Android网络编程
Android平台有三种网络接口可以使用，他们分别是：java.net.*(标准Java接口)、Org.apache接口和Android.net.*(Android网络接口)。下面分别介绍这些接口的功能和作用。
1.标准Java接口
java.net.*提供与联网有关的类，包括流、数据包套接字(socket)、Internet协议、常见Http处理等。比如：创建URL，以及URLConnection/HttpURLConnection对象、设置链接参数、链接到服务器、向服务器写数据、从服务器读取数据等通信。这些在Java网络编程中均有涉及，我们看一个简单的socket编程，实现服务器回发客户端信息。
服务端：
布局文件：
strings.xml
1.标准Java接口
java.net.*提供与联网有关的类，包括流、数据包套接字(socket)、Internet协议、常见Http处理等。比如：创建URL，以及URLConnection/HttpURLConnection对象、设置链接参数、链接到服务器、向服务器写数据、从服务器读取数据等通信。这些在Java网络编程中均有涉及，我们看一个简单的socket编程，实现服务器回发客户端信息。
服务端：
public class Server implements Runnable{
@Override
public void run() {
Socket socket = null;
try {
ServerSocket server = new ServerSocket(18888);
//循环监听客户端链接请求
while(true){
System.out.println("start...");
//接收请求
socket = server.accept();
System.out.println("accept...");
//接收客户端消息
BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
String message = in.readLine();
//发送消息，向客户端
PrintWriter out = new PrintWriter(new BufferedWriter(new OutputStreamWriter(socket.getOutputStream())),true);
out.println("Server:" + message);
//关闭流
in.close();
out.close();
}
} catch (IOException e) {
e.printStackTrace();
}finally{
if (null != socket){
try {
socket.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
//启动服务器
public static void main(String[] args){
Thread server = new Thread(new Server());
server.start();
}
}
客户端，MainActivity
public class MainActivity extends Activity {
private EditText editText;
private Button button;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
editText = (EditText)findViewById(R.id.editText1);
button = (Button)findViewById(R.id.button1);
button.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
Socket socket = null;
String message = editText.getText().toString()+ "\r\n" ;
try {
//创建客户端socket,注意:不能用localhost或127.0.0.1，Android模拟器把自己作为localhost
socket = new Socket("<span style="font-weight: bold;">10.0.2.2</span>",18888);
PrintWriter out = new PrintWriter(new BufferedWriter(new OutputStreamWriter
(socket.getOutputStream())),true);
//发送数据
out.println(message);
//接收数据
BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
String msg = in.readLine();
if (null != msg){
editText.setText(msg);
System.out.println(msg);
}
else{
editText.setText("data error");
}
out.close();
in.close();
} catch (UnknownHostException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
finally{
try {
if (null != socket){
socket.close();
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
});
}
}
布局文件：
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="fill_parent"
android:layout_height="fill_parent">
<TextView android:layout_width="fill_parent"
android:layout_height="wrap_content" android:text="@string/hello" />
<EditText android:layout_width="match_parent" android:id="@+id/editText1"
android:layout_height="wrap_content"
android:hint="input the message and click the send button"
></EditText>
<Button android:text="send" android:id="@+id/button1"
android:layout_width="fill_parent" android:layout_height="wrap_content"></Button>
</LinearLayout> 启动服务器：
javac com/test/socket/Server.java java com.test.socket.Server
运行客户端程序：
结果如图：
注意：服务器与客户端无法链接的可能原因有：
没有加访问网络的权限：<uses-permission android:name="android.permission.INTERNET"></uses-permission>
IP地址要使用：10.0.2.2
模拟器不能配置代理。
2。Apache接口
对于大部分应用程序而言JDK本身提供的网络功能已远远不够，这时就需要Android提供的Apache HttpClient了。它是一个开源项目，功能更加完善，为客户端的Http编程提供高效、最新、功能丰富的工具包支持。
下面我们以一个简单例子来看看如何使用HttpClient在Android客户端访问Web。
首先，要在你的机器上搭建一个web应用myapp，只有很简单的一个http.jsp
内容如下：
<%@page language="java" import="java.util.*" pageEncoding="utf-8"%>
<html>
<head>
<title>
Http Test
</title>
</head>
<body>
<%
String type = request.getParameter("parameter");
String result = new String(type.getBytes("iso-8859-1"),"utf-8");
out.println("<h1>" + result + "</h1>");
%>
</body>
</html>
然后实现Android客户端，分别以post、get方式去访问myapp,代码如下：
布局文件：
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
>
<TextView
android:gravity="center"
android:id="@+id/textView"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="@string/hello"
/>
<Button android:text="get" android:id="@+id/get" android:layout_width="match_parent" android:layout_height="wrap_content"></Button>
<Button android:text="post" android:id="@+id/post" android:layout_width="match_parent" android:layout_height="wrap_content"></Button>
</LinearLayout>
资源文件：
strings.xml
<?xml version="1.0" encoding="utf-8"?>
<resources>
<string name="hello">通过按钮选择不同方式访问网页</string>
<string name="app_name">Http Get</string>
</resources>
主Activity:
public class MainActivity extends Activity {
private TextView textView;
private Button get,post;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
textView = (TextView)findViewById(R.id.textView);
get = (Button)findViewById(R.id.get);
post = (Button)findViewById(R.id.post);
//绑定按钮监听器
get.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
//注意：此处ip不能用127.0.0.1或localhost,Android模拟器已将它自己作为了localhost
String uri = "http://192.168.22.28:8080/myapp/http.jsp?parameter=以Get方式发送请求";
textView.setText(get(uri));
}
});
//绑定按钮监听器
post.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
String uri = "http://192.168.22.28:8080/myapp/http.jsp";
textView.setText(post(uri));
}
});
}
/**
* 以get方式发送请求，访问web
* @param uri web地址
* @return 响应数据
*/
private static String get(String uri){
BufferedReader reader = null;
StringBuffer sb = null;
String result = "";
HttpClient client = new DefaultHttpClient();
HttpGet request = new HttpGet(uri);
try {
//发送请求，得到响应
HttpResponse response = client.execute(request);
//请求成功
if (response.getStatusLine().getStatusCode() == HttpStatus.SC_OK){
reader = new BufferedReader(new InputStreamReader(response.getEntity().getContent()));
sb = new StringBuffer();
String line = "";
String NL = System.getProperty("line.separator");
while((line = reader.readLine()) != null){
sb.append(line);
}
}
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
finally{
try {
if (null != reader){
reader.close();
reader = null;
}
} catch (IOException e) {
e.printStackTrace();
}
}
if (null != sb){
result = sb.toString();
}
return result;
}
/**
* 以post方式发送请求，访问web
* @param uri web地址
* @return 响应数据
*/
private static String post(String uri){
BufferedReader reader = null;
StringBuffer sb = null;
String result = "";
HttpClient client = new DefaultHttpClient();
HttpPost request = new HttpPost(uri);
//保存要传递的参数
List<NameValuePair> params = new ArrayList<NameValuePair>();
//添加参数
params.add(new BasicNameValuePair("parameter","以Post方式发送请求"));
try {
//设置字符集
HttpEntity entity = new UrlEncodedFormEntity(params,"utf-8");
//请求对象
request.setEntity(entity);
//发送请求
HttpResponse response = client.execute(request);
//请求成功
if (response.getStatusLine().getStatusCode() == HttpStatus.SC_OK){
System.out.println("post success");
reader = new BufferedReader(new InputStreamReader(response.getEntity().getContent()));
sb = new StringBuffer();
String line = "";
String NL = System.getProperty("line.separator");
while((line = reader.readLine()) != null){
sb.append(line);
}
}
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
finally{
try {
//关闭流
if (null != reader){
reader.close();
reader = null;
}
} catch (IOException e) {
e.printStackTrace();
}
}
if (null != sb){
result = sb.toString();
}
return result;
}
}