简单地说有下面三种：
第一种： java.net. (标准java接口)----HttpURLConnection
try{
URL url = new URL("http://www.baidu.com")//定义地址
HttpURLConnection http = (HttpURLConnection) url.openConnection();//打开连接
int nRC = http.getResponseCode();//得到连接状态
if(nRC == HttpURLConnection.HTTP_OK){
InputStream is = http.getInputStream();//取得数据
.....//处理数据
}
}catch(Exception e){
//因是连接网络，不免会出现一些异常，所以必须处理这些异常
}
第二种 Apache接口---HttpClient
try{
HttpClient hc = new DefaultHttpClient();//创建HttpClient,这里使用DefaultHttpClient表示默认属性
HttpGet hg = new HttpGet("http://www.baidu.com");//HttpGet实例
HttpResponse rp = hc.execute(hg);//连接
if(rp.getStatusLine().getStatusCode() == HttpStatus.SC_OK){
InputStream is = rp.getEntity().getContent();
.....//处理数据
}
}catch(IOEeception e){
}
第三种 套接字 Socket网络接口
try{
InetAddress ia = InetAddress.getByName("192.168.1.110");//IP地址
Socket sk = new Socket(ia,61203,true);//端口
InputStream is =sk.getInputStream();//得到数据
OutputStream os = sk.getOutputStream();
.....//数据处理
os.close();
is.close();
sk.close();
}catch(UnknownHostException e){
}catch(IOException e){
}
另外还有种： Android.net网络接口
android自带的接口，常常使用此包下的类进行Android特有的网络编程，如：访问WiFi，访问Android联网信息，邮件等功能。
private Context mContext;
AndroidNet(Context context) {
this.mContext = context;
}
/**
* 确定您是否连入了互联网
* 如果您未连入互联网，则无需安排基于互联网资源的更新。 下面这段代码展示了如何利用 ConnectivityManager 查询活动网络并确定其是否连入了互联网。
* @return true 已连接
*/
private boolean IsNoConnected( ) {
ConnectivityManager cm =
(ConnectivityManager) mContext.getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo activeNetwork = cm.getActiveNetworkInfo();
boolean isConnected = activeNetwork != null && activeNetwork.isConnectedOrConnecting();
//是否是wifi
//boolean isWiFi = activeNetwork.getType() == ConnectivityManager.TYPE_WIFI;
return isConnected;
}
这个在https://developer.android.google.cn/reference/android/net/wifi/package-summary有讲。
这里详细介绍一下 HttpURLConnection接口---Google官方推荐
HttpURLConnection的压缩和缓存机制可以有效地减少网络访问的流量，提升速度和省电。
HttpURLConnection默认使用Get请求：
public void sendRequest(String url) throws IOException {
String line = null;.
String result = null;
//使用HttpURLConnection 打开链接
try{
Url mUrl = new Url(url);
HttpURLConnection mHttpURLConnection = (HttpURLConnection ) mUrl.openConnection();
//读取响应的内容(流)
InputStreamReader mInputStreamReader = new InputStreamReader(new InputStream(mHttpURLConnection.getInputStream()));
BufferedReader mBufferedReader = new BufferedReader(mInputStreamReader );
if ((line = mBufferedReader.readLine())) {
result = line + “\n”;
}
Log.e("", "请求结果：" + result);
} catch ((MalformedURLException e)
{
Log.e(DEBUG_TAG, "MalformedURLException");
} finally {
mInputStreamReader.close();
mHttpURLConnection.disconnect();
}
}
HttpURLConnection的Post请求:
public void sendRequest(String url) throws IOException {
String line = null;.
String result = null;
try{
Url mUrl = new Url(url);
HttpURLConnection mHttpURLConnection = (HttpURLConnection ) mUrl.openConnection();
//设置读取超时为10秒
mHttpURLConnection.setReadTimeout(10000);
//设置链接超时为15秒
mHttpURLConnection.setConnectionTimeout(15000);
//设置请求方式
mHttpURLConnection.setRequestMethod("Post");
//接收输入流
mHttpURLConnection.setDoInput(true);
//启动输出流，当需要传递参数时需要开启
mHttpURLConnection.setDoOutput(true);
//添加Header
mHttpURLConnection.setRequestProperty("Connection", "Keep-Alive");
//添加请求参数
List<NameValuePair> paramsList = new ArrayList<NameValuePair>();
paramsList .add(new BasicNameValuePair("username", "myname"));
paramsList .add(new BasicNameValuePair("password", "mypwd"));
//将参数写入到输出流
wriParams(mHttpURLConnection.getOutputStream(), paramsList);
//发起请求
mHttpURLConnection.connect();
BufferedReader mBufferedReader = new BufferedReader(new InputStreamReader(mHttpURLConnection.getInputStream()));
StringBuilder sb = new StringBuilder();
while((line = mBufferedReader.readLine()) != null) {
sb.append(line + "\n");
}
result = sb.toString();
} catch ((MalformedURLException e)
{
Log.e(DEBUG_TAG, "MalformedURLException");
} finally {
mHttpURLConnection.disconnect();
}
}
private void writeParams(OutputStream mOutputStream, List<NameValuePair> paramsList){
StringBuilder paramStr = new StringBuilder();
for (NameValuePair pair : paramsList) {
if (!TextUtils.isEmpty(paramStr)) {
paramStr.append("&"):
}
paramStr.append(URLEncoder.encode(pair.getName(), "UTF-8"));
paramStr.append("=");
paramStr.append(URLEncoder.encode(pair.getValue(), "UTF-8"));
}
BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(mOutputStream, "UTF-8"));
//将参数写入输出流
writer.write(paramStr.toString());
writer.flush();
writer.close();
}
注：任何输出流都是有缓冲区的,Bufferedxxx这种输出流提供可配置缓冲区大小，其他输出流都是有默认大小的缓冲区的,FileWriter的flush()方法是从OutputStreamWriter中继承来的,其作用就是 清空缓冲区并完成文件写入操作的。
