How can i make a JPopupMenu transparent?

I'd like to customize the look of JPopupMenu so i made a custom class extending the JPopupMenu class on i overrode the paintComponent method as i would do for any component i need to customize.

public class CustomPopupMenu extends JPopupMenu {

    @Override
    public paintComponent(Graphics g) {
        //custom draw
    }
}

The only problem i have right know is that i'm not able to make the JPopupMenu transparent. I though setOpaque(false) would be enough, i was wrong.

How can i make a JPopupMenu transparent?

The problem with a popup menu is that it may be realized as a top-level container (Window), and a window is opaque, no matter what value you set with setOpaque(), its opaque. But windows can be made translucent, too.

You can hack it by forcing the use of a heavyweight popup and brutally altering its opacity. Try this as a starting base for experiments (Java7):

import java.awt.Window;

import javax.swing.JPopupMenu;
import javax.swing.SwingUtilities;

public class TranslucentPopup extends JPopupMenu {

    {
        // need to disable that to work
        setLightWeightPopupEnabled(false);
    }

    @Override
    public void setVisible(boolean visible) {
        if (visible == isVisible())
            return;
        super.setVisible(visible);
        if (visible) {
            // attempt to set tranparency
            try {
                Window w = SwingUtilities.getWindowAncestor(this);
                w.setOpacity(0.667F);
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }

}

Note that it will not make submenus translucent!

jpopupmenu is a window?

yes JPopup is container, for example

code for Java6 (have to change imports for Java7)

import java.awt.*;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import javax.swing.*;

public class TranslucentWindow extends JFrame {

    private static final long serialVersionUID = 1L;
    private JMenuItem m_mniInsertRow;
    private JMenuItem m_mniInsertScrip;
    private JMenuItem m_mniDeleterRow;
    private JMenuItem m_mniDeleteExpiredScrip;
    private JMenuItem m_mniSetAlert;

    public TranslucentWindow() {
        super("Test translucent window");
        setLayout(new FlowLayout());
        add(new JButton("test"));
        add(new JCheckBox("test"));
        add(new JRadioButton("test"));
        add(new JProgressBar(0, 100));
        JPanel panel = new JPanel() {

            @Override
            public Dimension getPreferredSize() {
                return new Dimension(400, 300);
            }
            private static final long serialVersionUID = 1L;

            @Override
            protected void paintComponent(Graphics g) {
                super.paintComponent(g);
                g.setColor(Color.red);
                g.fillRect(0, 0, getWidth(), getHeight());
            }
        };
        panel.add(new JLabel("Very long textxxxxxxxxxxxxxxxxxxxxx "));
        add(panel);
        final JPopupMenu popupMenu = new JPopupMenu();
        m_mniInsertRow = new JMenuItem("Insert a Row");
        m_mniInsertRow.setOpaque(false);
        m_mniInsertScrip = new JMenuItem("Insert a Scrip");
        m_mniInsertScrip.setOpaque(false);
        m_mniDeleterRow = new JMenuItem("Delete a Row");
        m_mniDeleterRow.setOpaque(false);
        m_mniDeleteExpiredScrip = new JMenuItem("Delete a Expired Scrip");
        m_mniDeleteExpiredScrip.setOpaque(false);
        m_mniSetAlert = new JMenuItem("Set Alert");
        m_mniSetAlert.setOpaque(false);
        popupMenu.add(m_mniInsertRow);
        popupMenu.add(m_mniInsertScrip);
        popupMenu.addSeparator();
        popupMenu.add(m_mniDeleterRow);
        popupMenu.add(m_mniDeleteExpiredScrip);
        popupMenu.add(new JSeparator());
        popupMenu.add(m_mniSetAlert);
        panel.addMouseListener(new MouseAdapter() {

            @Override
            public void mouseReleased(MouseEvent e) {
                if (e.isPopupTrigger()) {
                    int x = e.getX();
                    int y = e.getY();
                    popupMenu.show(e.getComponent(), x, y);
                }
            }
        });
        setSize(new Dimension(400, 300));
        setLocationRelativeTo(null);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }

    public static void main(String[] args) {
        JFrame.setDefaultLookAndFeelDecorated(true);
        SwingUtilities.invokeLater(new Runnable() {

            @Override
            public void run() {
                Window w = new TranslucentWindow();
                w.setVisible(true);
                com.sun.awt.AWTUtilities.setWindowOpacity(w, 0.7f);
            }
        });
    }
}

EDIT

interesting support for Translucency and Nimbus L&F, especially Painter reproducing quite correct Color (Gradiend too on movement over the screen), ligth version with important changes for JPopupMenu, still from Java6

image

from code

import com.sun.java.swing.Painter;
import java.awt.*;
import javax.swing.*;

public class TranslucentWindow extends JFrame {

    private static final long serialVersionUID = 1L;
    private JPopupMenu popupMenu = new JPopupMenu();
    private JMenuItem m_mniInsertRow = new JMenuItem("Insert a Row");
    private JMenuItem m_mniInsertScrip = new JMenuItem("Delete a Row");
    private JMenuItem m_mniDeleterRow = new JMenuItem("Insert a Scrip");
    private JMenuItem m_mniDeleteExpiredScrip = new JMenuItem("Delete a Expired Scrip");
    private JMenuItem m_mniSetAlert = new JMenuItem("Set Alert");

    public TranslucentWindow() {
        super("Test translucent window");
        setLayout(new FlowLayout());
        add(new JButton("test"));
        add(new JCheckBox("test"));
        add(new JRadioButton("test"));
        add(new JProgressBar(0, 100));
        JPanel panel = new JPanel() {

            @Override
            public Dimension getPreferredSize() {
                return new Dimension(400, 300);
            }
            private static final long serialVersionUID = 1L;

            @Override
            protected void paintComponent(Graphics g) {
                super.paintComponent(g);
                g.setColor(Color.red);
                g.fillRect(0, 0, getWidth(), getHeight());
            }
        };
        panel.add(new JLabel("Very long textxxxxxxxxxxxxxxxxxxxxx "));
        panel.setComponentPopupMenu(popupMenu);
        add(panel);
        m_mniInsertRow.setOpaque(false);
        m_mniInsertScrip.setOpaque(false);
        m_mniDeleterRow.setOpaque(false);
        m_mniDeleteExpiredScrip.setOpaque(false);
        m_mniSetAlert.setOpaque(false);
        popupMenu.add(m_mniInsertRow);
        popupMenu.add(m_mniInsertScrip);
        popupMenu.addSeparator();
        popupMenu.add(m_mniDeleterRow);
        popupMenu.add(m_mniDeleteExpiredScrip);
        popupMenu.add(new JSeparator());
        popupMenu.add(m_mniSetAlert);
        setSize(new Dimension(400, 300));
        setLocationRelativeTo(null);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }

    public static void main(String[] args) {
        try {
            for (UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
                if ("Nimbus".equals(info.getName())) {
                    UIManager.setLookAndFeel(info.getClassName());
                    UIManager.getLookAndFeelDefaults().put("nimbusOrange", (new Color(127, 255, 191)));
                    UIManager.getLookAndFeelDefaults().put("PopupMenu[Enabled].backgroundPainter",
                            new FillPainter(new Color(127, 255, 191)));

                    break;
                }
            }
        } catch (ClassNotFoundException ex) {
        } catch (InstantiationException ex) {
        } catch (IllegalAccessException ex) {
        } catch (javax.swing.UnsupportedLookAndFeelException ex) {
        }
        SwingUtilities.invokeLater(new Runnable() {

            @Override
            public void run() {
                Window w = new TranslucentWindow();
                w.setVisible(true);
                com.sun.awt.AWTUtilities.setWindowOpacity(w, 0.7f);
            }
        });
    }

    static class FillPainter implements Painter<JComponent> {

        private final Color color;

        FillPainter(Color c) {
            color = c;
        }

        @Override
        public void paint(Graphics2D g, JComponent object, int width, int height) {
            g.setColor(color);
            g.fillRect(0, 0, width - 1, height - 1);
        }
    }
}

You don't have to extend JPopupMenu class, just make your menu non-opaque and then make the JMenuItems transparent instead (and non-opaque).

public class CustomMenuItem extends JMenuItem {
        public void paint(Graphics g) { 
                Graphics2D g2d = (Graphics2D) g.create(); 
                g2d.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_OVER, 0.2f)); 
                super.paint(g2d); 
                g2d.dispose(); 
        } 
}

OR, do the opposite, extend JPopupMenu to make it transparent and keep both the menu and items non-opaque (this way there will be no opaque border of the menu like above).

EDIT:

Note that (unfortunately) it does not work when the popup menu exceeds the frame bounds, as @Durandal remarked.

Though you could try to make some calculations and change location of popup (when needed) to keep it always inside the frame.

See this excellent 2008 article Translucent and Shaped Swing Windows by Kirill Grouchnikov.

Based on examples given in the above article and code borrowed from the JGoodies project, you can install a custom popup Look & Feel using the following 2 classes:

TranslucentPopup is the customized Popup, used by JPopupMenu:

/**
 * Translucent Popup
 *
 * @author Kirill Grouchnikov [https://www.java.net/pub/au/275]
 */
public class TranslucentPopup extends Popup {
    final JWindow popupWindow;

    TranslucentPopup(Component contents, int ownerX, int ownerY) {
        // create a new heavyweight window
        popupWindow = new JWindow();
        // mark the popup with partial opacity
        com.sun.awt.AWTUtilities.setWindowOpacity(popupWindow, 0.7f);
        // determine the popup location
        popupWindow.setLocation(ownerX, ownerY);
        // add the contents to the popup
        popupWindow.getContentPane().add(contents, BorderLayout.CENTER);
        contents.invalidate();
        JComponent parent = (JComponent) contents.getParent();
        // set a custom border
        parent.setBorder(BorderFactory.createRaisedSoftBevelBorder());
    }

    public void show() {
        popupWindow.setVisible(true);
        popupWindow.pack();
        // mark the window as non-opaque, so that the
        // border pixels take on the per-pixel opacity
        com.sun.awt.AWTUtilities.setWindowOpaque(popupWindow, false);
    }

    public void hide() {
        popupWindow.setVisible(false);
    }
}

TranslucentPopupFactory is requried to install the custom Look and Feel:

/**
 * Translucent Popup Factory
 *
 * @author Kirill Grouchnikov [https://www.java.net/pub/au/275]
 * @author Karsten Lentzsch (JGoodies project)
 */
public class TranslucentPopupFactory extends PopupFactory {
    /**
     * The PopupFactory used before this PopupFactory has been installed in
     * {@code #install}. Used to restored the original state in
     * {@code #uninstall}.
     */
    protected final PopupFactory storedFactory;

    protected TranslucentPopupFactory(PopupFactory originalFactory) {
        storedFactory = originalFactory;
    }

    public Popup getPopup(Component owner, Component contents, int x, int y) throws IllegalArgumentException {
        // A more complete implementation would cache and reuse popups
        return new TranslucentPopup(contents, x, y);
    }

    /**
      * Utility method to install the custom Popup Look and feel.
      * Call this method once during your application start-up.
      *
      * @author Karsten Lentzsch (JGoodies project)
      */
    public static void install() {
        PopupFactory factory = PopupFactory.getSharedInstance();
        if (factory instanceof TranslucentPopupFactory) {
            return;
        }

        PopupFactory.setSharedInstance(new TranslucentPopupFactory(factory));
    }

    /**
      * Utility method to uninstall the custom Popup Look and feel
      * @author Karsten Lentzsch (JGoodies project)
      */
    public static void uninstall() {
        PopupFactory factory = PopupFactory.getSharedInstance();
        if (!(factory instanceof TranslucentPopupFactory)) {
            return;
        }

        PopupFactory stored = ((TranslucentPopupFactory) factory).storedFactory;
        PopupFactory.setSharedInstance(stored);
    }
}

The result is that all Popups (including JPopupMenu and perhaps also ToolTips) will now be Translucent, and optionally have a custom border:

来源：https://stackoverflow.com/questions/12801035/how-can-i-make-a-jpopupmenu-transparent

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