选项卡成效的实现

import javax.microedition.lcdui.Command;import javax.microedition.lcdui.CommandListener;import javax.microedition.lcdui.Display;import javax.microedition.lcdui.Displayable;import javax.microedition.lcdui.Image;import javax.microedition.lcdui.List;import javax.microedition.midlet.MIDlet;import javax.microedition.midlet.MIDletStateChangeException;public class ListImage extends MIDlet implements CommandListener {    private Display display;        //定义List菜单的内容    private static String menuItems[] = {"Image1",            "Image2",            "No Image",            "Exit"    };    private Image image1;    private Image image2;        private List lstImplicitImage;        public ListImage() {        try {            image1 = Image.createImage("/Image1.gif");            image2 = Image.createImage("/Image2.gif");        } catch(Exception e) {            System.out.println("Image can not be loaded: " + e);        }                lstImplicitImage = new List(                "List Image Demo",                  //标题                List.IMPLICIT,                      //隐式类型                 menuItems,                          //设置列表内容                   new Image[]{                        //列表用图标                    image1, image1, image1, image2                });     }    protected void startApp() throws MIDletStateChangeException {        //设置命令监听        lstImplicitImage.setCommandListener(this);                //获得当前MIDlet的Display对象        display = Display.getDisplay(this);         //设置List对象为当前显示对象        display.setCurrent(lstImplicitImage);    }    protected void pauseApp() {        // TODO Auto-generated method stub    }    protected void destroyApp(boolean arg0)         throws MIDletStateChangeException {        // TODO Auto-generated method stub    }        /**     * 处理命令按钮事件     */    public void commandAction(Command c, Displayable d) {        if (c == List.SELECT_COMMAND) {            //获得被选中选项的索引            switch(lstImplicitImage.getSelectedIndex()) {            case 0:                setImage(image1);                break;            case 1:                setImage(image2);                break;            case 2:                setImage(null);                break;            case 3:                notifyDestroyed();            }        }    }        private void setImage(Image img) {        for(int i=0;i<lstImplicitImage.size();i++) {            lstImplicitImage.set(i,                     lstImplicitImage.getString(i), img);        }    }}