问题：1.标题栏上的按钮没有显示；2.改进一下，将标题栏的高修改为25。

非常抱歉，我忘记在代码中设置标题栏的高度。以下是更新后的代码，包括添加了按钮和修改了标题栏的高度为25：

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

public class CustomWindow extends JFrame {
    private JPanel titleBarPanel;
    private JButton minimizeButton;
    private JButton maximizeButton;
    private JButton closeButton;

    public CustomWindow() {
        // 设置窗口大小和背景色
        this.setSize(1100, 700);
        this.getContentPane().setBackground(new Color(204, 204, 204));
        
        // 去除窗口边框默认样式
        this.setUndecorated(true);
        
        // 禁用窗口缩放
        this.setResizable(false);
        
        // 居中显示窗口
        Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
        int screenWidth = screenSize.width;
        int screenHeight = screenSize.height;
        int windowWidth = this.getWidth();
        int windowHeight = this.getHeight();
        int x = (screenWidth - windowWidth) / 2;
        int y = (screenHeight - windowHeight) / 2;
        this.setLocation(x, y);
        
        // 鼠标可以移动窗口
        titleBarPanel = new JPanel();
        titleBarPanel.setBackground(Color.WHITE);
        titleBarPanel.setPreferredSize(new Dimension(this.getWidth(), 25)); // 设置标题栏高度为25
        titleBarPanel.addMouseListener(new MouseAdapter() {
            private Point origin;

            @Override
            public void mousePressed(MouseEvent e) {
                origin = new Point(e.getX(), e.getY());
            }

            @Override
            public void mouseReleased(MouseEvent e) {
                origin = null;
            }
        });
        
        titleBarPanel.addMouseMotionListener(new MouseMotionAdapter() {
            @Override
            public void mouseDragged(MouseEvent e) {
                Point p = getLocation();
                setLocation(p.x + e.getX() - origin.x, p.y + e.getY() - origin.y);
            }
        });
        
        // 添加最小化、最大化和关闭按钮
        minimizeButton = new JButton(new ImageIcon("minimize.png"));
        maximizeButton = new JButton(new ImageIcon("maximize.png"));
        closeButton = new JButton(new ImageIcon("close.png"));
        
        minimizeButton.setBorderPainted(false);
        maximizeButton.setBorderPainted(false);
        closeButton.setBorderPainted(false);
        
        minimizeButton.setOpaque(false);
        maximizeButton.setOpaque(false);
        closeButton.setOpaque(false);
        
        minimizeButton.setContentAreaFilled(false);
        maximizeButton.setContentAreaFilled(false);
        closeButton.setContentAreaFilled(false);
        
        // 添加按钮功能
        minimizeButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                setExtendedState(JFrame.ICONIFIED);
            }
        });
        
        maximizeButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                if (getExtendedState() != JFrame.MAXIMIZED_BOTH) {
                    setExtendedState(JFrame.MAXIMIZED_BOTH);
                } else {
                    setExtendedState(JFrame.NORMAL);
                }
            }
        });
        
        closeButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                System.exit(0);
            }
        });
        
        // 高亮按钮
        minimizeButton.addMouseListener(new MouseAdapter() {
            @Override
            public void mouseEntered(MouseEvent e) {
                minimizeButton.setIcon(new ImageIcon("minimize_highlight.png"));
            }

            @Override
            public void mouseExited(MouseEvent e) {
                minimizeButton.setIcon(new ImageIcon("minimize.png"));
            }
        });
        
        maximizeButton.addMouseListener(new MouseAdapter() {
            @Override
            public void mouseEntered(MouseEvent e) {
                maximizeButton.setIcon(new ImageIcon("maximize_highlight.png"));
            }

            @Override
            public void mouseExited(MouseEvent e) {
                maximizeButton.setIcon(new ImageIcon("maximize.png"));
            }
        });
        
        closeButton.addMouseListener(new MouseAdapter() {
            @Override
            public void mouseEntered(MouseEvent e) {
                closeButton.setIcon(new ImageIcon("close_highlight.png"));
            }

            @Override
            public void mouseExited(MouseEvent e) {
                closeButton.setIcon(new ImageIcon("close.png"));
            }
        });
        
        // 将按钮添加到标题栏
        titleBarPanel.add(minimizeButton);
        titleBarPanel.add(maximizeButton);
        titleBarPanel.add(closeButton);
        
        // 将标题栏添加到窗口
        this.add(titleBarPanel, BorderLayout.NORTH);
        
        // 设置窗口关闭操作
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        
        this.setVisible(true);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                new CustomWindow();
            }
        });
    }
}

请确保将按钮图标文件替换为实际的图片文件，并确保这些图片文件存在于项目目录中。这次代码已经包括了标题栏高度的修改。希望这次能帮到你！如果还有其他问题，请随时提问。