j2me学习笔记【3】——简单的在线帮助示例

package mtk;

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.TextBox;
import javax.microedition.midlet.MIDlet;
import javax.microedition.midlet.MIDletStateChangeException;

public class OnlineHelp extends MIDlet implements CommandListener {
private Display display;
private final static Command CMD_BACK=new Command("返回",Command.BACK,1);
private final static Command CMD_EXIT=new Command("退出",Command.EXIT,1);
private final static Command CMD_HELP=new Command("帮助",Command.HELP,1);
private Form mainForm;
private TextBox helpMsg;
public OnlineHelp() {
display=Display.getDisplay(this);
mainForm=new Form("在线帮助实例");
helpMsg=new TextBox("在线帮助","按“返回”回到上一屏幕，按“退出”退出当前应用程序",81,0);
helpMsg.addCommand(CMD_BACK);
helpMsg.setCommandListener(this);
mainForm.addCommand(CMD_EXIT);
mainForm.addCommand(CMD_HELP);
mainForm.setCommandListener(this);
}

protected void destroyApp(boolean arg0){
}

protected void pauseApp() {
}

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

public void commandAction(Command c, Displayable d) {
if(d.equals(mainForm)){
if(c==CMD_EXIT){
destroyApp(false);
notifyDestroyed();
}else if(c==CMD_HELP){
display.setCurrent(helpMsg);
}
}else if(d.equals(helpMsg)){
if(c==CMD_BACK){
display.setCurrent(mainForm);
}
}
}
}