JSON解析Android中的NullPointerException異常

Question

我正在學習Android中的JSON解析。我的logcat顯示NullPointerException onpostexecute方法。我已經分享了下面的代碼。在主要活動

JSONParser jParser = (JSONParser) new JSONParser().execute(url); 
    try 
    { 
     Thread.sleep(2000); 

    } 
    catch (InterruptedException e) 
    { 
     // TODO: handle exception 
     e.printStackTrace(); 
    } 

    // getting JSON string from URL 
    JSONObject json = jParser.getJSONFromUrl(); 

protected String doInBackground(String... urls) 
{ 

    // TODO Auto-generated method stub 
    try { 
     // defaultHttpClient 
     DefaultHttpClient httpClient = new DefaultHttpClient(); 
     HttpPost httpPost = new HttpPost(url1); 

     HttpResponse httpResponse = httpClient.execute(httpPost); 
     HttpEntity httpEntity = httpResponse.getEntity(); 
     is = httpEntity.getContent();   

    } catch (UnsupportedEncodingException e) { 
     e.printStackTrace(); 
    } catch (ClientProtocolException e) { 
     e.printStackTrace(); 
    } catch (IOException e) { 
     e.printStackTrace(); 
    } 

    try { 
     BufferedReader reader = new BufferedReader(new InputStreamReader(
       is, "iso-8859-1"), 8); 
     StringBuilder sb = new StringBuilder(); 
     String line = null; 
     while ((line = reader.readLine()) != null) { 
      sb.append(line + "\n"); 
     } 
     is.close(); 
     result = sb.toString(); 
    } catch (Exception e) { 
     Log.e("Buffer Error", "Error converting result " + e.toString()); 
    } 

    return result; 

} 
protected void onPostExecute(String result) { 
     // try parse the string to a JSON object 
     try { 
      jObj = new JSONObject(result); 
     } catch (JSONException e) { 
      Log.e("JSON Parser", "Error parsing data " + e.toString()); 
     } 

    } 
     public JSONObject getJSONFromUrl() 
    { 
    return jObj; 
    } 

JSONParser對象我想不通的問題。提供建議....

Answer 1

總是你必須添加空檢查後得到服務器的響應。