1 /*
2 * Copyright (c) 1996, 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.Container;
29 import 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</code>
43 * or <code>ContainerAdapter</code> object which registered to receive such
44 * events using the component's <code>addContainerListener</code> method.
45 * (<code>ContainerAdapter</code> objects implement the
46 * <code>ContainerListener</code> interface.) Each such listener object
47 * gets this <code>ContainerEvent</code> 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 */
61 public 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</code> object.
99 * <p> This method throws an
100 * <code>IllegalArgumentException</code> if <code>source</code>
101 * is <code>null</code>.
102 *
103 * @param source The <code>Component</code> 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</code> 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</code> object that originated
123 * the event, or <code>null</code> if the object is not a
124 * <code>Container</code>.
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 }