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開發適應中國網絡的J2ME連網程序(4)

編輯：J2ME

3 .5 讀取wml數據

經過上面的代碼示例，我們知道怎麼樣獲取到一張圖片了，此節我將給大家講解下怎麼樣去奪取網站的wml數據。廢話少說，我們只需要在上面的基礎上加多一個方法就可以了。

下面是代碼示例

import Javax.microedition.lcdui.*;
import Java.io.IOException;
import Javax.microedition.io.HttpConnection;
import Javax.microedition.io.Connection;
import Javax.microedition.io.Connector;
import Java.io.InputStream;
import Java.io.ByteArrayOutputStream;
/**
* <p>Title: p>
*
* <p>Description: p>
*
* <p>Copyright: Copyright (c) 2009p>
*
* <p>Company: p>
*
* @author not attributable
* @version 1.0
*/
public class ImageForm extends Form implements CommandListener {
Command iHttp = new Command("http", Command.BACK, Command.ITEM);
Command IExit = new Command("Exit", Command.EXIT, 1);
public ImageForm() {
super("ShowImage");
try {
jbInit();
}
catch(Exception e) {
e.printStackTrace();
}
}
private void jbInit() throws Exception {
// Set up this Displayable to listen to command events
setCommandListener(this);
// add the Exit command
addCommand(IExit);
addCommand(iHttp);
}
public void commandAction(Command aCommand, Displayable aDisplayable) {
/** @todo Add command handling code */
if (aCommand == IExit) {
// stop the MIDlet
HttpDemo.quitApp();
}else if(aCommand == iHttp){
startRqeusetHttpImage();
}
}
/**
* startReqeustSocketImage
*/
private void startReqeustSocketImage() {

}
/**
* 執行請求
*
*/
private void startRqeusetHttpImage() {
//一般來說，操作網絡等有阻塞的動作最好是啟動一個線程。
new Thread() {
public void run() {
HttpConnection sHttp = null;
InputStream sIs = null;
try {
append("Strart Request");
append("");
sHttp = (HttpConnection) openConnection("/School/UploadFiles_7810/201202/20120215183042180.png", 0);
sHttp.setRequestMethod(HttpConnection.GET);//設置請求方法，如果不設置的話，則系統默認的請求就是GET請求
sHttp.setRequestProperty("User-Agent", "Openwave"); //設置UA參數
sHttp.setRequestProperty("connection", "close");

int sCode = sHttp.getResponseCode();
if(sCode == 200){
sIs = sHttp.openDataInputStream();
byte [] sImageData = readDataFromStream(sIs, 512);
if(sImageData != null)
append(Image.createImage(sImageData, 0 , sImageData.length));
}

}
catch (Exception ex1) {
append(ex1.toString());
}finally{
//一般來說，close數據，一般寫在finally方法，這樣可以保證到如果程序出現任何問題都可以關閉連接，防止連接洩漏
try {
sIs.close();
sHttp.close();
} catch (IOException ex) {
}
}
}
}.start();
}

/**
* 創建一個連接
* @param aUrl String
* @param aNetworType int 0--CMNET ； 1--CMWAP
* @return Connection
*/
final Connection openConnection(String aUrl, int aNetworType){
Connection sConnection = null;
try{
if (aNetworType == 0) {
sConnection = Connector.open(aUrl);
} else {
HttpConnection sHttp = (HttpConnection) Connector.
open("http://10.0.0.172:80");
sHttp.setRequestProperty("X-Online-Host",
aUrl);
sConnection = sHttp;
}
}catch(Exception e){
append("Open Error=>" + e.toString());
}
return sConnection;
}

/**
* 從輸入流中讀取數據
* @param aIs InputStream
* @param aCache int //設置緩存大小，這個參數比較重要，設置大了，速度不一定快，因此得測試根據經驗找個平衡點
* @return byte[]
*/
final byte[] readDataFromStream(InputStream aIs, int aCache){
byte[] sData = null;
Java.io.ByteArrayOutputStream bos = new ByteArrayOutputStream();
try{
byte[] sCaceh = new byte[aCache];
int pos = 0;
int hasRead = 0;
while ((pos = aIs.read(sCaceh, 0, aCache)) != -1) {
hasRead += pos;
bos.write(sCaceh, 0, pos);
}
sData = bos.toByteArray();
}catch(Exception e){

}
return sData ;
}
}