popupmenu.java

《移动Agent技术》一书的所有章节源代码。

/*
 * @(#)PopupMenu.java	1.13 98/08/21
 *
 * Copyright 1995-1998 by Sun Microsystems, Inc.,
 * 901 San Antonio Road, Palo Alto, California, 94303, U.S.A.
 * All rights reserved.
 *
 * This software is the confidential and proprietary information
 * of Sun Microsystems, Inc. ("Confidential Information").  You
 * shall not disclose such Confidential Information and shall use
 * it only in accordance with the terms of the license agreement
 * you entered into with Sun.
 */

package java.awt;

import java.awt.peer.PopupMenuPeer;


/**
 * A class that implements a menu which can be dynamically popped up
 * at a specified position within a component.
 *
 * @version	1.13 08/21/98
 * @author 	Amy Fowler
 */
public class PopupMenu extends Menu {

    private static final String base = "popup";
    static int nameCounter = 0;

    /*
     * JDK 1.1 serialVersionUID
     */
    private static final long serialVersionUID = -4620452533522760060L;

    /**
     * Creates a new popup menu.
     */
    public PopupMenu() {
	this("");
    }

    /**
     * Creates a new popup menu with the specified name.
     * @param title the title string for the popup menu
     */
    public PopupMenu(String label) {
	super(label);
    }

    /**
     * Construct a name for this MenuComponent.  Called by getName() when
     * the name is null.
     */
    String constructComponentName() {
	return base + nameCounter++;
    }

    /**
     * Creates the popup menu's peer.  The peer allows us to change the
     * appearance of the popup menu without changing any of the popup menu's
     * functionality.
     */
    public void addNotify() {
      synchronized (getTreeLock()) {
	if (peer == null) {
	    peer = Toolkit.getDefaultToolkit().createPopupMenu(this);
	}
	int nitems = getItemCount();
	for (int i = 0 ; i < nitems ; i++) {
	    MenuItem mi = getItem(i);
	    mi.parent = this;
	    mi.addNotify();
	}
      }
    }

   /**
     * Shows the popup menu at the x, y position relative to an origin component.
     * The origin component must be contained within the component hierarchy
     * of the popup menu's parent.  Both the origin and the parent must be
     * showing on the screen for this method to be valid.
     * @param origin the component which defines the coordinate space
     * @param x the x coordinate position to popup the menu
     * @param y the y coordinate position to popup the menu
     */
    public void show(Component origin, int x, int y) {
	Component p = (Component)parent;
	if (p == null) {
	    throw new NullPointerException("parent is null");
	}
	if (p != origin &&
	    p instanceof Container && !((Container)p).isAncestorOf(origin)) {
	    throw new IllegalArgumentException("origin not in parent's hierarchy");
	}
	if (p.getPeer() == null || !p.isShowing()) {
	    throw new RuntimeException("parent not showing on screen");
	}
	if (peer == null) {
	    addNotify();
	}
        synchronized (getTreeLock()) {
            if (peer != null) {
                ((PopupMenuPeer)peer).show(
                    new Event(origin, 0, Event.MOUSE_DOWN, x, y, 0, 0));
            }
        }
    }
}