JScrollMenu.java

package net.sf.jailer.ui.scrollmenu;

import javax.swing.Action;
import javax.swing.JButton;
import javax.swing.JMenu;
import javax.swing.JMenuItem;
import javax.swing.JPopupMenu;
import javax.swing.MenuElement;
import javax.swing.UIManager;
import javax.swing.plaf.MenuItemUI;
import javax.swing.plaf.PopupMenuUI;
import java.awt.Component;
import java.awt.ComponentOrientation;

/**
 * http://stackoverflow.com/questions/9288350/adding-vertical-scroll-to-a-jpopupmenu
 */
public class JScrollMenu extends JMenu {
	// Covers the one in the JMenu because the method that creates it in JMenu
	// is private
	/** The popup menu portion of the menu. */
	private JPopupMenu popupMenu;

	/**
	 * Constructs a new <code>JMenu</code> with no text.
	 */
	public JScrollMenu() {
		this("");
	}

	/**
	 * Constructs a new <code>JMenu</code> with the supplied string as its text.
	 * 
	 * @param s
	 *            the text for the menu label
	 */
	public JScrollMenu(String s) {
		super(s);
	}

	/**
	 * Constructs a menu whose properties are taken from the <code>Action</code>
	 * supplied.
	 * 
	 * @param a
	 *            an <code>Action</code>
	 */
	public JScrollMenu(Action a) {
		this();
		setAction(a);
	}

	/**
	 * Lazily creates the popup menu. This method will create the popup using
	 * the <code>JScrollPopupMenu</code> class.
	 */
	protected void ensurePopupMenuCreated() {
		if (popupMenu == null) {
			this.popupMenu = new JScrollPopupMenu();
			popupMenu.setInvoker(this);
			popupListener = createWinListener(popupMenu);
		}
	}

	// ////////////////////////////
	// // All of these methods are necessary because ensurePopupMenuCreated() is
	// private in JMenu
	// ////////////////////////////
	@Override
	public void updateUI() {
		setUI((MenuItemUI) UIManager.getUI(this));

		if (popupMenu != null) {
			popupMenu.setUI((PopupMenuUI) UIManager.getUI(popupMenu));
		}
	}

	@Override
	public boolean isPopupMenuVisible() {
		ensurePopupMenuCreated();
		return popupMenu.isVisible();
	}

	@Override
	public void setMenuLocation(int x, int y) {
		super.setMenuLocation(x, y);
		if (popupMenu != null) {
			popupMenu.setLocation(x, y);
		}
	}

	@Override
	public JMenuItem add(JMenuItem menuItem) {
		ensurePopupMenuCreated();
		return popupMenu.add(menuItem);
	}

	@Override
	public Component add(Component c) {
		ensurePopupMenuCreated();
		popupMenu.add(c);
		return c;
	}

	@Override
	public Component add(Component c, int index) {
		ensurePopupMenuCreated();
		popupMenu.add(c, index);
		return c;
	}

	@Override
	public void addSeparator() {
		ensurePopupMenuCreated();
		popupMenu.addSeparator();
	}

	@Override
	public void insert(String s, int pos) {
		if (pos < 0) {
			throw new IllegalArgumentException("index less than zero.");
		}

		ensurePopupMenuCreated();
		popupMenu.insert(new JMenuItem(s), pos);
	}

	@Override
	public JMenuItem insert(JMenuItem mi, int pos) {
		if (pos < 0) {
			throw new IllegalArgumentException("index less than zero.");
		}
		ensurePopupMenuCreated();
		popupMenu.insert(mi, pos);
		return mi;
	}

	@Override
	public JMenuItem insert(Action a, int pos) {
		if (pos < 0) {
			throw new IllegalArgumentException("index less than zero.");
		}

		ensurePopupMenuCreated();
		JMenuItem mi = new JMenuItem(a);
		mi.setHorizontalTextPosition(JButton.TRAILING);
		mi.setVerticalTextPosition(JButton.CENTER);
		popupMenu.insert(mi, pos);
		return mi;
	}

	@Override
	public void insertSeparator(int index) {
		if (index < 0) {
			throw new IllegalArgumentException("index less than zero.");
		}

		ensurePopupMenuCreated();
		popupMenu.insert(new JPopupMenu.Separator(), index);
	}

	@Override
	public void remove(JMenuItem item) {
		if (popupMenu != null) {
			popupMenu.remove(item);
		}
	}

	@Override
	public void remove(int pos) {
		if (pos < 0) {
			throw new IllegalArgumentException("index less than zero.");
		}
		if (pos > getItemCount()) {
			throw new IllegalArgumentException(
					"index greater than the number of items.");
		}
		if (popupMenu != null) {
			popupMenu.remove(pos);
		}
	}

	@Override
	public void remove(Component c) {
		if (popupMenu != null) {
			popupMenu.remove(c);
		}
	}

	@Override
	public void removeAll() {
		if (popupMenu != null) {
			popupMenu.removeAll();
		}
	}

	@Override
	public int getMenuComponentCount() {
		return (popupMenu == null) ? 0 : popupMenu.getComponentCount();
	}

	@Override
	public Component getMenuComponent(int n) {
		return (popupMenu == null) ? null : popupMenu.getComponent(n);
	}

	@Override
	public Component[] getMenuComponents() {
		return (popupMenu == null) ? new Component[0] : popupMenu
				.getComponents();
	}

	@Override
	public JPopupMenu getPopupMenu() {
		ensurePopupMenuCreated();
		return popupMenu;
	}

	@Override
	public MenuElement[] getSubElements() {
		return popupMenu == null ? new MenuElement[0]
				: new MenuElement[] { popupMenu };
	}

	@Override
	public void applyComponentOrientation(ComponentOrientation o) {
		super.applyComponentOrientation(o);

		if (popupMenu != null) {
			int ncomponents = getMenuComponentCount();
			for (int i = 0; i < ncomponents; ++i) {
				getMenuComponent(i).applyComponentOrientation(o);
			}
			popupMenu.setComponentOrientation(o);
		}
	}

	@Override
	public void setComponentOrientation(ComponentOrientation o) {
		super.setComponentOrientation(o);
		if (popupMenu != null) {
			popupMenu.setComponentOrientation(o);
		}
	}
}