Android：带参数的 Http post 不起作用

我需要创建一个带有参数的 HTTP POST 请求。我知道有很多例子，我尝试过使用 HTTPparams、NameValuePair 等，但似乎无法获得服务器的正确格式。

Server Type: REST based API utilizing JSON for data transfer
Content-type: application/json
Accept: application/json
Content-length: 47
{"username":"abcd","password":"1234"}

我可以传递这些标头，但我似乎无法传递这些参数“用户名”、“密码”。这是我的代码：

    HttpClient client = new DefaultHttpClient();  
    HttpPost post = new HttpPost("http://www.mymi5.net/API/auth/login");   
    List<NameValuePair> pairs = new ArrayList<NameValuePair>();  
    pairs.add(new BasicNameValuePair("username","abcd"));  
    pairs.add(new BasicNameValuePair("password","1234"));  
    post.setHeader("Content-type", "application/json");
    post.setHeader("Accept", "application/json");
    UrlEncodedFormEntity entity = new UrlEncodedFormEntity(pairs,"UTF-8");  
    post.setEntity(entity);  
    HttpResponse response = client.execute(post);  

我尝试调试，但无法查看实体是否正确附加...我做错了什么？

提前致谢。 马兹

尝试这个：

HttpClient client = new DefaultHttpClient();  
    HttpPost post = new HttpPost("http://www.mymi5.net/API/auth/login");   
    post.setHeader("Content-type", "application/json");
    post.setHeader("Accept", "application/json");
JSONObject obj = new JSONObject();
obj.put("username", "abcd");
obj.put("password", "1234");
    post.setEntity(new StringEntity(obj.toString(), "UTF-8"));
    HttpResponse response = client.execute(post);