PopupMenu


1   /*
2    * @(#)PopupMenu.java   1.29 04/03/16
3    *
4    * Copyright 2004 Sun Microsystems, Inc. All rights reserved.
5    * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
6    */
7   
8   package java.awt;
9   
10  import java.awt.peer.PopupMenuPeer;
11  import javax.accessibility.*;
12  
13  
14  /**
15   * A class that implements a menu which can be dynamically popped up
16   * at a specified position within a component.
17   * <p>
18   * As the inheritance hierarchy implies, a <code>PopupMenu</code>
19   *  can be used anywhere a <code>Menu</code> can be used.
20   * However, if you use a <code>PopupMenu</code> like a <code>Menu</code>
21   * (e.g., you add it to a <code>MenuBar</code>), then you <b>cannot</b>
22   * call <code>show</code> on that <code>PopupMenu</code>.
23   *
24   * @version 1.29 03/16/04
25   * @author  Amy Fowler
26   */
27  public class PopupMenu extends Menu   {
28  
29      private static final String   base = "popup";
30      static int nameCounter = 0;
31  
32      /*
33       * JDK 1.1 serialVersionUID
34       */
35      private static final long serialVersionUID = -4620452533522760060L;
36  
37      /**
38       * Creates a new popup menu with an empty name.
39       * @exception HeadlessException if GraphicsEnvironment.isHeadless()
40       * returns true.
41       * @see java.awt.GraphicsEnvironment#isHeadless
42       */
43      public PopupMenu() throws HeadlessException   {
44      this("");
45      }
46  
47      /**
48       * Creates a new popup menu with the specified name.
49       *
50       * @param label a non-<code>null</code> string specifying
51       *                the popup menu's label 
52       * @exception HeadlessException if GraphicsEnvironment.isHeadless()
53       * returns true.
54       * @see java.awt.GraphicsEnvironment#isHeadless
55       */
56      public PopupMenu(String   label) throws HeadlessException   {
57      super(label);
58      }
59  
60      /**
61       * Constructs a name for this <code>MenuComponent</code>.
62       * Called by <code>getName</code> when the name is <code>null</code>.
63       */
64      String   constructComponentName() {
65          synchronized (getClass()) {
66          return base + nameCounter++;
67      }
68      }
69  
70      /**
71       * Creates the popup menu's peer.
72       * The peer allows us to change the appearance of the popup menu without
73       * changing any of the popup menu's functionality.
74       */
75      public void addNotify() {
76          synchronized (getTreeLock()) {
77          // If our parent is not a Component, then this PopupMenu is
78          // really just a plain, old Menu.
79          if (parent != null && !(parent instanceof Component  )) {
80              super.addNotify();
81          }
82          else {
83              if (peer == null)
84              peer = Toolkit.getDefaultToolkit().createPopupMenu(this);
85          int nitems = getItemCount();
86          for (int i = 0 ; i < nitems ; i++) {
87              MenuItem   mi = getItem(i);
88              mi.parent = this;
89              mi.addNotify();
90          }
91          }
92      }
93      }
94  
95     /**
96       * Shows the popup menu at the x, y position relative to an origin
97       * component.
98       * The origin component must be contained within the component
99       * hierarchy of the popup menu's parent.  Both the origin and the parent 
100      * must be showing on the screen for this method to be valid.
101      * <p>
102      * If this <code>PopupMenu</code> is being used as a <code>Menu</code>
103      * (i.e., it has a non-<code>Component</code> parent),
104      * then you cannot call this method on the <code>PopupMenu</code>.
105      * 
106      * @param origin the component which defines the coordinate space
107      * @param x the x coordinate position to popup the menu
108      * @param y the y coordinate position to popup the menu
109      * @exception NullPointerException  if the parent is <code>null</code>
110      * @exception IllegalArgumentException  if this <code>PopupMenu</code>
111      *                has a non-<code>Component</code> parent
112      * @exception IllegalArgumentException if the origin is not in the
113      *                parent's heirarchy
114      * @exception RuntimeException if the parent is not showing on screen
115      */
116     public void show(Component   origin, int x, int y) {
117         // Use localParent for thread safety.
118         MenuContainer   localParent = parent;
119     if (localParent == null) {
120         throw new NullPointerException  ("parent is null");
121     }
122         if (!(localParent instanceof Component  )) {
123         throw new IllegalArgumentException  (
124             "PopupMenus with non-Component parents cannot be shown");
125     }
126         Component   compParent = (Component  )localParent;
127     if (compParent != origin &&
128         compParent instanceof Container   &&
129         !((Container  )compParent).isAncestorOf(origin)) {
130             throw new IllegalArgumentException  (
131             "origin not in parent's hierarchy");
132     }
133     if (compParent.getPeer() == null || !compParent.isShowing()) {
134         throw new RuntimeException  ("parent not showing on screen");
135     }
136     if (peer == null) {
137         addNotify();
138     }
139     synchronized (getTreeLock()) {
140         if (peer != null) {
141             ((PopupMenuPeer)peer).show(
142             new Event  (origin, 0, Event.MOUSE_DOWN, x, y, 0, 0));
143         }
144     }
145     }
146 
147 
148 /////////////////
149 // Accessibility support
150 ////////////////
151 
152     /**
153      * Gets the <code>AccessibleContext</code> associated with this
154      * <code>PopupMenu</code>.
155      *
156      * @return the <code>AccessibleContext</code> of this
157      *                <code>PopupMenu</code>
158      */
159     public AccessibleContext getAccessibleContext() {
160         if (accessibleContext == null) {
161             accessibleContext = new AccessibleAWTPopupMenu();
162         }
163         return accessibleContext;
164     }
165 
166     /**
167      * Inner class of PopupMenu used to provide default support for
168      * accessibility.  This class is not meant to be used directly by
169      * application developers, but is instead meant only to be
170      * subclassed by menu component developers.
171      * <p>
172      * The class used to obtain the accessible role for this object.
173      */
174     protected class AccessibleAWTPopupMenu extends AccessibleAWTMenu
175     {
176         /*
177          * JDK 1.3 serialVersionUID
178          */
179         private static final long serialVersionUID = -4282044795947239955L;
180 
181         /**
182          * Get the role of this object.
183          *
184          * @return an instance of AccessibleRole describing the role of the 
185          * object
186          */
187         public AccessibleRole getAccessibleRole() {
188             return AccessibleRole.POPUP_MENU;
189         }
190 
191     } // class AccessibleAWTPopupMenu
192 
193 }
194
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