https://openjdk.java.net/ 
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package java.awt.event;

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


An event which indicates a change to the Component hierarchy to which Component belongs. 
    

  • Hierarchy Change Events (HierarchyListener)
    
      
    
    •  addition of an ancestor
    
    •  removal of an ancestor
    
    •  hierarchy made displayable
    
    •  hierarchy made undisplayable
    
    •  hierarchy shown on the screen (both visible and displayable)
    
    •  hierarchy hidden on the screen (either invisible or undisplayable)
    
    

  • Ancestor Reshape Events (HierarchyBoundsListener)
    
      
    
    •  an ancestor was resized
    
    •  an ancestor was moved
    
    




Hierarchy events are provided for notification purposes ONLY.
The AWT will automatically handle changes to the hierarchy internally so
that GUI layout and displayability works properly regardless of whether a
program is receiving these events or not.

 This event is generated by a Container object (such as a Panel) when the Container is added, removed, moved, or resized, and passed down the hierarchy. It is also generated by a Component object when that object's addNotify, removeNotify, show, or hide method is called. The ANCESTOR_MOVED and ANCESTOR_RESIZED events are dispatched to every HierarchyBoundsListener or HierarchyBoundsAdapter object which registered to receive such events using the Component's addHierarchyBoundsListener method. (HierarchyBoundsAdapter objects implement the HierarchyBoundsListener interface.) The HIERARCHY_CHANGED events are dispatched to every HierarchyListener object which registered to receive such events using the Component's addHierarchyListener method. Each such listener object gets this HierarchyEvent when the event occurs. 
 An unspecified behavior will be caused if the id parameter of any particular HierarchyEvent instance is not in the range from HIERARCHY_FIRST to HIERARCHY_LAST. 
 The changeFlags parameter of any HierarchyEvent instance takes one of the following values: 
    

  •  HierarchyEvent.PARENT_CHANGED 
  •  HierarchyEvent.DISPLAYABILITY_CHANGED 
  •  HierarchyEvent.SHOWING_CHANGED 

Assigning the value different from listed above will cause unspecified behavior.

Author:     David Mendenhall
See Also:
Since:      1.3
/**
 * An event which indicates a change to the {@code Component}
 * hierarchy to which {@code Component} belongs.
 * <ul>
 * <li>Hierarchy Change Events (HierarchyListener)
 *     <ul>
 *     <li> addition of an ancestor
 *     <li> removal of an ancestor
 *     <li> hierarchy made displayable
 *     <li> hierarchy made undisplayable
 *     <li> hierarchy shown on the screen (both visible and displayable)
 *     <li> hierarchy hidden on the screen (either invisible or undisplayable)
 *     </ul>
 * <li>Ancestor Reshape Events (HierarchyBoundsListener)
 *     <ul>
 *     <li> an ancestor was resized
 *     <li> an ancestor was moved
 *     </ul>
 * </ul>
 * <p>
 * Hierarchy events are provided for notification purposes ONLY.
 * The AWT will automatically handle changes to the hierarchy internally so
 * that GUI layout and displayability works properly regardless of whether a
 * program is receiving these events or not.
 * <p>
 * This event is generated by a Container object (such as a Panel) when the
 * Container is added, removed, moved, or resized, and passed down the
 * hierarchy. It is also generated by a Component object when that object's
 * {@code addNotify}, {@code removeNotify}, {@code show}, or
 * {@code hide} method is called. The {@code ANCESTOR_MOVED} and
 * {@code ANCESTOR_RESIZED}
 * events are dispatched to every {@code HierarchyBoundsListener} or
 * {@code HierarchyBoundsAdapter} object which registered to receive
 * such events using the Component's {@code addHierarchyBoundsListener}
 * method. ({@code HierarchyBoundsAdapter} objects implement the
 * {@code HierarchyBoundsListener} interface.) The {@code HIERARCHY_CHANGED} events are
 * dispatched to every {@code HierarchyListener} object which registered
 * to receive such events using the Component's {@code addHierarchyListener}
 * method. Each such listener object gets this {@code HierarchyEvent}
 * when the event occurs.
 * <p>
 * An unspecified behavior will be caused if the {@code id} parameter
 * of any particular {@code HierarchyEvent} instance is not
 * in the range from {@code HIERARCHY_FIRST} to {@code HIERARCHY_LAST}.
 * <br>
 * The {@code changeFlags} parameter of any {@code HierarchyEvent} instance takes one of the following
 * values:
 * <ul>
 * <li> {@code HierarchyEvent.PARENT_CHANGED}
 * <li> {@code HierarchyEvent.DISPLAYABILITY_CHANGED}
 * <li> {@code HierarchyEvent.SHOWING_CHANGED}
 * </ul>
 * Assigning the value different from listed above will cause unspecified behavior.
 *
 * @author      David Mendenhall
 * @see         HierarchyListener
 * @see         HierarchyBoundsAdapter
 * @see         HierarchyBoundsListener
 * @since       1.3
 */
public class HierarchyEvent extends AWTEvent {
    /*
     * serialVersionUID
     */
    private static final long serialVersionUID = -5337576970038043990L;

    
Marks the first integer id for the range of hierarchy event ids.

/**
     * Marks the first integer id for the range of hierarchy event ids.
     */
    public static final int HIERARCHY_FIRST = 1400; // 1300 used by sun.awt.windows.ModalityEvent

    
The event id indicating that modification was made to the
entire hierarchy tree.

/**
     * The event id indicating that modification was made to the
     * entire hierarchy tree.
     */
    public static final int HIERARCHY_CHANGED = HIERARCHY_FIRST;

    
The event id indicating an ancestor-Container was moved.

/**
     * The event id indicating an ancestor-Container was moved.
     */
    public static final int ANCESTOR_MOVED = 1 + HIERARCHY_FIRST;

    
The event id indicating an ancestor-Container was resized.

/**
     * The event id indicating an ancestor-Container was resized.
     */
    public static final int ANCESTOR_RESIZED = 2 + HIERARCHY_FIRST;

    
Marks the last integer id for the range of ancestor event ids.

/**
     * Marks the last integer id for the range of ancestor event ids.
     */
    public static final int HIERARCHY_LAST = ANCESTOR_RESIZED;

    
A change flag indicates that the HIERARCHY_CHANGED event was generated by a reparenting operation. 
/**
     * A change flag indicates that the {@code HIERARCHY_CHANGED} event
     * was generated by a reparenting operation.
     */
    public static final int PARENT_CHANGED = 0x1;

    
A change flag indicates that the HIERARCHY_CHANGED event was generated due to the changing of the hierarchy displayability. To discern the current displayability of the hierarchy, call the Component.isDisplayable method. Displayability changes occur in response to explicit or implicit calls of the Component.addNotify and Component.removeNotify methods. 
See Also:
/**
     * A change flag indicates that the {@code HIERARCHY_CHANGED} event
     * was generated due to the changing of the hierarchy displayability.
     * To discern the
     * current displayability of the hierarchy, call the
     * {@code Component.isDisplayable} method. Displayability changes occur
     * in response to explicit or implicit calls of the
     * {@code Component.addNotify} and
     * {@code Component.removeNotify} methods.
     *
     * @see java.awt.Component#isDisplayable()
     * @see java.awt.Component#addNotify()
     * @see java.awt.Component#removeNotify()
     */
    public static final int DISPLAYABILITY_CHANGED = 0x2;

    
A change flag indicates that the HIERARCHY_CHANGED event was generated due to the changing of the hierarchy showing state. To discern the current showing state of the hierarchy, call the Component.isShowing method. Showing state changes occur when either the displayability or visibility of the hierarchy occurs. Visibility changes occur in response to explicit or implicit calls of the Component.show and Component.hide methods. 
See Also:
/**
     * A change flag indicates that the {@code HIERARCHY_CHANGED} event
     * was generated due to the changing of the hierarchy showing state.
     * To discern the
     * current showing state of the hierarchy, call the
     * {@code Component.isShowing} method. Showing state changes occur
     * when either the displayability or visibility of the
     * hierarchy occurs. Visibility changes occur in response to explicit
     * or implicit calls of the {@code Component.show} and
     * {@code Component.hide} methods.
     *
     * @see java.awt.Component#isShowing()
     * @see java.awt.Component#addNotify()
     * @see java.awt.Component#removeNotify()
     * @see java.awt.Component#show()
     * @see java.awt.Component#hide()
     */
    public static final int SHOWING_CHANGED = 0x4;

    Component changed;
    Container changedParent;
    long      changeFlags;

    
Constructs an HierarchyEvent object to identify a change in the Component hierarchy. 
This method throws an IllegalArgumentException if source is null. 
Params:
  • source –  The Component object that originated the event
  • id –  An integer indicating the type of event. For information on allowable values, see the class description for HierarchyEvent
  • changed –  The Component at the top of the hierarchy which was changed
  • changedParent –  The parent of the changed component. This may be the parent before or after the change, depending on the type of change
Throws:
See Also:
/**
     * Constructs an {@code HierarchyEvent} object to identify a
     * change in the {@code Component} hierarchy.
     * <p>This method throws an
     * {@code IllegalArgumentException} if {@code source}
     * is {@code null}.
     *
     * @param source          The {@code Component} object that
     *                        originated the event
     * @param id              An integer indicating the type of event.
     *                        For information on allowable values, see
     *                        the class description for {@link HierarchyEvent}
     * @param changed         The {@code Component} at the top of
     *                        the hierarchy which was changed
     * @param changedParent   The parent of the {@code changed} component.
     *                        This
     *                        may be the parent before or after the
     *                        change, depending on the type of change
     * @throws IllegalArgumentException if {@code source} is {@code null}
     * @see #getSource()
     * @see #getID()
     * @see #getChanged()
     * @see #getChangedParent()
     */
    public HierarchyEvent(Component source, int id, Component changed,
                          Container changedParent) {
        super(source, id);
        this.changed = changed;
        this.changedParent = changedParent;
    }

    
Constructs an HierarchyEvent object to identify a change in the Component hierarchy. 
 This method throws an IllegalArgumentException if source is null. 
Params:
  • source –  The Component object that originated the event
  • id –  An integer indicating the type of event. For information on allowable values, see the class description for HierarchyEvent
  • changed –  The Component at the top of the hierarchy which was changed
  • changedParent –  The parent of the changed component. This may be the parent before or after the change, depending on the type of change
  • changeFlags –  A bitmask which indicates the type(s) of the HIERARCHY_CHANGED events represented in this event object. For information on allowable values, see the class description for HierarchyEvent
Throws:
See Also:
/**
     * Constructs an {@code HierarchyEvent} object to identify
     * a change in the {@code Component} hierarchy.
     * <p> This method throws an
     * {@code IllegalArgumentException} if {@code source}
     * is {@code null}.
     *
     * @param source          The {@code Component} object that
     *                        originated the event
     * @param id              An integer indicating the type of event.
     *                        For information on allowable values, see
     *                        the class description for {@link HierarchyEvent}
     * @param changed         The {@code Component} at the top
     *                        of the hierarchy which was changed
     * @param changedParent   The parent of the {@code changed} component.
     *                        This
     *                        may be the parent before or after the
     *                        change, depending on the type of change
     * @param changeFlags     A bitmask which indicates the type(s) of
     *                        the {@code HIERARCHY_CHANGED} events
     *                        represented in this event object.
     *                        For information on allowable values, see
     *                        the class description for {@link HierarchyEvent}
     * @throws IllegalArgumentException if {@code source} is null
     * @see #getSource()
     * @see #getID()
     * @see #getChanged()
     * @see #getChangedParent()
     * @see #getChangeFlags()
     */
    public HierarchyEvent(Component source, int id, Component changed,
                          Container changedParent, long changeFlags) {
        super(source, id);
        this.changed = changed;
        this.changedParent = changedParent;
        this.changeFlags = changeFlags;
    }

    
Returns the originator of the event.

Returns:the Component object that originated the event, or null if the object is not a Component.
/**
     * Returns the originator of the event.
     *
     * @return the {@code Component} object that originated
     * the event, or {@code null} if the object is not a
     * {@code Component}.
     */
    public Component getComponent() {
        return (source instanceof Component) ? (Component)source : null;
    }

    
Returns the Component at the top of the hierarchy which was
changed.

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

    
Returns the parent of the Component returned by getChanged(). For a HIERARCHY_CHANGED event where the change was of type PARENT_CHANGED via a call to Container.add, the parent returned is the parent after the add operation. For a HIERARCHY_CHANGED event where the change was of type PARENT_CHANGED via a call to Container.remove, the parent returned is the parent before the remove operation. For all other events and types, the parent returned is the parent during the operation. 
Returns:the parent of the changed Component
/**
     * Returns the parent of the Component returned by
     * {@code getChanged()}. For a HIERARCHY_CHANGED event where the
     * change was of type PARENT_CHANGED via a call to
     * {@code Container.add}, the parent returned is the parent
     * after the add operation. For a HIERARCHY_CHANGED event where
     * the change was of type PARENT_CHANGED via a call to
     * {@code Container.remove}, the parent returned is the parent
     * before the remove operation. For all other events and types,
     * the parent returned is the parent during the operation.
     *
     * @return the parent of the changed Component
     */
    public Container getChangedParent() {
        return changedParent;
    }

    
Returns a bitmask which indicates the type(s) of
HIERARCHY_CHANGED events represented in this event object.
The bits have been bitwise-ored together.

Returns:the bitmask, or 0 if this is not an HIERARCHY_CHANGED
event
/**
     * Returns a bitmask which indicates the type(s) of
     * HIERARCHY_CHANGED events represented in this event object.
     * The bits have been bitwise-ored together.
     *
     * @return the bitmask, or 0 if this is not an HIERARCHY_CHANGED
     * event
     */
    public long getChangeFlags() {
        return changeFlags;
    }

    
Returns a parameter string identifying this event.
This method is useful for event-logging and for debugging.

Returns:a string identifying the event and its attributes
/**
     * Returns a parameter string identifying this event.
     * This method is useful for event-logging and for debugging.
     *
     * @return a string identifying the event and its attributes
     */
    public String paramString() {
        String typeStr;
        switch(id) {
          case ANCESTOR_MOVED:
              typeStr = "ANCESTOR_MOVED ("+changed+","+changedParent+")";
              break;
          case ANCESTOR_RESIZED:
              typeStr = "ANCESTOR_RESIZED ("+changed+","+changedParent+")";
              break;
          case HIERARCHY_CHANGED: {
              typeStr = "HIERARCHY_CHANGED (";
              boolean first = true;
              if ((changeFlags & PARENT_CHANGED) != 0) {
                  first = false;
                  typeStr += "PARENT_CHANGED";
              }
              if ((changeFlags & DISPLAYABILITY_CHANGED) != 0) {
                  if (first) {
                      first = false;
                  } else {
                      typeStr += ",";
                  }
                  typeStr += "DISPLAYABILITY_CHANGED";
              }
              if ((changeFlags & SHOWING_CHANGED) != 0) {
                  if (first) {
                      first = false;
                  } else {
                      typeStr += ",";
                  }
                  typeStr += "SHOWING_CHANGED";
              }
              if (!first) {
                  typeStr += ",";
              }
              typeStr += changed + "," + changedParent + ")";
              break;
          }
          default:
              typeStr = "unknown type";
        }
        return typeStr;
    }
}