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.AWTEvent;
29 import java.awt.Component;
30 import java.awt.Rectangle;
31 import javax.tools.annotation.GenerateNativeHeader;
32
33 /**
34 * A low-level event which indicates that a component moved, changed
35 * size, or changed visibility (also, the root class for the other
36 * component-level events).
37 * <P>
38 * Component events are provided for notification purposes ONLY;
39 * The AWT will automatically handle component moves and resizes
40 * internally so that GUI layout works properly regardless of
41 * whether a program is receiving these events or not.
42 * <P>
43 * In addition to serving as the base class for other component-related
44 * events (InputEvent, FocusEvent, WindowEvent, ContainerEvent),
45 * this class defines the events that indicate changes in
46 * a component's size, position, or visibility.
47 * <P>
48 * This low-level event is generated by a component object (such as a
49 * List) when the component is moved, resized, rendered invisible, or made
50 * visible again. The event is passed to every <code>ComponentListener</code>
51 * or <code>ComponentAdapter</code> object which registered to receive such
52 * events using the component's <code>addComponentListener</code> method.
53 * (<code>ComponentAdapter</code> objects implement the
54 * <code>ComponentListener</code> interface.) Each such listener object
55 * gets this <code>ComponentEvent</code> when the event occurs.
56 * <p>
57 * An unspecified behavior will be caused if the {@code id} parameter
58 * of any particular {@code ComponentEvent} instance is not
59 * in the range from {@code COMPONENT_FIRST} to {@code COMPONENT_LAST}.
60 *
61 * @see ComponentAdapter
62 * @see ComponentListener
63 * @see <a href="http://java.sun.com/docs/books/tutorial/post1.0/ui/componentlistener.html">Tutorial: Writing a Component Listener</a>
64 *
65 * @author Carl Quinn
66 * @since 1.1
67 */
68 /* No native methods here, but the constants are needed in the supporting JNI code */
69 @GenerateNativeHeader
70 public class ComponentEvent extends AWTEvent {
71
72 /**
73 * The first number in the range of ids used for component events.
74 */
75 public static final int COMPONENT_FIRST = 100;
76
77 /**
78 * The last number in the range of ids used for component events.
79 */
80 public static final int COMPONENT_LAST = 103;
81
82 /**
83 * This event indicates that the component's position changed.
84 */
85 public static final int COMPONENT_MOVED = COMPONENT_FIRST;
86
87 /**
88 * This event indicates that the component's size changed.
89 */
90 public static final int COMPONENT_RESIZED = 1 + COMPONENT_FIRST;
91
92 /**
93 * This event indicates that the component was made visible.
94 */
95 public static final int COMPONENT_SHOWN = 2 + COMPONENT_FIRST;
96
97 /**
98 * This event indicates that the component was rendered invisible.
99 */
100 public static final int COMPONENT_HIDDEN = 3 + COMPONENT_FIRST;
101
102 /*
103 * JDK 1.1 serialVersionUID
104 */
105 private static final long serialVersionUID = 8101406823902992965L;
106
107 /**
108 * Constructs a <code>ComponentEvent</code> object.
109 * <p> This method throws an
110 * <code>IllegalArgumentException</code> if <code>source</code>
111 * is <code>null</code>.
112 *
113 * @param source The <code>Component</code> that originated the event
114 * @param id An integer indicating the type of event.
115 * For information on allowable values, see
116 * the class description for {@link ComponentEvent}
117 * @throws IllegalArgumentException if <code>source</code> is null
118 * @see #getComponent()
119 * @see #getID()
120 */
121 public ComponentEvent(Component source, int id) {
122 super(source, id);
123 }
124
125 /**
126 * Returns the originator of the event.
127 *
128 * @return the <code>Component</code> object that originated
129 * the event, or <code>null</code> if the object is not a
130 * <code>Component</code>.
131 */
132 public Component getComponent() {
133 return (source instanceof Component) ? (Component)source : null;
134 }
135
136 /**
137 * Returns a parameter string identifying this event.
138 * This method is useful for event-logging and for debugging.
139 *
140 * @return a string identifying the event and its attributes
141 */
142 public String paramString() {
143 String typeStr;
144 Rectangle b = (source !=null
145 ? ((Component)source).getBounds()
146 : null);
147
148 switch(id) {
149 case COMPONENT_SHOWN:
150 typeStr = "COMPONENT_SHOWN";
151 break;
152 case COMPONENT_HIDDEN:
153 typeStr = "COMPONENT_HIDDEN";
154 break;
155 case COMPONENT_MOVED:
156 typeStr = "COMPONENT_MOVED ("+
157 b.x+","+b.y+" "+b.width+"x"+b.height+")";
158 break;
159 case COMPONENT_RESIZED:
160 typeStr = "COMPONENT_RESIZED ("+
161 b.x+","+b.y+" "+b.width+"x"+b.height+")";
162 break;
163 default:
164 typeStr = "unknown type";
165 }
166 return typeStr;
167 }
168 }