從谷歌方向解析JSON API

Question

我想從谷歌地圖上的起點到終點一步一步地解析方向。解析我使用下面的鏈接：

Google Map Direction API

該鏈接我想分析「機動」 JSON數組。

我該如何從該json文件中獲得一步一步的指示，並且應該在哪裏更改爲我的代碼？ thanx提前......從此我的代碼 與衆不同的是屏幕下方的：

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; 
    } 
} 

Answer 1

首先，你必須瞭解有關JSONArray & JSONObject，你可以按照android-json-parsing-tutorial的JSON解析。

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 = ((JSONArray)jRoutes.get(i)).getJSONArray("legs"); 
      List path = new ArrayList<HashMap<String, String>>(); 

      /** Traversing all legs */ 
      for(int j=0;j<jLegs.length();j++){ 
       jSteps = ((JSONArray)jLegs.get(j)).getJSONArray("steps"); 

       /** Traversing all steps */ 
       for(int k=0;k<jSteps.length();k++){ 

        String html_instructions = jSteps.get(k).getString("html_instructions"); 
        String travel_mode = jSteps.get(k).getString("travel_mode"); 
        String maneuver = jSteps.get(k).getString("maneuver"); 

        String distance_text = jSteps.get(k).getJSONObject("distance").getString("text"); 
        String distance_value = jSteps.get(k).getJSONObject("distance").getString("value"); 

        String duration_text = jSteps.get(k).getJSONObject("duration").getString("text"); 
        String duration_value = jSteps.get(k).getJSONObject("duration").getString("value"); 

        String start_lat = jSteps.get(k).getJSONObject("start_location").getString("lat"); 
        String start_lon = jSteps.get(k).getJSONObject("start_location").getString("lng"); 

        String end_lat = jSteps.get(k).getJSONObject("end_location").getString("lat"); 
        String end_lon = jSteps.get(k).getJSONObject("end_location").getString("lng"); 

        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; 
}