爲選擇框添加事件

 //ComboBox.java
//爲選擇框添加事件
//2009-11-19

//<applet code=ComboBox1 width=200 height=100>
//</applet>

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

public class  ComboBox1 extends JApplet
{
 String[] choiceItem={"choice1","choice2","choice3","choice4"};
 JComboBox box=new JComboBox(choiceItem);
 JTextField txt1=new JTextField(15);
 JTextArea txt2=new JTextArea(15,15);

 class ActionLis implements ActionListener
 {
  public void actionPerformed(ActionEvent e){
   txt1.setText("index"+box.getSelectedIndex()+":"+
    ((JComboBox)e.getSource()).getSelectedItem());
  }  
 }

 class ItemLis implements ItemListener
 {
  public void itemStateChanged(ItemEvent e){
   txt2.append(e.paramString()+"/n");
  }
 }

 public void init(){
  Container cp=getContentPane();
  cp.setLayout(new FlowLayout());
  cp.add(box);
  cp.add(txt1);
  cp.add(new JScrollPane(txt2));

  box.addActionListener(new ActionLis());
  box.addItemListener(new ItemLis());
 }
}