WeakInvalidationListener (JavaFX 11)

java.lang.Object
- javafx.beans.WeakInvalidationListener

All Implemented Interfaces:

InvalidationListener, WeakListener
```
public final class WeakInvalidationListener
extends Object
implements InvalidationListener, WeakListener
```
A WeakInvalidationListener can be used if an Observable 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.
A WeakInvalidationListener is created by passing in the original InvalidationListener. The WeakInvalidationListener should then be registered to listen for changes of the observed object.
Note: You have to keep a reference to the InvalidationListener that was passed in as long as it is in use, otherwise it can be garbage collected too soon.

Since:

JavaFX 2.0

See Also:

InvalidationListener, Observable

Constructor Summary

Constructors
Constructor Description

WeakInvalidationListener(InvalidationListener listener)
The constructor of WeakInvalidationListener.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`void`	`invalidated(Observable observable)`	This method needs to be provided by an implementation of `InvalidationListener`.
`boolean`	`wasGarbageCollected()`	Returns `true` if the linked listener was garbage-collected.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Constructor Detail
  - WeakInvalidationListener
```
public WeakInvalidationListener(InvalidationListener listener)
```
    The constructor of WeakInvalidationListener.
    
    Parameters:
    
    listener - The original listener that should be notified
- Method Detail
  - wasGarbageCollected
```
public boolean wasGarbageCollected()
```
    Returns true if the linked listener was garbage-collected. In this case, the listener can be removed from the observable.
    
    Specified by:
    
    wasGarbageCollected in interface WeakListener
    
    Returns:
    
    true if the linked listener was garbage-collected.
  - invalidated
```
public void invalidated(Observable observable)
```
    This method needs to be provided by an implementation of InvalidationListener. It is called if an Observable becomes invalid.
    In general, it is considered bad practice to modify the observed value in this method.
    
    Specified by:
    
    invalidated in interface InvalidationListener
    
    Parameters:
    
    observable - The Observable that became invalid