/*
* @(#) AddPanel.java
*/

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

public class AddPanel extends JFrame implements ActionListener {
private JPanel panel1;
private JPanel panel2;
private JButton button;

public AddPanel() {
panel1 = new JPanel();
panel1.setBackground(Color.gray);
Panel1Handler handler = new Panel1Handler();
panel1.addContainerListener(handler);
panel1.addComponentListener(handler);
add(panel1, BorderLayout.CENTER);

panel2 = new JPanel();
panel2.setBackground(Color.white);
panel2.setSize(200, 100);

button = new JButton("Add Panel");
button.addActionListener(this);
add(button, BorderLayout.SOUTH);

setSize(400, 300);
setVisible(true);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}

public void actionPerformed(ActionEvent event) {
panel1.add(panel2);
}

class Panel1Handler implements ContainerListener, ComponentListener {
public void componentAdded(ContainerEvent event) {
System.out.println("componentAdded");
panel1.repaint();
}

public void componentRemoved(ContainerEvent event) {
System.out.println("componentRemoved");
}

public void componentHidden(ComponentEvent event) {
System.out.println("componentHidden");
}

public void componentMoved(ComponentEvent event) {
System.out.println("componentMoved");
}

public void componentResized(ComponentEvent event) {
System.out.println("componentResized");
}

public void componentShown(ComponentEvent event) {
System.out.println("componentShown");
}
}

public static void main(String[] args) {
AddPanel application = new AddPanel();
}
}

注意：用JDK5.0版本编译执行。

程序运行后，单击 Add Panel 按钮后，可以正常添加并显示Panel2，但是当改变窗口大小后，Panel2就不能正常显示了，componentResized()方法里应该怎么添加什么代码？怎么写？ 程序其它地方是不是也有错误？

将componentResized()方法里的代码改成下面的也不行
public void componentResized(ComponentEvent event) {
Graphics g = panel1.getGraphics();
panel1.update(g);
}

[CODE]import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.ComponentEvent;
import java.awt.event.ComponentListener;
import java.awt.event.ContainerEvent;
import java.awt.event.ContainerListener;
public class AddPanel extends JFrame implements ActionListener {
private JPanel panel1;
private JPanel panel2;
private JButton button;
public AddPanel() {
panel1 = new JPanel();
panel1.setBackground(Color.gray);
Panel1Handler handler = new Panel1Handler();
panel1.addContainerListener(handler);
panel1.addComponentListener(handler);
add(panel1, BorderLayout.CENTER);

panel2 = new JPanel();
panel2.setBackground(Color.white);
panel2.setSize(200, 100);
button = new JButton("Add Panel");
button.addActionListener(this);
add(button, BorderLayout.SOUTH);

setSize(400, 300);
setVisible(true);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
public void actionPerformed(ActionEvent event) {
panel1.add(new JButton("新加的"));
SwingUtilities.updateComponentTreeUI(this);
}
class Panel1Handler implements ContainerListener, ComponentListener {
public void componentAdded(ContainerEvent event) {
System.out.println("componentAdded");
panel1.repaint();
}
public void componentRemoved(ContainerEvent event) {
System.out.println("componentRemoved");
}
public void componentHidden(ComponentEvent event) {
System.out.println("componentHidden");
}
public void componentMoved(ComponentEvent event) {
System.out.println("componentMoved");
}
public void componentResized(ComponentEvent event) {
System.out.println("componentResized");
}
public void componentShown(ComponentEvent event) {
System.out.println("componentShown");
}
}
public static void main(String[] args) {
AddPanel application = new AddPanel();
}
}[/CODE]

看看吧,你之所以会出现那个问题是因为JPanel本来就不是很明显的东西.加了和没加一样,我现在加的是一个按钮,然后调用了刷新整个组件树的方法,这样就可以立即看到了
你那个ContainerListener, ComponentListener 完全不用去加的

两个Panel的颜色是不同的，Panel1是灰色的，Panel2是白色的。

我的本意是这样的：
当单击 Add Panel 按钮后，改变窗口的大小不会影响到Panel2（就是那个白色区域（0，0，200，100））还是正常显示。

存在的问题：
但是现在当添加Panel2后，改变一下窗口的大小，然后Panel2就变成Panel1上方中央一个很小的白色小块了。

原是你想那样是吧

你把
panel2.setPreferredSize(new Dimension(200, 100));
替换你的
panel2.setSize(200, 100);
就可以了