1 /*
   2  * Copyright (c) 1999, 2008, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 package java.awt.event;
  27 
  28 import java.awt.AWTEvent;
  29 import java.awt.Component;
  30 import java.awt.Container;
  31 
  32 /**
  33  * An event which indicates a change to the <code>Component</code>
  34  * hierarchy to which <code>Component</code> belongs.
  35  * <ul>
  36  * <li>Hierarchy Change Events (HierarchyListener)
  37  *     <ul>
  38  *     <li> addition of an ancestor
  39  *     <li> removal of an ancestor
  40  *     <li> hierarchy made displayable
  41  *     <li> hierarchy made undisplayable
  42  *     <li> hierarchy shown on the screen (both visible and displayable)
  43  *     <li> hierarchy hidden on the screen (either invisible or undisplayable)
  44  *     </ul>
  45  * <li>Ancestor Reshape Events (HierarchyBoundsListener)
  46  *     <ul>
  47  *     <li> an ancestor was resized
  48  *     <li> an ancestor was moved
  49  *     </ul>
  50  * </ul>
  51  * <p>
  52  * Hierarchy events are provided for notification purposes ONLY.
  53  * The AWT will automatically handle changes to the hierarchy internally so
  54  * that GUI layout and displayability works properly regardless of whether a
  55  * program is receiving these events or not.
  56  * <p>
  57  * This event is generated by a Container object (such as a Panel) when the
  58  * Container is added, removed, moved, or resized, and passed down the
  59  * hierarchy. It is also generated by a Component object when that object's
  60  * <code>addNotify</code>, <code>removeNotify</code>, <code>show</code>, or
  61  * <code>hide</code> method is called. The {@code ANCESTOR_MOVED} and
  62  * {@code ANCESTOR_RESIZED}
  63  * events are dispatched to every <code>HierarchyBoundsListener</code> or
  64  * <code>HierarchyBoundsAdapter</code> object which registered to receive
  65  * such events using the Component's <code>addHierarchyBoundsListener</code>
  66  * method. (<code>HierarchyBoundsAdapter</code> objects implement the <code>
  67  * HierarchyBoundsListener</code> interface.) The {@code HIERARCHY_CHANGED} events are
  68  * dispatched to every <code>HierarchyListener</code> object which registered
  69  * to receive such events using the Component's <code>addHierarchyListener
  70  * </code> method. Each such listener object gets this <code>HierarchyEvent
  71  * </code> when the event occurs.
  72  * <p>
  73  * An unspecified behavior will be caused if the {@code id} parameter
  74  * of any particular {@code HierarchyEvent} instance is not
  75  * in the range from {@code HIERARCHY_FIRST} to {@code HIERARCHY_LAST}.
  76  * <br>
  77  * The {@code changeFlags} parameter of any {@code HierarchyEvent} instance takes one of the following
  78  * values:
  79  * <ul>
  80  * <li> {@code HierarchyEvent.PARENT_CHANGED}
  81  * <li> {@code HierarchyEvent.DISPLAYABILITY_CHANGED}
  82  * <li> {@code HierarchyEvent.SHOWING_CHANGED}
  83  * </ul>
  84  * Assigning the value different from listed above will cause unspecified behavior.
  85  *
  86  * @author      David Mendenhall
  87  * @see         HierarchyListener
  88  * @see         HierarchyBoundsAdapter
  89  * @see         HierarchyBoundsListener
  90  * @since       1.3
  91  */
  92 public class HierarchyEvent extends AWTEvent {
  93     /*
  94      * serialVersionUID
  95      */
  96     private static final long serialVersionUID = -5337576970038043990L;
  97 
  98     /**
  99      * Marks the first integer id for the range of hierarchy event ids.
 100      */
 101     public static final int HIERARCHY_FIRST = 1400; // 1300 used by sun.awt.windows.ModalityEvent
 102 
 103     /**
 104      * The event id indicating that modification was made to the
 105      * entire hierarchy tree.
 106      */
 107     public static final int HIERARCHY_CHANGED = HIERARCHY_FIRST;
 108 
 109     /**
 110      * The event id indicating an ancestor-Container was moved.
 111      */
 112     public static final int ANCESTOR_MOVED = 1 + HIERARCHY_FIRST;
 113 
 114     /**
 115      * The event id indicating an ancestor-Container was resized.
 116      */
 117     public static final int ANCESTOR_RESIZED = 2 + HIERARCHY_FIRST;
 118 
 119     /**
 120      * Marks the last integer id for the range of ancestor event ids.
 121      */
 122     public static final int HIERARCHY_LAST = ANCESTOR_RESIZED;
 123 
 124     /**
 125      * A change flag indicates that the <code>HIERARCHY_CHANGED</code> event
 126      * was generated by a reparenting operation.
 127      */
 128     public static final int PARENT_CHANGED = 0x1;
 129 
 130     /**
 131      * A change flag indicates that the <code>HIERARCHY_CHANGED</code> event
 132      * was generated due to the changing of the hierarchy displayability.
 133      * To discern the
 134      * current displayability of the hierarchy, call the
 135      * <code>Component.isDisplayable</code> method. Displayability changes occur
 136      * in response to explicit or implicit calls of the
 137      * <code>Component.addNotify</code> and
 138      * <code>Component.removeNotify</code> methods.
 139      *
 140      * @see java.awt.Component#isDisplayable()
 141      * @see java.awt.Component#addNotify()
 142      * @see java.awt.Component#removeNotify()
 143      */
 144     public static final int DISPLAYABILITY_CHANGED = 0x2;
 145 
 146     /**
 147      * A change flag indicates that the <code>HIERARCHY_CHANGED</code> event
 148      * was generated due to the changing of the hierarchy showing state.
 149      * To discern the
 150      * current showing state of the hierarchy, call the
 151      * <code>Component.isShowing</code> method. Showing state changes occur
 152      * when either the displayability or visibility of the
 153      * hierarchy occurs. Visibility changes occur in response to explicit
 154      * or implicit calls of the <code>Component.show</code> and
 155      * <code>Component.hide</code> methods.
 156      *
 157      * @see java.awt.Component#isShowing()
 158      * @see java.awt.Component#addNotify()
 159      * @see java.awt.Component#removeNotify()
 160      * @see java.awt.Component#show()
 161      * @see java.awt.Component#hide()
 162      */
 163     public static final int SHOWING_CHANGED = 0x4;
 164 
 165     Component changed;
 166     Container changedParent;
 167     long      changeFlags;
 168 
 169     /**
 170      * Constructs an <code>HierarchyEvent</code> object to identify a
 171      * change in the <code>Component</code> hierarchy.
 172      * <p>This method throws an
 173      * <code>IllegalArgumentException</code> if <code>source</code>
 174      * is <code>null</code>.
 175      *
 176      * @param source          The <code>Component</code> object that
 177      *                        originated the event
 178      * @param id              An integer indicating the type of event.
 179      *                        For information on allowable values, see
 180      *                        the class description for {@link HierarchyEvent}
 181      * @param changed         The <code>Component</code> at the top of
 182      *                        the hierarchy which was changed
 183      * @param changedParent   The parent of the <code>changed</code> component.
 184      *                        This
 185      *                        may be the parent before or after the
 186      *                        change, depending on the type of change
 187      * @throws IllegalArgumentException if <code>source</code> is {@code null}
 188      * @see #getSource()
 189      * @see #getID()
 190      * @see #getChanged()
 191      * @see #getChangedParent()
 192      */
 193     public HierarchyEvent(Component source, int id, Component changed,
 194                           Container changedParent) {
 195         super(source, id);
 196         this.changed = changed;
 197         this.changedParent = changedParent;
 198     }
 199 
 200     /**
 201      * Constructs an <code>HierarchyEvent</code> object to identify
 202      * a change in the <code>Component</code> hierarchy.
 203      * <p> This method throws an
 204      * <code>IllegalArgumentException</code> if <code>source</code>
 205      * is <code>null</code>.
 206      *
 207      * @param source          The <code>Component</code> object that
 208      *                        originated the event
 209      * @param id              An integer indicating the type of event.
 210      *                        For information on allowable values, see
 211      *                        the class description for {@link HierarchyEvent}
 212      * @param changed         The <code>Component</code> at the top
 213      *                        of the hierarchy which was changed
 214      * @param changedParent   The parent of the <code>changed</code> component.
 215      *                        This
 216      *                        may be the parent before or after the
 217      *                        change, depending on the type of change
 218      * @param changeFlags     A bitmask which indicates the type(s) of
 219      *                        the <code>HIERARCHY_CHANGED</code> events
 220      *                        represented in this event object.
 221      *                        For information on allowable values, see
 222      *                        the class description for {@link HierarchyEvent}
 223      * @throws IllegalArgumentException if <code>source</code> is null
 224      * @see #getSource()
 225      * @see #getID()
 226      * @see #getChanged()
 227      * @see #getChangedParent()
 228      * @see #getChangeFlags()
 229      */
 230     public HierarchyEvent(Component source, int id, Component changed,
 231                           Container changedParent, long changeFlags) {
 232         super(source, id);
 233         this.changed = changed;
 234         this.changedParent = changedParent;
 235         this.changeFlags = changeFlags;
 236     }
 237 
 238     /**
 239      * Returns the originator of the event.
 240      *
 241      * @return the <code>Component</code> object that originated
 242      * the event, or <code>null</code> if the object is not a
 243      * <code>Component</code>.
 244      */
 245     public Component getComponent() {
 246         return (source instanceof Component) ? (Component)source : null;
 247     }
 248 
 249     /**
 250      * Returns the Component at the top of the hierarchy which was
 251      * changed.
 252      *
 253      * @return the changed Component
 254      */
 255     public Component getChanged() {
 256         return changed;
 257     }
 258 
 259     /**
 260      * Returns the parent of the Component returned by <code>
 261      * getChanged()</code>. For a HIERARCHY_CHANGED event where the
 262      * change was of type PARENT_CHANGED via a call to <code>
 263      * Container.add</code>, the parent returned is the parent
 264      * after the add operation. For a HIERARCHY_CHANGED event where
 265      * the change was of type PARENT_CHANGED via a call to <code>
 266      * Container.remove</code>, the parent returned is the parent
 267      * before the remove operation. For all other events and types,
 268      * the parent returned is the parent during the operation.
 269      *
 270      * @return the parent of the changed Component
 271      */
 272     public Container getChangedParent() {
 273         return changedParent;
 274     }
 275 
 276     /**
 277      * Returns a bitmask which indicates the type(s) of
 278      * HIERARCHY_CHANGED events represented in this event object.
 279      * The bits have been bitwise-ored together.
 280      *
 281      * @return the bitmask, or 0 if this is not an HIERARCHY_CHANGED
 282      * event
 283      */
 284     public long getChangeFlags() {
 285         return changeFlags;
 286     }
 287 
 288     /**
 289      * Returns a parameter string identifying this event.
 290      * This method is useful for event-logging and for debugging.
 291      *
 292      * @return a string identifying the event and its attributes
 293      */
 294     public String paramString() {
 295         String typeStr;
 296         switch(id) {
 297           case ANCESTOR_MOVED:
 298               typeStr = "ANCESTOR_MOVED ("+changed+","+changedParent+")";
 299               break;
 300           case ANCESTOR_RESIZED:
 301               typeStr = "ANCESTOR_RESIZED ("+changed+","+changedParent+")";
 302               break;
 303           case HIERARCHY_CHANGED: {
 304               typeStr = "HIERARCHY_CHANGED (";
 305               boolean first = true;
 306               if ((changeFlags & PARENT_CHANGED) != 0) {
 307                   first = false;
 308                   typeStr += "PARENT_CHANGED";
 309               }
 310               if ((changeFlags & DISPLAYABILITY_CHANGED) != 0) {
 311                   if (first) {
 312                       first = false;
 313                   } else {
 314                       typeStr += ",";
 315                   }
 316                   typeStr += "DISPLAYABILITY_CHANGED";
 317               }
 318               if ((changeFlags & SHOWING_CHANGED) != 0) {
 319                   if (first) {
 320                       first = false;
 321                   } else {
 322                       typeStr += ",";
 323                   }
 324                   typeStr += "SHOWING_CHANGED";
 325               }
 326               if (!first) {
 327                   typeStr += ",";
 328               }
 329               typeStr += changed + "," + changedParent + ")";
 330               break;
 331           }
 332           default:
 333               typeStr = "unknown type";
 334         }
 335         return typeStr;
 336     }
 337 }