android异步http总是onFailure（状态代码=0），但DefaultHttpClient没有问题

我正在尝试使用，但总是onFailure，从日志中可以看到状态代码=0。但是，当我使用传统方式（org.apache.http.client.HttpClient）时，状态代码=200

守则：

公共类HttpTestActivity扩展了ActionBarActivity{

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_http_test);

    testHttp();
    testHttp2();
}

public void testHttp2() {
    new Thread(new Runnable() {
        @Override
        public void run() {
            HttpClient httpClient = new DefaultHttpClient();
            HttpGet httpGet = new HttpGet("http://www.baidu.com");
            try {
                HttpResponse httpResponse = httpClient.execute(httpGet);
                int statusCode = httpResponse.getStatusLine().getStatusCode();
                Log.i("ws", "---->>22: status code: " + statusCode);
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }).start();
}

public void testHttp() {
    Log.i("ws", "---->>testHttp");
    VStarRestClient.get("http://www.baidu.com", null, new AsyncHttpResponseHandler() {

        @Override
        public void onSuccess(int statusCode, Header[] headers, byte[] responseBody) {
            Log.i("ws", "---->>onSuccess :" + statusCode);
        }

        @Override
        public void onFailure(int statusCode, Header[] headers, byte[] responseBody, Throwable error) {
            Log.i("ws", "---->>onFailure : " + statusCode);
        }
        });
}

如果得到的错误为0，则检查错误字段， 它显示了确切的问题，如java.net.SocketTimeoutException等

 @Override
    public void onFailure(int statusCode, Header[] headers, byte[] responseBody, Throwable error) {
        Log.i("ws", "---->>onFailure : " + error);
    }
    });