1/*
2 * Copyright (c) 1996, 2013, 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
26package java.awt.event;
27
28import java.awt.Container;
29import java.awt.Component;
30
31/**
32 * A low-level event which indicates that a container's contents
33 * changed because a component was added or removed.
34 * <P>
35 * Container events are provided for notification purposes ONLY;
36 * The AWT will automatically handle changes to the containers
37 * contents internally so that the program works properly regardless of
38 * whether the program is receiving these events or not.
39 * <P>
40 * This low-level event is generated by a container object (such as a
41 * Panel) when a component is added to it or removed from it.
42 * The event is passed to every {@code ContainerListener}
43 * or {@code ContainerAdapter} object which registered to receive such
44 * events using the component's {@code addContainerListener} method.
45 * ({@code ContainerAdapter} objects implement the
46 * {@code ContainerListener} interface.) Each such listener object
47 * gets this {@code ContainerEvent} when the event occurs.
48 * <p>
49 * An unspecified behavior will be caused if the {@code id} parameter
50 * of any particular {@code ContainerEvent} instance is not
51 * in the range from {@code CONTAINER_FIRST} to {@code CONTAINER_LAST}.
52 *
53 * @see ContainerAdapter
54 * @see ContainerListener
55 * @see <a href="http://docs.oracle.com/javase/tutorial/uiswing/events/containerlistener.html">Tutorial: Writing a Container Listener</a>
56 *
57 * @author Tim Prinzing
58 * @author Amy Fowler
59 * @since 1.1
60 */
61public class ContainerEvent extends ComponentEvent {
62
63    /**
64     * The first number in the range of ids used for container events.
65     */
66    public static final int CONTAINER_FIRST             = 300;
67
68    /**
69     * The last number in the range of ids used for container events.
70     */
71    public static final int CONTAINER_LAST              = 301;
72
73   /**
74     * This event indicates that a component was added to the container.
75     */
76    public static final int COMPONENT_ADDED     = CONTAINER_FIRST;
77
78    /**
79     * This event indicates that a component was removed from the container.
80     */
81    public static final int COMPONENT_REMOVED = 1 + CONTAINER_FIRST;
82
83    /**
84     * The non-null component that is being added or
85     * removed from the Container.
86     *
87     * @serial
88     * @see #getChild()
89     */
90    Component child;
91
92    /*
93     * JDK 1.1 serialVersionUID
94     */
95    private static final long serialVersionUID = -4114942250539772041L;
96
97    /**
98     * Constructs a {@code ContainerEvent} object.
99     * <p> This method throws an
100     * {@code IllegalArgumentException} if {@code source}
101     * is {@code null}.
102     *
103     * @param source The {@code Component} object (container)
104     *               that originated the event
105     * @param id     An integer indicating the type of event.
106     *                     For information on allowable values, see
107     *                     the class description for {@link ContainerEvent}
108     * @param child  the component that was added or removed
109     * @throws IllegalArgumentException if {@code source} is null
110     * @see #getContainer()
111     * @see #getID()
112     * @see #getChild()
113     */
114    public ContainerEvent(Component source, int id, Component child) {
115        super(source, id);
116        this.child = child;
117    }
118
119    /**
120     * Returns the originator of the event.
121     *
122     * @return the {@code Container} object that originated
123     * the event, or {@code null} if the object is not a
124     * {@code Container}.
125     */
126    public Container getContainer() {
127        return (source instanceof Container) ? (Container)source : null;
128    }
129
130    /**
131     * Returns the component that was affected by the event.
132     *
133     * @return the Component object that was added or removed
134     */
135    public Component getChild() {
136        return child;
137    }
138
139    /**
140     * Returns a parameter string identifying this event.
141     * This method is useful for event-logging and for debugging.
142     *
143     * @return a string identifying the event and its attributes
144     */
145    public String paramString() {
146        String typeStr;
147        switch(id) {
148          case COMPONENT_ADDED:
149              typeStr = "COMPONENT_ADDED";
150              break;
151          case COMPONENT_REMOVED:
152              typeStr = "COMPONENT_REMOVED";
153              break;
154          default:
155              typeStr = "unknown type";
156        }
157        return typeStr + ",child="+child.getName();
158    }
159}
160