扩展JMenuItem (SplitMenuItem)

Question

单击SplitMenuItem的行为与任何其他常规JMenuItem一样。但是SplitMenuItem的右侧有一个额外的向下箭头，当单击该箭头时，将出现一个JComboBox类似下拉菜单，您可以从中选择进一步的操作。此功能通常是在应用子菜单时实现的。SplitMenuItem的思想来源于这样一种情况，即在频率上有一个主要的动作，而其他一些与该主要动作相关的动作却很少被选择。对于SplitMenuItem，这个主要操作总是可以直接访问的，因为子菜单的打开已经变得不必要了。我使用了@MadProgrammer的SplitButton中的代码，并将其修改为JMenuItem，但仍然不能接受的是：

• flicker
• unusual行为SplitMenuItem的弹出displayed.

1. 在
2. 上没有在鼠标上突出显示项目取消或关闭项是强制性的，因为弹出窗口在“外部”单击时没有关闭。
3. 父菜单完全正常，而弹出窗口是displayed.

。

到目前为止我尝试过的是：

将所有listeners

• Attaching a FocusListener (focusLost)移除给SplitMenuItem的父级(即JPopupMenu)。它不会被触发。

为了让MCV运行，我封装了大部分SplitMenuItem类。但实际上，除了将JButton更改为JMenuItem之外，实际上只修改了一个参数构造函数和方法showPopupMenu()。

/**
 * A JMenuItem that has an additional section with an arrow icon on the right 
 * that when clicked shows a JPopupMenu that is positioned flush with the
 * menu item.
 * 
 * Credit:
 * An adaptation of SplitButton finalized by MadProgrammer and DUDSS.
 * https://stackoverflow.com/questions/36352707/actions-inside-of-another-action-like-netbeans
 * Applying code from Darryl Burke's StayOpenMenuItem.
 * https://tips4java.wordpress.com/2010/09/12/keeping-menus-open/
 *
*/

import java.awt.*;
import java.awt.event.*;
import java.awt.image.*;
import java.beans.*;
import javax.swing.*;
import javax.swing.event.*;

public class SplitMenuItem extends JMenuItem {
    private int separatorSpacing = 4;
    private int splitWidth = 22;
    private int arrowSize = 8;
    private boolean onSplit;
    private Rectangle splitRectangle;
    private boolean alwaysDropDown;
    private Color arrowColor = Color.BLACK;
    private Color disabledArrowColor = Color.GRAY;
    private Image image;
    private MouseHandler mouseHandler;

    private JPopupMenu jpopupMenu;

//  From Darryl Burke's StayOpenMenuItem.
    private static MenuElement[] path;

    {
      getModel().addChangeListener(new ChangeListener() {

        @Override
        public void stateChanged(ChangeEvent e) {
          if (getModel().isArmed() && isShowing()) {
            path = MenuSelectionManager.defaultManager().getSelectedPath();
          }
        }
      });
    }


    public SplitMenuItem(JMenu parent) {
        super();
        addMouseMotionListener(getMouseHandler());
        addMouseListener(getMouseHandler());
        // Default for no "default" action...
        setAlwaysDropDown(true);
//      The next line prevents the JMenu's item list/JPopupMenu to become
//      invisible when clicking on SplitMenuItem's arrow.
        setUI(new StayOpenMenuItemUI());

        InputMap im = getInputMap(WHEN_FOCUSED);
        im.put(KeyStroke.getKeyStroke(KeyEvent.VK_ESCAPE, 0),
                                                        "PopupMenu.close");
        ActionMap am = getActionMap();
        am.put("PopupMenu.close", new ClosePopupAction());
        JPopupMenu parentPop= parent.getPopupMenu();
/*      Never fired.
        parentPop.addFocusListener(new FocusAdapter() {
            public void focusLost(FocusEvent e) {
                DBG.p("ParentMenu lost focus");
            }
        });
*/
        parentPop.addPopupMenuListener(new PopupMenuListener() {
            public void popupMenuCanceled(PopupMenuEvent e) {
            }

            public void popupMenuWillBecomeInvisible(PopupMenuEvent e) {
//              This method is called before any actionPerformed in child-popup.
                Timer t = new javax.swing.Timer(0, new ActionListener() {
                  public void actionPerformed(ActionEvent e) {
                    if (jpopupMenu.isVisible())
                    MenuSelectionManager.defaultManager().setSelectedPath(path);
                  }
                });
                t.setRepeats(false);
                t.start();
            }

            public void popupMenuWillBecomeVisible(PopupMenuEvent e) {
            }
        });
    }

    public SplitMenuItem(JMenu parent, String text) {
        this(parent);
        setText(text);
    }

    public SplitMenuItem(JMenu parent, String text, JPopupMenu popup) {
        this(parent);
        setText(text);
        setPopupMenu(popup);
    }

    @Override
    public void addActionListener(ActionListener l) {
        if (l != null) {
             setAlwaysDropDown(false);
        }
        super.addActionListener(l);
    }

    protected void closePopupMenu() {
        getPopupMenu().setVisible(false);
    }

    @Override
    protected void fireActionPerformed(ActionEvent event) {
        // This is a little bit of a nasty trick.  Basically this is where
        // we try and decide if the menuItems "default" action should
        // be fired or not.  We don't want it firing if the menuItem
        // is in "options only" mode or the user clicked on the
        // "drop down arrow".
        if (onSplit || isAlwaysDropDown()) {
            showPopupMenu();
        } else {
            super.fireActionPerformed(event);
        }
    }

    /**
     * Gets the image to be drawn in the split part. If no is set, a new image
     * is created with the triangle.
     *
     * @return image
     */
    public Image getImage() {
        if (image == null) {
            Graphics2D g = null;
            BufferedImage img = new BufferedImage(arrowSize, arrowSize,
                                                  BufferedImage.TYPE_INT_RGB);
            g = (Graphics2D) img.createGraphics();
            g.setColor(Color.WHITE);
            g.fillRect(0, 0, img.getWidth(), img.getHeight());
            g.setColor(jpopupMenu != null ? arrowColor : disabledArrowColor);
            //this creates a triangle facing right >
            g.fillPolygon(new int[]{0, 0, arrowSize/2},
                          new int[]{0, arrowSize, arrowSize/2}, 3);
            g.dispose();
            //rotate it to face downwards
            img = rotate(img, 90);
            BufferedImage dimg = new BufferedImage(img.getWidth(),
                                  img.getHeight(), BufferedImage.TYPE_INT_ARGB);
            g = (Graphics2D) dimg.createGraphics();
            g.setComposite(AlphaComposite.Src);
            g.drawImage(img, null, 0, 0);
            g.dispose();
            for (int i = 0; i < dimg.getHeight(); i++) {
                for (int j = 0; j < dimg.getWidth(); j++) {
                    if (dimg.getRGB(j, i) == Color.WHITE.getRGB()) {
                        dimg.setRGB(j, i, 0x8F1C1C);
                    }
                }
            }

            image = Toolkit.getDefaultToolkit().createImage(dimg.getSource());
        }
        return image;
    }

    @Override
    public Insets getInsets() {
        Insets insets = (Insets) super.getInsets().clone();
        insets.right += splitWidth;
        return insets;
    }

    @Override
    public Insets getInsets(Insets insets) {
        Insets insets1 = getInsets();
        insets.left = insets1.left;
        insets.right = insets1.right;
        insets.bottom = insets1.bottom;
        insets.top = insets1.top;
        return insets1;
    }

    protected MouseHandler getMouseHandler() {
        if (mouseHandler == null) {
            mouseHandler = new MouseHandler();
        }
        return mouseHandler;
    }

    protected int getOptionsCount() {
        return getPopupMenu().getComponentCount();
    }

    /**
     * Returns the menuItems popup menu.
     *
     * @return
     */
    public JPopupMenu getPopupMenu() {
        if (jpopupMenu == null) {
            jpopupMenu = new JPopupMenu();
        }
        return jpopupMenu;
    }

    /**
     *Show the dropdown menu, if attached, even if the menuItem part is clicked.
     *
     * @return true if alwaysDropdown, false otherwise.
     */
    public boolean isAlwaysDropDown() {
        return alwaysDropDown;
    }

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        //Graphics gClone = g.create();//EDIT: Hervé Guillaume
        Color oldColor = g.getColor();
        splitRectangle = new Rectangle(getWidth() - splitWidth, 0, splitWidth,
                                        getHeight());
        g.translate(splitRectangle.x, splitRectangle.y);
        int mh = getHeight() / 2;
        int mw = splitWidth / 2;
        g.drawImage(getImage(), mw-arrowSize/2, mh+2 - arrowSize/2, null);
        if (!alwaysDropDown) {
            if (getModel().isRollover() || isFocusable()) {
                g.setColor(UIManager.getLookAndFeelDefaults()
                        .getColor("MenuItem.background"));
                g.drawLine(1, separatorSpacing + 2, 1,
                        getHeight() - separatorSpacing - 2);
                g.setColor(UIManager.getLookAndFeelDefaults()
                        .getColor("MenuItem.shadow"));
                g.drawLine(2, separatorSpacing + 2, 2,
                        getHeight() - separatorSpacing - 2);
            }
        }
        g.setColor(oldColor);
        g.translate(-splitRectangle.x, -splitRectangle.y);
    }

    /**
     * Rotates the given image with the specified angle.
     *
     * @param img image to rotate
     * @param angle angle of rotation
     * @return rotated image
     */
    private BufferedImage rotate(BufferedImage img, int angle) {
        int w = img.getWidth();
        int h = img.getHeight();
        BufferedImage dimg = dimg = new BufferedImage(w, h, img.getType());
        Graphics2D g = dimg.createGraphics();
        g.rotate(Math.toRadians(angle), w / 2, h / 2);
        g.drawImage(img, null, 0, 0);
        return dimg;
    }

    /**
     *Show the dropdown menu, if attached, even if the menuItem part is clicked.
     *
     * If true, this will prevent the menuItem from raising any actionPerformed
     * events for itself.
     *
     * @param value true to show the attached dropdown even if the menuItem part
     * is clicked, false otherwise
     */
    public void setAlwaysDropDown(boolean value) {
        if (alwaysDropDown != value) {
            this.alwaysDropDown = value;
            firePropertyChange("alwaysDropDown", !alwaysDropDown,
                                                                alwaysDropDown);
        }
    }

    public void setPopupMenu(JPopupMenu popup) {
        jpopupMenu = popup;
        this.setComponentPopupMenu(popup);
    }


    protected void showPopupMenu() {
        if (getOptionsCount() > 0) {
            JPopupMenu popup = getPopupMenu();
            Point p= getLocationOnScreen();
            popup.setLocation(p.x+getWidth() - popup.getPreferredSize().width,
                              p.y+getHeight());
            popup.setVisible(true);
//            Must be showing on the screen to determine its location.
//            popup.show(this, (getWidth() - popup.getWidth()), getHeight());
        }
    }

/*
    private JMenu getMenu() {
      JMenu menu = null;
      while (menu == null) {
        JPopupMenu popup = (JPopupMenu)this.getParent();
        JMenuItem item = (JMenuItem)popup.getInvoker();
        if (!(item.getParent() instanceof JPopupMenu)) menu = (JMenu)item;
      }
      return menu;
    }
*/

    protected class ClosePopupAction extends AbstractAction {
        @Override
        public void actionPerformed(ActionEvent e) {
            closePopupMenu();
        }
    }

    protected class MouseHandler extends MouseAdapter {
        @Override
        public void mouseExited(MouseEvent e) {
            onSplit = false;
            repaint(splitRectangle);
        }

        @Override
        public void mouseMoved(MouseEvent e) {
            if (splitRectangle.contains(e.getPoint())) {
                onSplit = true;
            } else {
                onSplit = false;
            }
            repaint(splitRectangle);
        }
    }
}


/**************************************************************************/
import javax.swing.*;
import javax.swing.plaf.basic.*;

class StayOpenMenuItemUI extends BasicMenuItemUI {
 
  @Override
  protected void doClick(MenuSelectionManager msm) {
    menuItem.doClick(0);
  }
}


/**************************************************************************/
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class SplitMenuItemTest extends JFrame {
  public static final long serialVersionUID = 100L;
  JMenuItem exitItem, welcomeItem;
  SplitMenuItem splitItem;

  public SplitMenuItemTest() {
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    setSize(300, 240);
    setLocationRelativeTo(null);

    JMenuBar menuBar= new JMenuBar();
    setJMenuBar(menuBar);
    JMenu menu= new JMenu("A menu");
    menuBar.add(menu);

    welcomeItem= new JMenuItem("Welcome");
    ActListener actListener= new ActListener();
    welcomeItem.addActionListener(actListener);
    menu.add(welcomeItem);

    JPopupMenu popup= createPopupForItem();
    splitItem= new SplitMenuItem(menu, "Most often this", popup);
    splitItem.addActionListener(e -> {
      JOptionPane.showMessageDialog(SplitMenuItemTest.this,
        "The usual action of this menuItem will be performed.");
    });
    menu.add(splitItem);

    exitItem= new JMenuItem("Exit");
    exitItem.addActionListener(actListener);
    menu.add(exitItem);
    setVisible(true);
  }


  static public void main(String args[]) {
    EventQueue.invokeLater(SplitMenuItemTest::new);
  }


  private JPopupMenu createPopupForItem() {
    JPopupMenu popup= new JPopupMenu();
    JMenuItem seldomItem= popup.add("Seldomly used");
    seldomItem.addActionListener(e -> {
      System.out.println(seldomItem.getText());
      popup.setVisible(false);
    });
    JMenuItem rareTaskItem= popup.add("Rare task");
    rareTaskItem.addActionListener(e -> {
      System.out.println(rareTaskItem.getText());
      popup.setVisible(false);
    });
    popup.addSeparator();
    JMenuItem cancelItem= popup.add("Cancel"); // Mandatory JMenuItem.
    cancelItem.addActionListener(e -> {
      popup.setVisible(false);
    });
    return popup;
  }


  public class ActListener implements ActionListener {
    public void actionPerformed(ActionEvent e) {
      Object obj= e.getSource();
      if (obj==exitItem)
        System.exit(0);
      else if (obj==welcomeItem)
        System.out.println("Welcome");
      else
        System.out.println("SplitItem was clicked.");
    }
  }

}

Answer 1

如果使用带有JMenu派生类的子菜单，该类以水平线呈现(也可以用文本"More actions.“代替)如何？或者别的什么)？

那么您的导航问题就应该消失了，而外观和感觉仍然是一样的。