1 /*

     2  * Copyright 2000-2001 Sun Microsystems, Inc.  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.  Sun designates this

     8  * particular file as subject to the "Classpath" exception as provided

     9  * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

    22  * CA 95054 USA or visit www.sun.com if you need additional information or

    23  * have any questions.

    24  */

    25 package java.awt;

    26 

    27 import java.awt.event.KeyEvent;

    28 

    29 

    30 /**

    31  * A KeyEventDispatcher cooperates with the current KeyboardFocusManager in the

    32  * targeting and dispatching of all KeyEvents. KeyEventDispatchers registered

    33  * with the current KeyboardFocusManager will receive KeyEvents before they are

    34  * dispatched to their targets, allowing each KeyEventDispatcher to retarget

    35  * the event, consume it, dispatch the event itself, or make other changes.

    36  * <p>

    37  * Note that KeyboardFocusManager itself implements KeyEventDispatcher. By

    38  * default, the current KeyboardFocusManager will be the sink for all KeyEvents

    39  * not dispatched by the registered KeyEventDispatchers. The current

    40  * KeyboardFocusManager cannot be completely deregistered as a

    41  * KeyEventDispatcher. However, if a KeyEventDispatcher reports that it

    42  * dispatched the KeyEvent, regardless of whether it actually did so, the

    43  * KeyboardFocusManager will take no further action with regard to the

    44  * KeyEvent. (While it is possible for client code to register the current

    45  * KeyboardFocusManager as a KeyEventDispatcher one or more times, this is

    46  * usually unnecessary and not recommended.)

    47  *

    48  * @author David Mendenhall

    49  *

    50  * @see KeyboardFocusManager#addKeyEventDispatcher

    51  * @see KeyboardFocusManager#removeKeyEventDispatcher

    52  * @since 1.4

    53  */

    54 public interface KeyEventDispatcher {

    55 

    56     /**

    57      * This method is called by the current KeyboardFocusManager requesting

    58      * that this KeyEventDispatcher dispatch the specified event on its behalf.

    59      * This KeyEventDispatcher is free to retarget the event, consume it,

    60      * dispatch it itself, or make other changes. This capability is typically

    61      * used to deliver KeyEvents to Components other than the focus owner. This

    62      * can be useful when navigating children of non-focusable Windows in an

    63      * accessible environment, for example. Note that if a KeyEventDispatcher

    64      * dispatches the KeyEvent itself, it must use <code>redispatchEvent</code>

    65      * to prevent the current KeyboardFocusManager from recursively requesting

    66      * that this KeyEventDispatcher dispatch the event again.

    67      * <p>

    68      * If an implementation of this method returns <code>false</code>, then

    69      * the KeyEvent is passed to the next KeyEventDispatcher in the chain,

    70      * ending with the current KeyboardFocusManager. If an implementation

    71      * returns <code>true</code>, the KeyEvent is assumed to have been

    72      * dispatched (although this need not be the case), and the current

    73      * KeyboardFocusManager will take no further action with regard to the

    74      * KeyEvent. In such a case,

    75      * <code>KeyboardFocusManager.dispatchEvent</code> should return

    76      * <code>true</code> as well. If an implementation consumes the KeyEvent,

    77      * but returns <code>false</code>, the consumed event will still be passed

    78      * to the next KeyEventDispatcher in the chain. It is important for

    79      * developers to check whether the KeyEvent has been consumed before

    80      * dispatching it to a target. By default, the current KeyboardFocusManager

    81      * will not dispatch a consumed KeyEvent.

    82      *

    83      * @param e the KeyEvent to dispatch

    84      * @return <code>true</code> if the KeyboardFocusManager should take no

    85      *         further action with regard to the KeyEvent; <code>false</code>

    86      *         otherwise

    87      * @see KeyboardFocusManager#redispatchEvent

    88      */

    89     boolean dispatchKeyEvent(KeyEvent e);

    90 }