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用 Java 创建带图像的菜单来美化界面


  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
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