谈谈Android的三种网络通信方式

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：

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; 
   
  @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; 
   
  @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)); 
      } 
    }); 
  } 
   
  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; 
  } 
   
  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; 
  } 
} 

运行结果如下：

3.android.net编程：

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。这里不详细讲。

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