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.util.EventListener;
  29 
  30 /**
  31  * The listener interface for receiving keyboard focus events on
  32  * a component.
  33  * The class that is interested in processing a focus event
  34  * either implements this interface (and all the methods it
  35  * contains) or extends the abstract <code>FocusAdapter</code> class
  36  * (overriding only the methods of interest).
  37  * The listener object created from that class is then registered with a
  38  * component using the component's <code>addFocusListener</code>
  39  * method. When the component gains or loses the keyboard focus,
  40  * the relevant method in the listener object
  41  * is invoked, and the <code>FocusEvent</code> is passed to it.
  42  *
  43  * @see FocusAdapter
  44  * @see FocusEvent
  45  * @see <a href="http://docs.oracle.com/javase/tutorial/uiswing/events/focuslistener.html">Tutorial: Writing a Focus Listener</a>
  46  *
  47  * @author Carl Quinn
  48  * @since 1.1
  49  */
  50 public interface FocusListener extends EventListener {
  51 
  52     /**
  53      * Invoked when a component gains the keyboard focus.
  54      */
  55     public void focusGained(FocusEvent e);
  56 
  57     /**
  58      * Invoked when a component loses the keyboard focus.
  59      */
  60     public void focusLost(FocusEvent e);
  61 }