javafx.beans.value

Class WeakChangeListener<T>

java.lang.Object

javafx.beans.value.WeakChangeListener<T>

Type Parameters:

T - The type of the observed value

All Implemented Interfaces:

ChangeListener<T>

public final class WeakChangeListener<T>
extends java.lang.Object
implements ChangeListener<T>

A WeakChangeListener can be used if an ObservableValue should only maintain a weak reference to the listener. This helps to avoid memory leaks which can occur if observers are not unregistered from observed objects after use.

WeakChangeListener instances are created by passing in the original ChangeListener. The WeakChangeListener should then be registered to listen for changes of the observed object.

Note: You have to keep a reference to the ChangeListener that was passed in for as long as it is in use, otherwise it will be garbage collected too soon.

Since:

JavaFX 2.0

See Also:

ChangeListener, ObservableValue

Field Summary

Fields

Modifier and Type	Field and Description
private java.lang.ref.WeakReference<ChangeListener<T>>	ref

Constructor Summary

Constructors

Constructor and Description
WeakChangeListener(ChangeListener<T> listener) The constructor of WeakChangeListener.

Method Summary

Modifier and Type	Method and Description
void	changed(ObservableValue<? extends T> observable, T oldValue, T newValue) This method needs to be provided by an implementation of ChangeListener.
boolean	wasGarbageCollected()

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

ref

private final java.lang.ref.WeakReference<ChangeListener<T>> ref

Constructor Detail

WeakChangeListener

public WeakChangeListener(ChangeListener<T> listener)

The constructor of WeakChangeListener.

Parameters:

listener - The original listener that should be notified

Method Detail

wasGarbageCollected

public boolean wasGarbageCollected()

changed

public void changed(ObservableValue<? extends T> observable,
                    T oldValue,
                    T newValue)

This method needs to be provided by an implementation of ChangeListener. It is called if the value of an ObservableValue changes.

In general, it is considered bad practice to modify the observed value in this method.

Specified by:

changed in interface ChangeListener<T>

Parameters:

observable - The ObservableValue which value changed

oldValue - The old value

newValue - The new value