三个JComboBox连动的问题

Question

试试这个import java.awt.*;
import javax.swing.*;
import java.awt.Rectangle;
import java.awt.event.*;public class MComboButton extends JFrame {
    public MComboButton() {
        try {
            jbInit();
        }
        catch (Exception exception) {
            exception.printStackTrace();
        }
    }    private void jbInit() throws Exception {
        getContentPane().setLayout(null);
        jComboBox1.setBounds(new Rectangle(20, 20, 100, 20));
        jComboBox1.addItem("A");
        jComboBox1.addItem("B");
        this.getContentPane().add(jComboBox1);
        jComboBox1.addItemListener(new ItemListener() {
            public void itemStateChanged(ItemEvent e) {
                if (jComboBox1.getItemCount() != 0) {
                    String sTemp = jComboBox1.getSelectedItem().toString();
                    jComboBox2.removeAllItems();
                    jComboBox2.addItem(sTemp + "A");
                    jComboBox2.addItem(sTemp + "B");
                    jComboBox2.setSelectedIndex(0);
                }
            }
        });
        jComboBox2.setBounds(new Rectangle(140, 20, 100, 20));
        jComboBox2.addItemListener(new ItemListener() {
            public void itemStateChanged(ItemEvent e) {
                if (jComboBox2.getItemCount() != 0) {
                    String sTemp = jComboBox2.getSelectedItem().toString();
                    jComboBox3.removeAllItems();
                    jComboBox3.addItem(sTemp + "A");
                    jComboBox3.addItem(sTemp + "B");
                    jComboBox3.setSelectedIndex(0);
                }
            }
        });
        this.getContentPane().add(jComboBox2);
        jComboBox3.setBounds(new Rectangle(260, 20, 100, 20));        
        this.getContentPane().add(jComboBox3);
    }    public static void main(String[] args) {
        MComboButton mcombobutton = new MComboButton();
        mcombobutton.setSize(380, 100);
        mcombobutton.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        mcombobutton.show();
    }    JComboBox jComboBox1 = new JComboBox();
    JComboBox jComboBox2 = new JComboBox();
    JComboBox jComboBox3 = new JComboBox();}

Answer 1

有一点很奇怪,中午我在办公室试着写了一个,我记得没有去判断getItemCount().跟踪了一下remove的事件并没有触发itemStateChanged事件,怎么晚上回来重写就.....晕,明天回去好好再看一下.
还有一点,上面的程序在1.3下运行时,点出列表后点其中一项时(mousePressed)下面的窗体会失去焦点,再mouseReleased时窗体恢复焦点,而1.4的窗体一直有焦点,这难道就是传说中的升级版本的改进??