Java tutorial
/* * Copyright (c) 2000, 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 * or visit www.oracle.com if you need additional information or have any * questions. */ package java.awt; import java.awt.event.KeyEvent; /** * A KeyEventDispatcher cooperates with the current KeyboardFocusManager in the * targeting and dispatching of all KeyEvents. KeyEventDispatchers registered * with the current KeyboardFocusManager will receive KeyEvents before they are * dispatched to their targets, allowing each KeyEventDispatcher to retarget * the event, consume it, dispatch the event itself, or make other changes. * <p> * Note that KeyboardFocusManager itself implements KeyEventDispatcher. By * default, the current KeyboardFocusManager will be the sink for all KeyEvents * not dispatched by the registered KeyEventDispatchers. The current * KeyboardFocusManager cannot be completely deregistered as a * KeyEventDispatcher. However, if a KeyEventDispatcher reports that it * dispatched the KeyEvent, regardless of whether it actually did so, the * KeyboardFocusManager will take no further action with regard to the * KeyEvent. (While it is possible for client code to register the current * KeyboardFocusManager as a KeyEventDispatcher one or more times, this is * usually unnecessary and not recommended.) * * @author David Mendenhall * * @see KeyboardFocusManager#addKeyEventDispatcher * @see KeyboardFocusManager#removeKeyEventDispatcher * @since 1.4 */ @FunctionalInterface public interface KeyEventDispatcher { /** * This method is called by the current KeyboardFocusManager requesting * that this KeyEventDispatcher dispatch the specified event on its behalf. * This KeyEventDispatcher is free to retarget the event, consume it, * dispatch it itself, or make other changes. This capability is typically * used to deliver KeyEvents to Components other than the focus owner. This * can be useful when navigating children of non-focusable Windows in an * accessible environment, for example. Note that if a KeyEventDispatcher * dispatches the KeyEvent itself, it must use {@code redispatchEvent} * to prevent the current KeyboardFocusManager from recursively requesting * that this KeyEventDispatcher dispatch the event again. * <p> * If an implementation of this method returns {@code false}, then * the KeyEvent is passed to the next KeyEventDispatcher in the chain, * ending with the current KeyboardFocusManager. If an implementation * returns {@code true}, the KeyEvent is assumed to have been * dispatched (although this need not be the case), and the current * KeyboardFocusManager will take no further action with regard to the * KeyEvent. In such a case, * {@code KeyboardFocusManager.dispatchEvent} should return * {@code true} as well. If an implementation consumes the KeyEvent, * but returns {@code false}, the consumed event will still be passed * to the next KeyEventDispatcher in the chain. It is important for * developers to check whether the KeyEvent has been consumed before * dispatching it to a target. By default, the current KeyboardFocusManager * will not dispatch a consumed KeyEvent. * * @param e the KeyEvent to dispatch * @return {@code true} if the KeyboardFocusManager should take no * further action with regard to the KeyEvent; {@code false} * otherwise * @see KeyboardFocusManager#redispatchEvent */ boolean dispatchKeyEvent(KeyEvent e); }