java - Windows 10 中无法使用透明 JFrame 背景吗？

Question

我在未修饰的 JFrame 中有一个 JPanel。我想在 JPanel 上绘制图像。当图像包含透明像素时，我希望它们是“透明的”，以便您可以看到窗口后面的任何内容。

我所有的研究都告诉我，我应该做

myJFrame.setUndecorated(true);
myJFrame.setBackground(new Color(0,0,0,0));
myJPanel.setOpaque(false);

，但是一旦我的 JFrame 背景颜色的 alpha 值不是 255，我的 JPanel 就不再被吸引。

Answer 1

因此，根据我有限的测试，它似乎在 Windows 10 上运行良好

import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
import javax.swing.border.LineBorder;

public class Test {

    public static void main(String[] args) {
        new Test();
    }

    public Test() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    try {
                        UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                    } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                        ex.printStackTrace();
                    }

                    JFrame frame = new JFrame("Testing");
                    frame.setUndecorated(true);
                    frame.setBackground(new Color(0, 0, 0, 0));
                    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                    frame.setContentPane(new TestPane());
                    frame.pack();
                    frame.setLocationRelativeTo(null);
                    frame.setVisible(true);
                } catch (IOException ex) {
                    ex.printStackTrace();
                }
            }
        });
    }

    public class TestPane extends JPanel {

        private BufferedImage img;

        public TestPane() throws IOException {
            img = ImageIO.read(...);
            setOpaque(false);
            setBorder(new LineBorder(Color.RED));
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(img.getWidth(), img.getHeight());
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            Graphics2D g2d = (Graphics2D) g.create();
            int x = (getWidth() - img.getWidth()) / 2;
            int y = (getHeight() - img.getHeight()) / 2;
            g2d.drawImage(img, x, y, this);
            g2d.dispose();
        }

    }

}

为了确定，我使用 JLabel 进行了测试...

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
import javax.swing.border.LineBorder;

public class Test {

    public static void main(String[] args) {
        new Test();
    }

    public Test() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    try {
                        UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                    } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                        ex.printStackTrace();
                    }

                    JFrame frame = new JFrame("Testing");
                    frame.setUndecorated(true);
                    frame.setBackground(new Color(0, 0, 0, 0));
                    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                    frame.setContentPane(new TestPane());
                    frame.pack();
                    frame.setLocationRelativeTo(null);
                    frame.setVisible(true);
                } catch (IOException ex) {
                    ex.printStackTrace();
                }
            }
        });
    }

    public class TestPane extends JPanel {

        public TestPane() throws IOException {
            BufferedImage img = ImageIO.read(...);
            setOpaque(false);
            setBorder(new LineBorder(Color.RED));
            setLayout(new BorderLayout());
            add(new JLabel(new ImageIcon(img)));
        }

    }

}

这表明问题出在您未向我们展示的代码中的某个位置。考虑提供 runnable example这说明了你的问题。这不是代码转储，而是您正在执行的操作的示例，它突出显示了您遇到的问题。这将减少困惑并获得更好的响应