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
26 package java.awt.event;
27
28 import java.awt.AWTEvent;
29 import java.awt.Component;
30 import java.awt.Rectangle;
31 import java.lang.annotation.Native;
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="https://docs.oracle.com/javase/tutorial/uiswing/events/componentlistener.html">Tutorial: Writing a Component Listener</a>
64 *
65 * @author Carl Quinn
66 * @since 1.1
67 */
68 public class ComponentEvent extends AWTEvent {
69
70 /**
71 * The first number in the range of ids used for component events.
72 */
73 public static final int COMPONENT_FIRST = 100;
74
75 /**
76 * The last number in the range of ids used for component events.
77 */
78 public static final int COMPONENT_LAST = 103;
79
80 /**
81 * This event indicates that the component's position changed.
82 */
83 @Native public static final int COMPONENT_MOVED = COMPONENT_FIRST;
84
85 /**
86 * This event indicates that the component's size changed.
87 */
88 @Native public static final int COMPONENT_RESIZED = 1 + COMPONENT_FIRST;
89
90 /**
91 * This event indicates that the component was made visible.
92 */
93 @Native public static final int COMPONENT_SHOWN = 2 + COMPONENT_FIRST;
94
95 /**
96 * This event indicates that the component was rendered invisible.
97 */
98 @Native public static final int COMPONENT_HIDDEN = 3 + COMPONENT_FIRST;
99
100 /*
101 * JDK 1.1 serialVersionUID
102 */
103 private static final long serialVersionUID = 8101406823902992965L;
104
105 /**
106 * Constructs a <code>ComponentEvent</code> object.
107 * <p> This method throws an
108 * <code>IllegalArgumentException</code> if <code>source</code>
109 * is <code>null</code>.
110 *
111 * @param source The <code>Component</code> that originated the event
112 * @param id An integer indicating the type of event.
113 * For information on allowable values, see
114 * the class description for {@link ComponentEvent}
115 * @throws IllegalArgumentException if <code>source</code> is null
116 * @see #getComponent()
117 * @see #getID()
118 */
119 public ComponentEvent(Component source, int id) {
120 super(source, id);
121 }
122
123 /**
124 * Returns the originator of the event.
125 *
126 * @return the <code>Component</code> object that originated
127 * the event, or <code>null</code> if the object is not a
128 * <code>Component</code>.
129 */
130 public Component getComponent() {
131 return (source instanceof Component) ? (Component)source : null;
132 }
133
134 /**
135 * Returns a parameter string identifying this event.
136 * This method is useful for event-logging and for debugging.
137 *
138 * @return a string identifying the event and its attributes
139 */
140 public String paramString() {
141 String typeStr;
142 Rectangle b = (source !=null
143 ? ((Component)source).getBounds()
144 : null);
145
146 switch(id) {
147 case COMPONENT_SHOWN:
148 typeStr = "COMPONENT_SHOWN";
149 break;
150 case COMPONENT_HIDDEN:
151 typeStr = "COMPONENT_HIDDEN";
152 break;
153 case COMPONENT_MOVED:
154 typeStr = "COMPONENT_MOVED ("+
155 b.x+","+b.y+" "+b.width+"x"+b.height+")";
156 break;
157 case COMPONENT_RESIZED:
158 typeStr = "COMPONENT_RESIZED ("+
159 b.x+","+b.y+" "+b.width+"x"+b.height+")";
160 break;
161 default:
162 typeStr = "unknown type";
163 }
164 return typeStr;
165 }
166 }