J2ME无线联网技术中的HTTP连接[转]

import java.io.ByteArrayOutputStream;
import java.io.DataInputStream;
import java.io.IOException;

import javax.microedition.io.Connector;
import javax.microedition.io.ContentConnection;
import javax.microedition.lcdui.Alert;
import javax.microedition.lcdui.AlertType;
import javax.microedition.lcdui.Command;
import javax.microedition.lcdui.CommandListener;
import javax.microedition.lcdui.Display;
import javax.microedition.lcdui.Displayable;
import javax.microedition.lcdui.Form;
import javax.microedition.lcdui.Image;
import javax.microedition.lcdui.ImageItem;
import javax.microedition.lcdui.TextBox;
import javax.microedition.midlet.MIDlet;
import javax.microedition.midlet.MIDletStateChangeException;

/**
* 在运行的TextBox输入框中输入一个图片的网址,下载到模拟器中
*
* 例如:在输入框中输入:www.baidu.com/img/logo.gif
*
* @author mao
*
*/
public class ViewImage extends MIDlet implements CommandListener {

    private Display display;
    private TextBox tbMain;
    private Alert alStatus;
    private Form fm;
    private Command cmExit;
    private Command cmView;
    private Command cmBack;
    private static final int ALERT_DISPLAY_TIME = 3000;
    Image im = null;

    public ViewImage() {
        display = Display.getDisplay(this);
        tbMain = new TextBox("输入图片地址:", "http://", 75, 0);
        cmExit = new Command("退出", Command.EXIT, 1);
        cmView = new Command("下载", Command.SCREEN, 2);
        tbMain.addCommand(cmExit);
        tbMain.addCommand(cmView);
        tbMain.setCommandListener(this);
        fm = new Form("");
        cmBack = new Command("后退", Command.BACK, 1);
        fm.addCommand(cmBack);
        fm.setCommandListener(this);
    }

    protected void destroyApp(boolean arg0) throws MIDletStateChangeException {
    }

    protected void pauseApp() {
    }

    protected void startApp() throws MIDletStateChangeException {
        display.setCurrent(tbMain);
    }

    public void commandAction(Command c, Displayable s) {
        if (c == cmExit) {
            try {
                destroyApp(false);
                notifyDestroyed();
            } catch (MIDletStateChangeException e) {
                e.printStackTrace();
            }
        } else if (c == cmView) {
            showAlert("下载中...", false, tbMain);
            Download dl = new Download(tbMain.getString(), this);
            dl.start();
        } else if (c == cmBack) {
            display.setCurrent(tbMain);
        }
    }

    public void showImage(boolean flag) {
        if (flag == false)
            showAlert("下载失败...", true, tbMain);
        else {
            ImageItem ii = new ImageItem(null, im, ImageItem.LAYOUT_DEFAULT,
                    null);
            if (fm.size() != 0)
                fm.set(0, ii);
            else
                fm.append(ii);
            showAlert("下载成功", true, fm);
        }
    }

    public void showAlert(String msg, boolean modal, Displayable displayable) {
        alStatus = new Alert("状态", msg, null, AlertType.INFO);
        if (modal)
            alStatus.setTimeout(Alert.FOREVER);
        else
            alStatus.setTimeout(ALERT_DISPLAY_TIME);
        display.setCurrent(alStatus, displayable);
    }
}

class Download implements Runnable {

    private String url;
    private ViewImage Midlet;
    private boolean downloadSuccess = false;

    public Download(String url, ViewImage Midlet) {
        this.url = url;
        this.Midlet = Midlet;
    }

    public void run() {
        try {
            getImage(url);
        } catch (Exception e) {
            System.err.println("Msg : " + e.toString());
        }
    }

    public void start() {
        Thread thread = new Thread(this);
        try {
            thread.start();
        } catch (Exception e) {
        }
    }

    private void getImage(String url) throws IOException {

        System.out.println();
       
        System.out.println("this is the url : " + url);

        ContentConnection connection = (ContentConnection) Connector.open(url);

        System.out.println("connection : " + connection);

        DataInputStream iStrm = connection.openDataInputStream();
       
        System.out.println("iStrm: " + iStrm);
       
        ByteArrayOutputStream bStrm = null;
        Image im = null;
        try {
            byte imageData[];
            int length = (int) connection.getLength();
            if (length != -1) {
                imageData = new byte[length];
                iStrm.readFully(imageData);
            } else {
                bStrm = new ByteArrayOutputStream();
                int ch;
                while ((ch = iStrm.read()) != -1)
                    bStrm.write(ch);
                imageData = bStrm.toByteArray();
            }
            im = Image.createImage(imageData , 0 , imageData.length);
        } finally {
            if (connection != null)
                connection.close();
            if (iStrm != null)
                iStrm.close();
            if (bStrm != null)
                bStrm.close();
        }
        if (im == null)
            Midlet.showImage(false);
        else {
            Midlet.im = im;
            Midlet.showImage(true);
        }
    }
}

 

 

 

http://www.java-cn.com/club/html/63/n-163-3.htmlj2me最佳联网方案终结版

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