要创建透明窗口，您需要将框架背景色的
Alpha设置为0。这可能是我一段
时间以来看到的最不直观的调用，就好像您对任何其他Swing组件执行此操作一样，您将完全
搞砸绘制过程。
您不想更改窗口的不透明度，因为它会影响
整个窗口，并且其内容均等。
例如…
JWindow frame = new JWindow();frame.setBackground(new Color(0, 0, 0, 0));
frame.setBackground(new Color(0, 0, 0, 0));
您不必使用JWindow，但这意味着我不需要
自己修饰它…
您还需要确保添加到窗口的任何内容都是
透明的（opaque = false），以便它不会“隐藏”其下面的
内容……
import java.awt.Color;import java.awt.Dimension;import java.awt.EventQueue;import java.awt.Graphics;import java.awt.Graphics2D;import java.awt.GridBagLayout;import java.awt.event.ActionEvent;import java.awt.event.ActionListener;import java.awt.image.BufferedImage;import java.io.IOException;import javax.imageio.ImageIO;import javax.swing.JButton;import javax.swing.JPanel;import javax.swing.JWindow;import javax.swing.UIManager;import javax.swing.UnsupportedLookAndFeelException;import javax.swing.border.CompoundBorder;import javax.swing.border.EmptyBorder;import javax.swing.border.LineBorder;public class LeafWindow { public static void main(String[] args) { new LeafWindow(); } public LeafWindow() { EventQueue.invokeLater(new Runnable() { @Override public void run() { try { UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName()); } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) { } JWindow frame = new JWindow(); frame.setBackground(new Color(0, 0, 0, 0)); frame.setContentPane(new LeafPane()); frame.pack(); frame.setLocationRelativeTo(null); frame.setVisible(true); frame.setAlwaysonTop(true); } }); } public class LeafPane extends JPanel { private BufferedImage leaf; public LeafPane() { setBorder(new CompoundBorder( new LineBorder(Color.RED), new EmptyBorder(0, 0, 250, 0))); try { leaf = ImageIO.read(getClass().getResource("/Leaf.png")); } catch (IOException ex) { ex.printStackTrace(); } setOpaque(false); setLayout(new GridBagLayout()); JButton button = new JButton("Close"); button.addActionListener(new ActionListener() { @Override public void actionPerformed(ActionEvent e) { System.exit(0); } }); add(button); } @Override public Dimension getPreferredSize() { return leaf == null ? new Dimension(200, 200) : new Dimension(leaf.getWidth(), leaf.getHeight()); } @Override protected void paintComponent(Graphics g) { super.paintComponent(g); if (leaf != null) { Graphics2D g2d = (Graphics2D) g.create(); g2d.drawImage(leaf, 0, 0, this); g2d.dispose(); } } }}本示例故意为内容添加线边框，因为您可以看到原始的窗口边界。它还使用aEmptyBorder强制将其
JButton拖到图形上，但这只是一个示例……
