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 /**
29 * An abstract adapter class for receiving keyboard focus events.
30 * The methods in this class are empty. This class exists as
31 * convenience for creating listener objects.
32 * <P>
33 * Extend this class to create a {@code FocusEvent} listener
34 * and override the methods for the events of interest. (If you implement the
35 * {@code FocusListener} interface, you have to define all of
36 * the methods in it. This abstract class defines null methods for them
37 * all, so you can only have to define methods for events you care about.)
38 * <P>
39 * Create a listener object using the extended class and then register it with
40 * a component using the component's {@code addFocusListener}
41 * method. When the component gains or loses the keyboard focus,
42 * the relevant method in the listener object is invoked,
43 * and the {@code FocusEvent} is passed to it.
44 *
45 * @see FocusEvent
46 * @see FocusListener
47 * @see <a href="https://docs.oracle.com/javase/tutorial/uiswing/events/focuslistener.html">Tutorial: Writing a Focus Listener</a>
48 *
49 * @author Carl Quinn
50 * @since 1.1
51 */
52 public abstract class FocusAdapter implements FocusListener {
53 /**
54 * Invoked when a component gains the keyboard focus.
55 */
56 public void focusGained(FocusEvent e) {}
57
58 /**
59 * Invoked when a component loses the keyboard focus.
60 */
61 public void focusLost(FocusEvent e) {}
62 }
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