Java example source code file (KeyEventPostProcessor.java)

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Java - Java tags/keywords

awt, event, functionalinterface, keyeventpostprocessor

The KeyEventPostProcessor.java Java example source code

/*
 * Copyright (c) 2001, 2013, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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 */
package java.awt;

import java.awt.event.KeyEvent;


/**
 * A KeyEventPostProcessor cooperates with the current KeyboardFocusManager
 * in the final resolution of all unconsumed KeyEvents. KeyEventPostProcessors
 * registered with the current KeyboardFocusManager will receive KeyEvents
 * after the KeyEvents have been dispatched to and handled by their targets.
 * KeyEvents that would have been otherwise discarded because no Component in
 * the application currently owns the focus will also be forwarded to
 * registered KeyEventPostProcessors. This will allow applications to implement
 * features that require global KeyEvent post-handling, such as menu shortcuts.
 * <p>
 * Note that the KeyboardFocusManager itself implements KeyEventPostProcessor.
 * By default, the current KeyboardFocusManager will be the final
 * KeyEventPostProcessor in the chain. The current KeyboardFocusManager cannot
 * be completely deregistered as a KeyEventPostProcessor. However, if a
 * KeyEventPostProcessor reports that no further post-processing of the
 * KeyEvent should take place, the AWT will consider the event fully handled
 * and will take no additional action with regard to the event. (While it is
 * possible for client code to register the current KeyboardFocusManager as
 * a KeyEventPostProcessor one or more times, this is usually unnecessary and
 * not recommended.)
 *
 * @author David Mendenhall
 *
 * @see KeyboardFocusManager#addKeyEventPostProcessor
 * @see KeyboardFocusManager#removeKeyEventPostProcessor
 * @since 1.4
 */
@FunctionalInterface
public interface KeyEventPostProcessor {

    /**
     * This method is called by the current KeyboardFocusManager, requesting
     * that this KeyEventPostProcessor perform any necessary post-processing
     * which should be part of the KeyEvent's final resolution. At the time
     * this method is invoked, typically the KeyEvent has already been
     * dispatched to and handled by its target. However, if no Component in
     * the application currently owns the focus, then the KeyEvent has not
     * been dispatched to any Component. Typically, KeyEvent post-processing
     * will be used to implement features which require global KeyEvent
     * post-handling, such as menu shortcuts. Note that if a
     * KeyEventPostProcessor wishes to dispatch the KeyEvent, it must use
     * <code>redispatchEvent to prevent the AWT from recursively
     * requesting that this KeyEventPostProcessor perform post-processing
     * of the event again.
     * <p>
     * If an implementation of this method returns <code>false, then the
     * KeyEvent is passed to the next KeyEventPostProcessor in the chain,
     * ending with the current KeyboardFocusManager. If an implementation
     * returns <code>true, the KeyEvent is assumed to have been fully
     * handled (although this need not be the case), and the AWT will take no
     * further action with regard to the KeyEvent. If an implementation
     * consumes the KeyEvent but returns <code>false, the consumed
     * event will still be passed to the next KeyEventPostProcessor in the
     * chain. It is important for developers to check whether the KeyEvent has
     * been consumed before performing any post-processing of the KeyEvent. By
     * default, the current KeyboardFocusManager will perform no post-
     * processing in response to a consumed KeyEvent.
     *
     * @param e the KeyEvent to post-process
     * @return <code>true if the AWT should take no further action with
     *         regard to the KeyEvent; <code>false otherwise
     * @see KeyboardFocusManager#redispatchEvent
     */
    boolean postProcessKeyEvent(KeyEvent e);
}