nullpointerexception当从谷歌地点api请求xml附近的地方

Question

我正在做一个应用程序，请求某个类型的最近的地方，并返回列表中的每个结果的名称，坐标和信息，我使用谷歌地方的api为此。

我的代码如下

Helper.java具有一个发送网址传送至Google服务器的方法和检索一个XML文件，并将其解析到包含名称，坐标和信息对象的列表：

public Document getDocument(int radius, String type, LatLng current) { 

     String url = "https://maps.googleapis.com/maps/api/place/nearbysearch/xml?" 
       + "location=" 
       + current.latitude 
       + "," 
       + current.longitude 
       + "&radius=" 
       + radius 
       + "&types=" 
       + type 
       + "&sensor=true&key=MyKeyHere"; //i replace this with my api key 

     Log.d("URL", url); 

     try { 

      HttpClient httpClient = new DefaultHttpClient(); 
      HttpContext localContext = new BasicHttpContext(); 
      HttpPost httpPost = new HttpPost(url); 
      HttpResponse response = httpClient.execute(httpPost, localContext); 
      InputStream in = response.getEntity().getContent(); 
      DocumentBuilder builder = DocumentBuilderFactory.newInstance() 
        .newDocumentBuilder(); 
      Document doc = builder.parse(in); 
      Log.d("Document content", doc.getTextContent()); 
      return doc; 
     } catch (Exception e) { 
      e.printStackTrace(); 
     } 
     return null; 
    } 

    public ArrayList<MyLocation> getNearbyLocations(Document doc) { 
     Log.d("DOC**", doc.getTextContent()); 

     ArrayList<MyLocation> nearbyLocations = new ArrayList<MyLocation>(); 
     String name; 
     double lati; 
     double longi; 
     String info; 
     // MyLocation theLocation; 

     NodeList nLName = doc.getElementsByTagName("name"); 
     NodeList nLLat = doc.getElementsByTagName("lat"); 
     NodeList nLLong = doc.getElementsByTagName("lng"); 
     NodeList nLvicinity = doc.getElementsByTagName("vicinity"); 
     for (int i = 0; i < nLName.getLength(); i++) { 

      name = nLName.item(i).getNodeValue(); 
      lati = Double.parseDouble(nLLat.item(i).getNodeValue()); 
      longi = Double.parseDouble(nLLong.item(i).getNodeValue()); 
      info = nLvicinity.item(i).getNodeValue(); 
      nearbyLocations.add(new MyLocation(name, new LatLng(lati, longi), 
        info)); 
      Log.d("LIST***", nearbyLocations.toString()); 
     } 

     return nearbyLocations; 
    } 

Search.java

protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_search); 




     Helper= new Helper(); 


     LocationManager locManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE); 
     locManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 1000, 1, ls); 

     Location location = locManager.getLastKnownLocation(LocationManager.GPS_PROVIDER); 
     ls.onLocationChanged(location); 

    docu = Helper.getDocument(5000, "airport" ,new LatLng(alti, longi)); 
     nearByLocation= Helper.getNearbyLocations(docu); ////it gives me a nullpointerexception here 

     //Log.d("DOC***", docu.getTextContent()); 

     listView = (ListView) findViewById(R.id.my_list2); 
     adapter = new ItemAdapter(this, getItems()); 
     listView.setAdapter(adapter); 

    } 

第

问题是程序在调用方法getNearByLocations（doc）时崩溃，我认为问题是检索到的文档总是空的，所以我不知道我检索XML文件的方法是否是错误的。

这里是我的logcat：

10-04 19:40:43.049: E/AndroidRuntime(1737): Caused by: java.lang.NullPointerException 
10-04 19:40:43.049: E/AndroidRuntime(1737):  at com.Gourp_KSA.tourfit.Helper.getNearbyLocations(Helper.java:95) 
10-04 19:40:43.049: E/AndroidRuntime(1737):  at com.Gourp_KSA.tourfit.Search.onCreate(Search.java:85) 
10-04 19:40:43.049: E/AndroidRuntime(1737):  at android.app.Activity.performCreate(Activity.java:5104) 
10-04 19:40:43.049: E/AndroidRuntime(1737):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080) 
10-04 19:40:43.049: E/AndroidRuntime(1737):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144) 

编辑&答：
所以，我发现了什么问题。这是我在主线程上建立网络连接。我做了一个AsyncTask类来调用getNearbyLocations（）方法。我希望这可以帮助

Answer 1

当我相信您应该向Google Places API发送HTTP GET请求时，看起来您正在使用HTTP POST请求。

如果您有兴趣使用能够为您完成所有这些工作的Java库，并允许您通过Java方法和对象与Google Places API进行交互，则可以尝试Sprockets（披露：我是开发人员）。

等效链轮电话的方式获得Place的List对象将是：

Places.nearbySearch(Params.create().latitude(lat).longitude(lng) 
     .radius(5000).types("airport")).getResult();