j2me的form和command的應用

import javax.microedition.lcdui.*;
import javax.microedition.midlet.MIDlet;

public class AppMain extends MIDlet implements CommandListener{
 public Form f;
 public Command cmd_back;
 public Command cmd_gotof1;
 public Form f2;
 public Image im;
 public AppMain()
 {
  f=new Form("歡迎你的到來");
  f.append("我來了");
  f2=new Form("歡迎你的到來");
  f2.append("我又來了");
  cmd_back=new Command("返回",Command.SCREEN,2);
  cmd_gotof1=new Command("進去",Command.SCREEN,1);
  f.addCommand(cmd_back);
  try
  {
   im=Image.createImage("/a.png");
  }
  catch(Exception e)
  {
   System.out.println(e.getMessage());
  }
  if(im!=null)
  {
   f2.append(im);
  }
  
  f.addCommand(cmd_gotof1);
  f2.addCommand(cmd_back);
  f.setCommandListener(this);
  f2.setCommandListener(this);
  
 }
 public void startApp()
 {
  Display.getDisplay(this).setCurrent(f);
 }
 public void pauseApp()
 {
  
 }
 public void destroyApp(boolean f)
 {
  
 }
 public void commandAction(Command c, Displayable arg1) {
  if(c==cmd_back)
  {
   Display.getDisplay(this).setCurrent(f);
  }
  if(c==cmd_gotof1)
  {
   Display.getDisplay(this).setCurrent(f2);
  }
 }

}