用Java創建帶圖像的菜單

2019-11-18 13:37:35

字體：大中小

來源：轉載

供稿：網友

　　在Windows的“開始”菜單上，會在菜單左側顯示一幅圖像。很多基于Windows的軟件也有類似效果的菜單。用java Swing可以制作出類似效果的菜單嗎？答案當然是肯定的，而且非常簡單。

我們首先從Swing的JPopupMenu組件進行擴展，讓其接受一個圖片，顯示在左側；或者接受一個字符串，動態生成圖片后，在顯示在左側。為了避免預備圖片的麻煩，我們就以動態生成內存圖片為例，編寫一個JImagedPopupMenu類。

JImagedPopupMenu在創建時可以接受一個字符串，生成一副內存圖片BufferedImage。然后，我們需要覆蓋JComponent的getInsets方法，重新計算Inset的left值，將其在原數值基礎上加上圖片的寬度，然后返回：

?public Insets getInsets() {
??????? Insets insets = (Insets)super.getInsets().clone();
??????? insets.left += imageIcon.getIconWidth();
??????? return insets;
??? }

最后，覆蓋paintComponent方法，在原基礎上增加圖片的繪制：
??? 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);
??????? }
??? }

完整代碼如下：

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();

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