/*
* Copyright (c) 2011, 2013, Oracle and/or its affiliates. All rights reserved.
* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*
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package javafx.collections;
import javafx.beans.
NamedArg;
import javafx.beans.
WeakListener;
import java.lang.ref.
WeakReference;
/**
* A {@code WeakMapChangeListener} can be used, if an {@link javafx.collections.ObservableMap}
* should only maintain a weak reference to the listener. This helps to avoid
* memory leaks, that can occur if observers are not unregistered from observed
* objects after use.
* <p>
* {@code WeakMapChangeListener} are created by passing in the original
* {@link javafx.collections.MapChangeListener}. The {@code WeakMapChangeListener} should then be
* registered to listen for changes of the observed object.
* <p>
* Note: You have to keep a reference to the {@code MapChangeListener}, that
* was passed in as long as it is in use, otherwise it will be garbage collected
* to soon.
*
* @see MapChangeListener
* @see ObservableMap
* @see javafx.beans.WeakListener
*
* @param <K> the key element type
* @param <V> the value element type
*
* @since JavaFX 2.1
*/
public final class
WeakMapChangeListener<K, V> implements
MapChangeListener<K, V>,
WeakListener {
private final
WeakReference<
MapChangeListener<K, V>>
ref;
/**
* The constructor of {@code WeakMapChangeListener}.
*
* @param listener
* The original listener that should be notified
*/
public
WeakMapChangeListener(@
NamedArg("listener")
MapChangeListener<K, V>
listener) {
if (
listener == null) {
throw new
NullPointerException("Listener must be specified.");
}
this.
ref = new
WeakReference<
MapChangeListener<K, V>>(
listener);
}
/**
* {@inheritDoc}
*/
@
Override
public boolean
wasGarbageCollected() {
return (
ref.
get() == null);
}
/**
* {@inheritDoc}
*/
@
Override
public void
onChanged(
Change<? extends K,? extends V>
change) {
final
MapChangeListener<K, V>
listener =
ref.
get();
if (
listener != null) {
listener.
onChanged(
change);
} else {
// The weakly reference listener has been garbage collected,
// so this WeakListener will now unhook itself from the
// source bean
change.
getMap().
removeListener(this);
}
}
}