JDK8/Java8源码在线阅读

/*
 * Copyright (c) 2003, 2011, 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 sun.awt;

import java.awt.event.FocusEvent;
import java.awt.Component;

/**
 * This class represents FocusEvents with a known "cause" - reason why this event happened. It can
 * be mouse press, traversal, activation, and so on - all causes are described as Cause enum. The
 * event with the cause can be constructed in two ways - explicitly through constructor of
 * CausedFocusEvent class or implicitly, by calling appropriate requestFocusXXX method with "cause"
 * parameter. The default cause is UNKNOWN.
 */
@SuppressWarnings("serial")
public class CausedFocusEvent extends FocusEvent {
    public enum Cause {
        UNKNOWN,
        MOUSE_EVENT,
        TRAVERSAL,
        TRAVERSAL_UP,
        TRAVERSAL_DOWN,
        TRAVERSAL_FORWARD,
        TRAVERSAL_BACKWARD,
        MANUAL_REQUEST,
        AUTOMATIC_TRAVERSE,
        ROLLBACK,
        NATIVE_SYSTEM,
        ACTIVATION,
        CLEAR_GLOBAL_FOCUS_OWNER,
        RETARGETED
    };

    private final Cause cause;

    public Cause getCause() {
        return cause;
    }

    public String toString() {
        return "java.awt.FocusEvent[" + super.paramString() + ",cause=" + cause + "] on " + getSource();
    }

    public CausedFocusEvent(Component source, int id, boolean temporary,
                            Component opposite, Cause cause) {
        super(source, id, temporary, opposite);
        if (cause == null) {
            cause = Cause.UNKNOWN;
        }
        this.cause = cause;
    }

    /**
     * Retargets the original focus event to the new target.  If the
     * original focus event is CausedFocusEvent, it remains such and
     * cause is copied.  Otherwise, new CausedFocusEvent is created,
     * with cause as RETARGETED.
     * @return retargeted event, or null if e is null
     */

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