connection.connect();

        //URL url = new URL(strUrl);

        // Creating an http connection to communicate with url
        // urlConnection = (HttpURLConnection) url.openConnection();

        // Connecting to url
        //urlConnection.connect();
        InputStream inputStream = connection.getInputStream();
        if (inputStream != null) {
            BufferedReader reader = new BufferedReader(new InputStreamReader(
                    inputStream, "iso-8859-1"), 8);
            StringBuilder sb = new StringBuilder();
            String line = null;
            while ((line = reader.readLine()) != null) {
                sb.append(line + "\n");
            }

            json = sb.toString();
            inputStream.close();
            //Log.i(TAG, "The result: " + result.toString());
            //return this result
        }

    } catch (IOException e) {
        // writing exception to log
        e.printStackTrace();
    }

    return json;

}

}