HierarchyEvent.java

/* HierarchyEvent.java -- generated for a change in hierarchy
   Copyright (C) 2000, 2002 Free Software Foundation

This file is part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
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02111-1307 USA.

Linking this library statically or dynamically with other modules is
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As a special exception, the copyright holders of this library give you
permission to link this library with independent modules to produce an
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package java.awt.event;

import java.awt.AWTEvent;
import java.awt.Component;
import java.awt.Container;

/**
 * This class represents an event generated for an ancestor component which
 * may affect this component. These events normally do not need to be handled
 * by the application, since the AWT system automatically takes care of them.
 *
 * <p>There are two types of hierarchy events. The first type is handled by
 * HierarchyListener, and includes addition or removal of an ancestor, or
 * an ancestor changing its on-screen status (visible and/or displayble). The
 * second type is handled by HierarchyBoundsListener, and includes resizing
 * or moving of an ancestor.
 *
 * @author Bryce McKinlay
 * @see HierarchyListener
 * @see HierarchyBoundsAdapter
 * @see HierarchyBoundsListener
 * @since 1.3
 * @status updated to 1.4
 */
public class HierarchyEvent extends AWTEvent
{
  /**
   * Compatible with JDK 1.3+.
   */
  private static final long serialVersionUID = -5337576970038043990L;

  /** This is the first id in the range of ids used by this class. */
  public static final int HIERARCHY_FIRST = 1400;

  /** This id indicates that the hierarchy tree changed. */
  public static final int HIERARCHY_CHANGED = 1400;

  /** This id indicates that an ancestor was moved. */
  public static final int ANCESTOR_MOVED = 1401;

  /** This id indicates that an ancestor was resized. */
  public static final int ANCESTOR_RESIZED = 1402;

  /** This is the last id in the range of ids used by this class. */
  public static final int HIERARCHY_LAST = 1402;

  /** This indicates that the HIERARCHY_CHANGED is a changed parent. */
  public static final int PARENT_CHANGED = 1;

  /**
   * This indicates that the HIERARCHY_CHANGED is caused by a change in
   * displayability.
   *
   * @see Component#isDisplayable()
   * @see Component#addNotify()
   * @see Component#removeNotify()
   */
  public static final int DISPLAYABILITY_CHANGED = 2;

  /**
   * This indicates that the HIERARCHY_CHANGED is a changed visibility.
   *
   * @see Component#isShowing()
   * @see Component#addNotify()
   * @see Component#removeNotify()
   * @see Component#show()
   * @see Component#hide()
   */
  public static final int SHOWING_CHANGED = 4;

  /**
   * The component at the top of the changed hierarchy.
   *
   * @serial the top component changed
   */
  private final Component changed;

  /**
   * The parent of this component, either before or after the change depending
   * on the type of change.
   *
   * @serial the parent component changed
   */
  private final Container changedParent;

  /**
   * The bitmask of HIERARCHY_CHANGED event types.
   *
   * @serial the change flags
   */
  private final long changeFlags;

  /**
   * Initializes a new instance of <code>HierarchyEvent</code> with the
   * specified parameters. Note that an invalid id leads to unspecified
   * results.
   *
   * @param source the component whose hierarchy changed
   * @param id the event id
   * @param changed the top component in the tree of changed hierarchy
   * @param changedParent the updated parent of this object
   * @throws IllegalArgumentException if source is null
   */
  public HierarchyEvent(Component source, int id, Component changed,
                        Container changedParent)
  {
    this(source, id, changed, changedParent, 0);
  }

  /**
   * Initializes a new instance of <code>HierarchyEvent</code> with the
   * specified parameters. Note that an invalid id leads to unspecified
   * results.
   *
   * @param source the component whose hierarchy changed
   * @param id the event id
   * @param changed the top component in the tree of changed hierarchy
   * @param changedParent the updated parent of this object
   * @param changeFlags the bitmask of specific HIERARCHY_CHANGED events
   * @throws IllegalArgumentException if source is null
   */
  public HierarchyEvent(Component source, int id, Component changed,
                        Container changedParent, long changeFlags)
  {
    super(source, id);
    this.changed = changed;
    this.changedParent = changedParent;
    this.changeFlags = changeFlags;
  }

  /**
   * This method returns the event source as a <code>Component</code>. If the
   * source has subsequently been modified to a non-Component, this returns
   * null.
   *
   * @return the event source as a <code>Component</code>, or null
   */
  public Component getComponent()
  {
    return source instanceof Component ? (Component) source : null;
  }

  /**
   * Returns the component at the top of the hierarchy which changed.
   *
   * @return the top changed component
   */
  public Component getChanged()
  {
    return changed;
  }

  /**
   * Returns the parent of the component listed in <code>getChanged()</code>.
   * If the cause of this event was <code>Container.add</code>, this is the
   * new parent; if the cause was <code>Container.remove</code>, this is the
   * old parent; otherwise it is the unchanged parent.
   *
   * @return the parent container of the changed component
   */
  public Container getChangedParent()
  {
    return changedParent;
  }

  /**
   * If this is a HIERARCHY_CHANGED event, this returns a bitmask of the
   * types of changes that took place.
   *
   * @return the bitwise or of hierarchy change types, or 0
   * @see #PARENT_CHANGED
   * @see #DISPLAYABILITY_CHANGED
   * @see #SHOWING_CHANGED
   */
  public long getChangeFlags()
  {
    return changeFlags;
  }

  /**
   * This method returns a string identifying this event. This is the field
   * name of the id type, followed by a parenthesized listing of the changed
   * component and its parent container. In addition, if the type is
   * HIERARCHY_CHANGED, the flags preceed the changed component, in the
   * order PARENT_CHANGED, DISPLAYABILITY_CHANGED, and SHOWING_CHANGED.
   *
   * @return a string identifying this event
   */
  public String paramString()
  {
    StringBuffer r = new StringBuffer();
    switch (id)
      {
      case HIERARCHY_CHANGED:
        r.append("HIERARCHY_CHANGED (");
        if ((changeFlags & PARENT_CHANGED) != 0)
          r.append("PARENT_CHANGED,");
        if ((changeFlags & DISPLAYABILITY_CHANGED) != 0)
          r.append("DISPLAYABILITY_CHANGED,");
        if ((changeFlags & SHOWING_CHANGED) != 0)
          r.append("SHOWING_CHANGED,");
        break;
      case ANCESTOR_MOVED:
        r.append("ANCESTOR_MOVED (");
        break;
      case ANCESTOR_RESIZED:
        r.append("ANCESTOR_RESIZED (");
        break;
      default:
        return "unknown type";
      }
    r.append(changed).append(',').append(changedParent).append(')');
    return r.toString();
  }
} // class HierarchyEvent