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    1   /*
    2    * Copyright (c) 2000, 2001, 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   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   }

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