如何从 JSON 文件中获取 lng 和 lat

Question

我想从我的 JSON 文件中获取“lat”和“lng”并添加到一个保存 GeoPoint 的数组中。我试图这样做，但它对我不起作用：

protected List<GeoPoint> JsonArray(){
        List<GeoPoint> endp = new ArrayList<GeoPoint>();

        try{
        JSONObject obj = new JSONObject(json);
        JSONArray steps = obj.getJSONArray("routes");
        for(int i=0;i<steps.length();i++){
            JSONObject temp = steps.getJSONObject(i);
            JSONObject ele = temp.optJSONObject("steps").optJSONObject("end_location");
            ele.getJSONObject("lat");
            ele.getJSONObject("lng");

            double lat = Double.parseDouble(ele.getJSONObject("lat").toString());
            double lng = Double.parseDouble(ele.getJSONObject("lng").toString());
            endp.add(new GeoPoint((int)(lat *1E6),(int)(lng * 1E6)));

        }



        }catch (JSONException e) {
            // TODO: handle exception
        }
        return endp;
    }

这是我的 JSON 文件的一部分外观：

{
       "routes" : [
          {
             "bounds" : {
                "northeast" : {
                   "lat" : 41.87999000000001,
                   "lng" : -87.615020
                },
                "southwest" : {
                   "lat" : 29.74674000000001,
                   "lng" : -95.361220
                }
             },
             "copyrights" : "Dane do Mapy ©2013 Google",
             "legs" : [
                {
                   "distance" : {
                      "text" : "1 085 mil",
                      "value" : 1746457
                   },
                   "duration" : {
                      "text" : "16 godz. 39 min",
                      "value" : 59955
                   },
                   "end_address" : "1362 Chenevert Street, Houston, Teksas 77003, Stany Zjednoczone",
                   "end_location" : {
                      "lat" : 29.750110,
                      "lng" : -95.36016000000001
                   },
                   "start_address" : "138-230 South Columbus Drive, Chicago, Illinois 60601, Stany Zjednoczone",
                   "start_location" : {
                      "lat" : 41.87999000000001,
                      "lng" : -87.62075000000002
                   },
                   "steps" : [
                      {
                         "distance" : {
                            "text" : "338 stóp",
                            "value" : 103
                         },
                         "duration" : {
                            "text" : "1 min",
                            "value" : 9
                         },
                         "end_location" : {
                            "lat" : 41.88090,
                            "lng" : -87.62069000000001
                         },
                         "html_instructions" : "Kieruj się \u003cb\u003eS Columbus Dr\u003c/b\u003e na \u003cb\u003epółnoc\u003c/b\u003e w stronę \u003cb\u003eE Monroe St\u003c/b\u003e",
                         "polyline" : {
                            "points" : "}tr~FtlxuOuA@w@@QMUA"
                         },
                         "start_location" : {
                            "lat" : 41.87999000000001,
                            "lng" : -87.62075000000002
                         },
                         "travel_mode" : "DRIVING"
                      },
                      {
                         "distance" : {
                            "text" : "0,2 mil",
                            "value" : 266
                         },
                         "duration" : {
                            "text" : "1 min",
                            "value" : 33
                         },
                         "end_location" : {
                            "lat" : 41.88086000000001,
                            "lng" : -87.61750000000001
                         },
                         "html_instructions" : "Skręć \u003cb\u003ew prawo\u003c/b\u003e w \u003cb\u003eE Monroe St\u003c/b\u003e",
                         "polyline" : {
                            "points" : "szr~FhlxuO?SAyA?_B@yA?iBAaB?WBE@C@A?C?A@A?C?y@?_@"
                         },
                         "start_location" : {
                            "lat" : 41.88090,
                            "lng" : -87.62069000000001
                         },
                         "travel_mode" : "DRIVING"
                      },
                      {
                         "distance" : {
                            "text" : "2,0 mil",
                            "value" : 3186
                         },
                         "duration" : {
                            "text" : "3 min",
                            "value" : 180
                         },
                         "end_location" : {
                            "lat" : 41.85320,
                            "lng" : -87.61470000000001
                         },
                         "html_instructions" : "Skręć \u003cb\u003ew prawo\u003c/b\u003e w \u003cb\u003eU.S. 41 S\u003c/b\u003e",
                         "polyline" : {
                            "points" : "kzr~FjxwuOpMOZ@`PO|ACvDC@?lDCZAfMGjAA`@Av@?^?P?N@P@j@LRFNDRJRHZRb@\\b@^nAjA@@JJXXb@b@z@v@RRp@`@RLr@Xn@Np@J`A@bBOp@Kv@K@?@?@A@?@?@?@?PEvBWxB]fDq@xA]jF_BTIj@QpGuBd@OBAf@SrDyAPGNG@AVKbA_@~@]|@]z@Y`F{AtCy@fHyB"
                         },
                         "start_location" : {
                            "lat" : 41.88086000000001,
                            "lng" : -87.61750000000001
                         },
                         "travel_mode" : "DRIVING"
                      },
                      {
                         "distance" : {
                            "text" : "0,4 mil",
                            "value" : 581
                         },
                         "duration" : {
                            "text" : "1 min",
                            "value" : 30
                         },
                         "end_location" : {
                            "lat" : 41.848390,
                            "lng" : -87.614670
                         },
                         "html_instructions" : "Zjedź \u003cb\u003eInterstate 55 S\u003c/b\u003e w kierunku \u003cb\u003eSaint Louis\u003c/b\u003e",
                         "polyline" : {
                            "points" : "omm~FzfwuOVDPAN?VGlBk@b@M@?JEDAVI`A[dBi@`A[z@UPGZGf@E\\Ab@@VDJBHBTFTHRJPNRNLL\\f@NXLTP\\BF"
                         },
                         "start_location" : {
                            "lat" : 41.85320,
                            "lng" : -87.61470000000001
                         },
                         "travel_mode" : "DRIVING"
                      },

有谁知道我该怎么做？

Answer 1

您的变量 JSONArray steps = obj.getJSONArray("routes"); 不代表 JSON 对象的“步骤”部分，而是代表“路线”部分。

此外，您还跳过了 JSON 层次结构中的一些级别。使用给定的 JSON，您将需要以下步骤来遍历 JSON（我省略了对不同数组的循环，除了 routes 数组）

JSONArray routes = obj.getJSONArray("routes");
for(int i=0; i < routes.length(); i++){
    // Grab the first route
    JSONObject route = routesArray.getJSONObject(i);
    // Take all legs from the route
    JSONArray legs = route.getJSONArray("legs");
    // Grab first leg
    JSONObject leg = legs.getJSONObject(0);
    // Take all steps from the leg
    JSONArray steps = leg.getJSONArray("steps");
    // Grab first step
    JSONObject step = steps.getJSONObject(0);

    JSONObject endLocation = step.getJSONObject("end_location");
    String lat = endLocation.getString("lat");
    String lng = endLocation.getString("lng");

参考：JSON parsing of Google Maps API in Android App

Answer 2

解析当前的 json 字符串以获得 lat 和 lng :

JSONObject obj = new JSONObject(json);
        JSONArray steps = obj.getJSONArray("routes");
        for(int i=0;i<steps.length();i++){
            JSONObject temp = steps.getJSONObject(i);

             // get bounds JSONObject 
            JSONObject boundsjsonobj = temp.getJSONObject("bounds");
             // get northeast JSONObject
            JSONObject jsonboj_bounds_northeast= boundsjsonobj.getJSONObject("northeast");
            // get northeast lng and lat 
             String str_northeast_lat=jsonboj_bounds_northeast.getString("lat");
             String str_northeast_lng=jsonboj_bounds_northeast.getString("lng");
             // get southwest JSONObject
             JSONObject jsonboj_bounds_southwest= boundsjsonobj.getJSONObject("southwest");
            // get northeast lng and lat 
             String str_southwest_lat=jsonboj_bounds_southwest.getString("lat");
             String str_southwest_lng=jsonboj_bounds_southwest.getString("lng");

             //get legs JsonArray from routes
             JSONArray jsonarray_legs = temp.getJSONArray("legs");
             for(int j=0;j<jsonarray_legs.length();j++){
                JSONObject jobjlegs = jsonarray_legs.getJSONObject(j);
                 // get end_location json object

                 JSONObject jobjlegs_end_location = jobjlegs.getJSONObject("end_location");
                  String str_end_location_lat==jobjlegs_end_location.getString("lat");
                  String str_end_location_lng==jobjlegs_end_location.getString("lng");

                  // get start_address object


                 JSONObject jobjlegs_start_address = jobjlegs.getJSONObject("start_address");
                  String str_start_address_lat==jobjlegs_start_address.getString("lat");
                  String str_start_address_lng==jobjlegs_start_address.getString("lng");

                  // get steps jsonArray
                  JSONArray jsonarray_steps = jobjlegs.getJSONArray("steps");
                  for(int k=0;k<jsonarray_steps.length();k++){
                JSONObject jobjsteps = jsonarray_steps.getJSONObject(k);

                    // get end_location jsonobject
                     JSONObject jobjsteps_end_location = jobjsteps.getJSONObject("end_location");
                       double latend = Double.parseDouble(jobjsteps_end_location.getString("lat"));
                       double lngend = Double.parseDouble(jobjsteps_end_location.getString("lng"));
                       endp.add(new GeoPoint((int)(latend *1E6),(int)(lngend * 1E6)));

                     // get start_location jsonobject
                     JSONObject jobjsteps_start_location = jobjsteps.getJSONObject("start_location");
                       double latstart = Double.parseDouble(jobjsteps_start_location.getString("lat"));
                       double lngstart = Double.parseDouble(jobjsteps_start_location.getString("lng"));
                  }

             }

        }