JPopupMenu删除背景和边框

Question

JPopupMenu http://s010.radikal.ru/i313/1209/25/2213e2145879.gif

我需要删除的背景和Border在JPopupMenu.JPopupMenu应该是完全透明的.覆盖paintComponent不会给出积极的结果.我也尝试在BasicMenuItemUI/ PopupMenuUI和MenuItemUI/中找到解决方案,BasicPopupMenuUI但发现渲染背景和边框不在其中.

public class CustomMenuItemUI extends BasicMenuItemUI {
    protected MouseInputListener mouseInputListener;
    protected MenuDragMouseListener menuDragMouseListener;
    public static ComponentUI createUI(JComponent c) {
        return new CustomMenuItemUI();
    }

    private static float alpha = 0.0f;
    private static float selectionAlpha = 0.0f;

    public static float getAlpha() {
        return alpha;
    }

    public static void setAlpha(float _alpha) {
        alpha = _alpha;
    }

    @Override
    public void installUI(JComponent c) {
        super.installUI(c);
        menuItem.setOpaque(false);
    }

    @Override
    public void paint(Graphics g, JComponent comp) {
        Graphics2D gx = (Graphics2D) g.create();
        gx.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_OVER, alpha));
        super.paint(gx, comp);
        gx.dispose();
    }

    @Override
    protected void paintBackground(Graphics g, JMenuItem menuItem, Color bgColor) {
        ButtonModel model = menuItem.getModel();
        Color oldColor = Color.red;
        int menuWidth = menuItem.getWidth();
        int menuHeight = menuItem.getHeight();
        if (model.isArmed() || (menuItem instanceof JMenu && model.isSelected())) {
            Graphics2D g2 = (Graphics2D) g.create(); 
            g2.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_OVER, selectionAlpha));
            g2.setColor(Color.red);
            g2.fillRect(0, 0, menuWidth, menuHeight);
        } else {
            g.setColor(Color.red);
            g.fillRect(0, 0, menuWidth, menuHeight);
        }
        g.setColor(oldColor);
    }

    @Override
    protected void paintText(Graphics g, JMenuItem menuItem, Rectangle textRect, String text) {
        ButtonModel model = menuItem.getModel();
        if (model.isArmed() || model.isSelected() || !model.isSelected()) {
            Graphics2D g2 = (Graphics2D) g.create();
            g2.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_OVER, 1.0f));
            super.paintText(g2, menuItem, textRect, text);
            g2.dispose();
        } else {
            super.paintText(g, menuItem, textRect, text);
        }
    }
    public static void setSelectionAlpha(float alpha) {
        selectionAlpha  = alpha;
    }
}

---

    String poppUI = CustomPopupMenuUI.class.getName(); 
UIManager.put("PopupMenuUI", poppUI);

Answer 1

您可以更改PopupMenuUI委托的属性,但不能保证您选择的外观和服务将遵循更改.在实例化任何GUI组件之前,更改应该在程序的早期.

UIManager.put("PopupMenu.background", new Color(0));
UIManager.put("PopupMenu.border", BorderFactory.createEmptyBorder());

附录:正如@MadProgrammer评论的那样,平台的对等组件可能是不透明的,并且无法控制.您的代码(MenuTest,CustomPopupMenuUI,CustomMenuItemUI),低于上显示的外观com.apple.laf.AquaLookAndFeel.在缺乏一个更好的解决方案,你可能看如图所示实现自己的半透明窗口在这里.