1、在android4中，发起网络http操作，不能在Activity的事件（即主线程）中进行，必须在单独的线程中操作。
另外进行网络操作，需要在manifest文件中增加如下的权限：
<uses-permission android:name="android.permission.INTERNET" />
2、下面给出代码事例
public void loadData() {new AsyncTask<String, Void, String>() {@Overrideprotected String doInBackground(String... paramsInput) {String url = "http://10.0.0.5:8080/examples/action";List<NameValuePair> params = new ArrayList<NameValuePair>();params.add(new BasicNameValuePair("type", paramsInput[0]));params.add(new BasicNameValuePair("id", paramsInput[1]));/* 建立HTTPPost对象 */HttpPost httpRequest = new HttpPost(url);String strResult = "doPostError";try {HttpClient httpClient = getHttpClient();/* 添加请求参数到请求对象 */httpRequest.setEntity(new UrlEncodedFormEntity(params,HTTP.UTF_8));/* 发送请求并等待响应 */HttpResponse httpResponse = httpClient.execute(httpRequest);/* 若状态码为200 ok */if (httpResponse.getStatusLine().getStatusCode() == 200) {/* 读返回数据 */strResult = EntityUtils.toString(httpResponse.getEntity());} else {strResult = "Error Response: "+ httpResponse.getStatusLine().toString();}} catch (ClientProtocolException e) {strResult = "Error Response: " + e.getMessage().toString();e.printStackTrace();} catch (IOException e) {strResult = "Error Response: " + e.getMessage().toString();e.printStackTrace();} catch (Exception e) {strResult = "Error Response: " + e.getMessage().toString();e.printStackTrace();}return strResult;}@Overrideprotected void onPostExecute(String result) {TextView view = (TextView) findViewById(R.id.resultText);view.setText(result);super.onPostExecute(result);}}.execute("query","1");}private HttpClient getHttpClient() {// 创建 HttpParams 以用来设置 HTTP 参数（这一部分不是必需的）HttpParams httpParams = new BasicHttpParams();// 设置连接超时和 Socket 超时，以及 Socket 缓存大小HttpConnectionParams.setConnectionTimeout(httpParams, 20 * 1000);HttpConnectionParams.setSoTimeout(httpParams, 20 * 1000);HttpConnectionParams.setSocketBufferSize(httpParams, 8192);// 设置重定向，缺省为 trueHttpClientParams.setRedirecting(httpParams, true);// 设置 user agentString userAgent = "Mozilla/5.0 (Windows; U; Windows NT 5.1; zh-CN; rv:1.9.2) Gecko/20100115 Firefox/3.6";HttpProtocolParams.setUserAgent(httpParams, userAgent);// 创建一个 HttpClient 实例// 注意 HttpClient httpClient = new HttpClient(); 是Commons HttpClient// 中的用法，在 Android 1.5 中我们需要使用 Apache 的缺省实现 DefaultHttpClientHttpClient httpClient = new DefaultHttpClient(httpParams);return httpClient;}
上述代码的loadData方法中，创建一个AsyncTask对象，在对象的doInBackground方法中发起网络操作，获取到操作结果。然后在onPostExecute方法中，利用前面获取到的结果更新界面。
这里的网络操作主要是利用了HttpClient等相关api，位于org.apache.http.client.HttpClient下。