談談Android的三種網絡通信方式

Android平台有三種網絡接口可以使用，他們分別是：java.net.*(標准Java接口)、Org.apache接口和Android.net.*(Android網絡接口)。下面分別介紹這些接口的功能和作用。

1.標准Java接口

java.net.*提供與聯網有關的類，包括流、數據包套接字(socket)、Internet協議、常見Http處理等。比如：創建URL，以及URLConnection/HttpURLConnection對象、設置鏈接參數、鏈接到服務器、向服務器寫數據、從服務器讀取數據等通信。這些在Java網絡編程中均有涉及，我們看一個簡單的socket編程，實現服務器回發客戶端信息。

服務端：

public class Server implements Runnable{ 
  @Override 
  public void run() { 
    Socket socket = null; 
    try { 
      ServerSocket server = new ServerSocket(18888); 
      //循環監聽客戶端鏈接請求 
      while(true){ 
        System.out.println("start..."); 
        //接收請求 
        socket = server.accept(); 
        System.out.println("accept..."); 
        //接收客戶端消息 
        BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream())); 
        String message = in.readLine(); 
        //發送消息，向客戶端 
        PrintWriter out = new PrintWriter(new BufferedWriter(new OutputStreamWriter(socket.getOutputStream())),true); 
        out.println("Server:" + message); 
        //關閉流 
        in.close(); 
        out.close(); 
      } 
    } catch (IOException e) { 
      e.printStackTrace(); 
    }finally{ 
      if (null != socket){ 
        try { 
          socket.close(); 
        } catch (IOException e) { 
          e.printStackTrace(); 
        } 
      } 
    } 
     
  } 
  //啟動服務器 
  public static void main(String[] args){ 
    Thread server = new Thread(new Server()); 
    server.start(); 
  } 
} 

客戶端，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 { 
          //創建客戶端socket,注意:不能用localhost或127.0.0.1，Android模擬器把自己作為localhost 
          socket = new Socket("<span >10.0.2.2</span>",18888); 
          PrintWriter out = new PrintWriter(new BufferedWriter(new OutputStreamWriter 
              (socket.getOutputStream())),true); 
          //發送數據 
          out.println(message); 
           
          //接收數據 
          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> 

啟動服務器：

javac com/test/socket/Server.java 
java com.test.socket.Server 

運行客戶端程序：

結果如圖：

注意：服務器與客戶端無法鏈接的可能原因有：

沒有加訪問網絡的權限：<uses-permission android:name="android.permission.INTERNET"></uses-permission>

IP地址要使用：10.0.2.2

模擬器不能配置代理。

2。Apache接口

對於大部分應用程序而言JDK本身提供的網絡功能已遠遠不夠，這時就需要Android提供的Apache HttpClient了。它是一個開源項目，功能更加完善，為客戶端的Http編程提供高效、最新、功能豐富的工具包支持。

下面我們以一個簡單例子來看看如何使用HttpClient在Android客戶端訪問Web。

首先，要在你的機器上搭建一個web應用myapp，只有很簡單的一個http.jsp

內容如下：

<%@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> 

然後實現Android客戶端，分別以post、get方式去訪問myapp,代碼如下：

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> 

資源文件：

strings.xml

<?xml version="1.0" encoding="utf-8"?> 
<resources> 
  <string name="hello">通過按鈕選擇不同方式訪問網頁</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); 
     
    //綁定按鈕監聽器 
    get.setOnClickListener(new OnClickListener() { 
      @Override 
      public void onClick(View v) { 
        //注意：此處ip不能用127.0.0.1或localhost,Android模擬器已將它自己作為了localhost 
        String uri = "http://192.168.22.28:8080/myapp/http.jsp?parameter=以Get方式發送請求"; 
        textView.setText(get(uri)); 
      } 
    }); 
    //綁定按鈕監聽器 
    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方式發送請求，訪問web 
   * @param uri web地址 
   * @return 響應數據 
   */ 
  private static String get(String uri){ 
    BufferedReader reader = null; 
    StringBuffer sb = null; 
    String result = ""; 
    HttpClient client = new DefaultHttpClient(); 
    HttpGet request = new HttpGet(uri); 
    try { 
      //發送請求，得到響應 
      HttpResponse response = client.execute(request); 
       
      //請求成功 
      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方式發送請求，訪問web 
   * @param uri web地址 
   * @return 響應數據 
   */ 
  private static String post(String uri){ 
    BufferedReader reader = null; 
    StringBuffer sb = null; 
    String result = ""; 
    HttpClient client = new DefaultHttpClient(); 
    HttpPost request = new HttpPost(uri); 
     
    //保存要傳遞的參數 
    List<NameValuePair> params = new ArrayList<NameValuePair>(); 
    //添加參數 
    params.add(new BasicNameValuePair("parameter","以Post方式發送請求")); 
     
    try { 
      //設置字符集 
      HttpEntity entity = new UrlEncodedFormEntity(params,"utf-8"); 
      //請求對象 
      request.setEntity(entity); 
      //發送請求 
      HttpResponse response = client.execute(request); 
       
      //請求成功 
      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 { 
        //關閉流 
        if (null != reader){ 
          reader.close(); 
          reader = null; 
        } 
      } catch (IOException e) { 
        e.printStackTrace(); 
      } 
    } 
    if (null != sb){ 
      result = sb.toString(); 
    } 
    return result; 
  } 
} 

運行結果如下：

3.android.net編程：

常常使用此包下的類進行Android特有的網絡編程，如：訪問WiFi，訪問Android聯網信息，郵件等功能。這裡不詳細講。

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