在Windows的“开始”菜单上，会在菜单左侧显示一幅图像。很多基于Windows的软件也有类似效果的菜单。用Java Swing可以制作出类似效果的菜单吗？答案当然是肯定的，而且非常简单。

我们首先从Swing的JPopupMenu组件进行扩展，让其接受一个图片，显示在左侧；或者接受一个字符串，动态生成图片后，在显示在左侧。为了避免准备图片的麻烦，我们就以动态生成内存图片为例，编写一个JImagedPopupMenu类。

JImagedPopupMenu在创建时可以接受一个字符串，生成一副内存图片BufferedImage。然后，我们需要覆盖JComponent的getInsets方法，重新计算Inset的left值，将其在原数值基础上加上图片的宽度，然后返回：

public Insets getInsets() {

Insets insets = (Insets)super.getInsets().clone();

insets.left += imageIcon.getIconWidth();

return insets;

}

最后，覆盖paintComponent方法，在原基础上增加图片的绘制：

public void paintComponent(Graphics g) {

super.paintComponent(g);

if (imageIcon != null) {

Insets insets = getInsets();

g.drawImage(imageIcon.getImage(),

insets.left - imageIcon.getIconWidth(),

insets.top,

null);

}

}

完整代码如下：

import java.awt.*;

import java.awt.event.*;

import java.awt.geom.*;

import java.awt.image.*;

import javax.swing.*;

public class ImageMenu extends JPopupMenu {

private Font font = new Font("Dialog", Font.BOLD, 13);

private ImageIcon imageIcon = null;

public ImageMenu(ImageIcon imageIcon) {

this.imageIcon = imageIcon;

}

public ImageMenu(String text) {

this.imageIcon = createImage(text);

}

private ImageIcon createImage(String text) {

BufferedImage bi = new BufferedImage(30, 1000, BufferedImage.TYPE_INT_ARGB);

ImageIcon image = new ImageIcon(bi);

Graphics2D g2d = bi.createGraphics();

GradientPaint paint = new GradientPaint(0, 0, Color.yellow, 30, 10, Color.red, true);

g2d.setPaint(paint);

g2d.fillRect(0, 0, bi.getWidth(), bi.getHeight());

AffineTransform at = new AffineTransform();

at.rotate( -Math.PI / 2);

g2d.setTransform(at);

g2d.setColor(Color.white);

g2d.setFont(font);

g2d.drawString(text, -180, bi.getWidth() / 2);

return image;

}

public Insets getInsets() {

Insets insets = (Insets)super.getInsets().clone();

insets.left += imageIcon.getIconWidth();

return insets;

}

public void paint(Graphics g) {

super.paint(g);

if (imageIcon != null) {

Insets insets = getInsets();

g.drawImage(imageIcon.getImage(),

insets.left - imageIcon.getIconWidth(),

insets.top,

null);

}

}

public static void main(String[] args) {

final JFrame frame = new JFrame();

frame.setSize(600, 500);

frame.setTitle("ImageMenu");

final ImageMenu menu = new ImageMenu("Windows XP Perfessional");

menu.add(new JMenuItem("Winzip 8.0"));

menu.addSeparator();

menu.add(new JMenuItem("Programs"));

menu.add(new JMenuItem("Document"));

menu.add(new JMenuItem("Settings"));

menu.add(new JMenuItem("Search"));

menu.add(new JMenuItem("Help and Support"));

menu.add(new JMenuItem("Run..."));

menu.addSeparator();

menu.add(new JMenuItem("Shut Down..."));

JLabel label = new JLabel("Right click me to show image popup menu.");

label.addMouseListener(new java.awt.event.MouseAdapter() {

public void mouseReleased(MouseEvent e) {

if (e.isPopupTrigger()) {

menu.show(frame, e.getPoint().x, e.getPoint().y);

}

}

});

frame.getContentPane().add(label, BorderLayout.CENTER);

frame.show();

}

}

同样，采用这种方法，也可以将JMenu扩展出同样的效果