Android使用localhost

Question

我有以下网址

mvc.local/users/login

为此，我有以下Android代码：

public String sendToServer(List<NameValuePair> pair, String url){
    HttpClient httpclient = new DefaultHttpClient();
    HttpPost httppost = new HttpPost(url);
    try {
        httppost.setEntity(new UrlEncodedFormEntity(pair));
        HttpResponse response = httpclient.execute(httppost);
        if (response != null) {
            InputStream ips  = response.getEntity().getContent();
            BufferedReader buf = new BufferedReader(new InputStreamReader(ips,"UTF-8"));
            if(response.getStatusLine().getStatusCode()!=HttpStatus.SC_OK)
            {
                try {
                    throw new Exception(response.getStatusLine().getReasonPhrase());
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
            StringBuilder sb = new StringBuilder();
            String s;
            while(true)
            {
                s = buf.readLine();
                if(s==null || s.length()==0)
                    break;
                sb.append(s);

            }
            buf.close();
            ips.close();
            return sb.toString();
        }

    } catch (UnsupportedEncodingException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (ClientProtocolException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    return "Error";
}

但是我收到以下错误：

 Caused by: java.lang.IllegalStateException: Target host must not be null, or set in parameters. scheme=null, host=null, path=

所以我的问题是如何使用localhost？