Я не уверен, возможно ли это, но есть ли способ безопасно позволить всплывающим окнам быть прозрачными, даже если родительский контейнер также является полупрозрачным?

Если не,what would be wise alternative to use or extend instead of JPopupMenu?

Замечания:Translucent относится к компоненту, не имеющему «фон», подобному эффектуsetOpaque(false);, Благодарю.

От форума ответ пользователяcamickr в 2009:

I don't know if transparency painting has changed in 1.6.0_10. Prior to that I believe transparency can only be achieved in lightweight components (ie. Swing does all the painting). JFrame, JWindow and JDialog are not lightweight because they use OS components.

In the case of a popup, it is lightweight when entirely contained within its parent frame. But a lightweight popup can not be painted outside the bounds of the frame so a JWindow (I believe) is used as the popup, which can't be transparent.

SSCCE: Отображение прозрачного JWindow поверх прозрачного JFrame

<code>import com.sun.awt.AWTUtilities;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.*;

public class OpaqueWindowSSCCE {

    private int countdown = 5;

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

    public OpaqueWindowSSCCE() {
        final JFrame frame = new JFrame("OpaqueWindowSSCCE");
        final JWindow window = new JWindow();

        new Timer(1000, new ActionListener(){

            @Override
            public void actionPerformed(ActionEvent e) {
                if(--countdown == 0){
                    frame.dispose();
                    window.dispose();
                    System.exit(0);
                } else {
                    frame.repaint();
                }
            }

        }).start();

        frame.setContentPane(new JPanel() {

            @Override
            public void paintComponent(Graphics paramGraphics) {
                super.paintComponent(paramGraphics);
                Graphics2D g = (Graphics2D) paramGraphics.create();
                g.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
                g.setColor(new Color(50, 50, 50));
                g.fillRoundRect(0, 0, getWidth(), getHeight(), 10, 10);
                g.setColor(new Color(180, 180, 180));
                g.drawString("Closing in " + countdown + " seconds", 20, 25);
            }
        });

        window.setContentPane(new JPanel() {

            @Override
            public void paintComponent(Graphics paramGraphics) {
                super.paintComponent(paramGraphics);
                Graphics2D g = (Graphics2D) paramGraphics.create();
                g.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
                g.setColor(new Color(180, 180, 180));
                g.fillRoundRect(0, 0, getWidth(), getHeight(), 10, 10);
            }
        });

        frame.setUndecorated(true);

        ((JComponent) frame.getContentPane()).setOpaque(false);
        ((JComponent) window.getContentPane()).setOpaque(false);

        AWTUtilities.setWindowOpaque(frame, false);
        AWTUtilities.setWindowOpaque(window, false);

        window.setAlwaysOnTop(true);

        frame.setBounds(200,200,500,500);
        window.setBounds(600,600,200,200);
        frame.setVisible(true);
        window.setVisible(true);
    }
}
</code>