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/*
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* Copyright (c) 1999, 2014, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package javax.swing;
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import java.beans.PropertyChangeEvent;
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import java.beans.PropertyChangeListener;
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import java.io.*;
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import java.lang.ref.WeakReference;
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import java.lang.ref.ReferenceQueue;
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/**
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* A package-private PropertyChangeListener which listens for
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* property changes on an Action and updates the properties
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* of an ActionEvent source.
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* <p>
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* Subclasses must override the actionPropertyChanged method,
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* which is invoked from the propertyChange method as long as
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* the target is still valid.
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* </p>
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* <p>
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* WARNING WARNING WARNING WARNING WARNING WARNING:<br>
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* Do NOT create an annonymous inner class that extends this! If you do
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* a strong reference will be held to the containing class, which in most
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* cases defeats the purpose of this class.
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*
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* @param T the type of JComponent the underlying Action is attached to
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*
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* @author Georges Saab
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* @see AbstractButton
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*/
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@SuppressWarnings("serial") // Bound of type variable is not serializable across versions
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abstract class ActionPropertyChangeListener<T extends JComponent>
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implements PropertyChangeListener, Serializable {
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private static ReferenceQueue<JComponent> queue;
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// WeakReference's aren't serializable.
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private transient OwnedWeakReference<T> target;
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// The Component's that reference an Action do so through a strong
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// reference, so that there is no need to check for serialized.
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private Action action;
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private static ReferenceQueue<JComponent> getQueue() {
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synchronized(ActionPropertyChangeListener.class) {
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if (queue == null) {
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queue = new ReferenceQueue<JComponent>();
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}
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}
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return queue;
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}
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public ActionPropertyChangeListener(T c, Action a) {
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super();
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setTarget(c);
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this.action = a;
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}
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/**
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* PropertyChangeListener method. If the target has been gc'ed this
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* will remove the <code>PropertyChangeListener</code> from the Action,
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* otherwise this will invoke actionPropertyChanged.
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*/
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public final void propertyChange(PropertyChangeEvent e) {
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T target = getTarget();
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if (target == null) {
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getAction().removePropertyChangeListener(this);
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} else {
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actionPropertyChanged(target, getAction(), e);
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}
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}
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/**
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* Invoked when a property changes on the Action and the target
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* still exists.
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*/
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protected abstract void actionPropertyChanged(T target, Action action,
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PropertyChangeEvent e);
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private void setTarget(T c) {
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ReferenceQueue<JComponent> queue = getQueue();
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// Check to see whether any old buttons have
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// been enqueued for GC. If so, look up their
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// PCL instance and remove it from its Action.
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OwnedWeakReference<?> r;
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while ((r = (OwnedWeakReference)queue.poll()) != null) {
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ActionPropertyChangeListener<?> oldPCL = r.getOwner();
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Action oldAction = oldPCL.getAction();
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if (oldAction!=null) {
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oldAction.removePropertyChangeListener(oldPCL);
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}
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}
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this.target = new OwnedWeakReference<T>(c, queue, this);
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}
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public T getTarget() {
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if (target == null) {
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// Will only happen if serialized and real target was null
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return null;
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}
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return this.target.get();
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}
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public Action getAction() {
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return action;
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}
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private void writeObject(ObjectOutputStream s) throws IOException {
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s.defaultWriteObject();
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s.writeObject(getTarget());
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}
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@SuppressWarnings("unchecked")
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private void readObject(ObjectInputStream s)
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throws IOException, ClassNotFoundException {
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s.defaultReadObject();
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T target = (T)s.readObject();
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if (target != null) {
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setTarget(target);
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}
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}
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private static class OwnedWeakReference<U extends JComponent> extends
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WeakReference<U> {
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private ActionPropertyChangeListener<?> owner;
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OwnedWeakReference(U target, ReferenceQueue<? super U> queue,
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ActionPropertyChangeListener<?> owner) {
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super(target, queue);
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this.owner = owner;
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}
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public ActionPropertyChangeListener<?> getOwner() {
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return owner;
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}
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}
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}
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