Top Description Methods
javafx.beans

public Interface Observable

Known Direct Subinterfaces
javafx.beans.value.ObservableValue, javafx.collections.ObservableArray, javafx.collections.ObservableList, javafx.collections.ObservableMap, javafx.collections.ObservableSet
Imports
java.util.Objects, javafx.util.Subscription
An Observable is an entity that wraps content and allows to observe the content for invalidations.

An implementation of Observable may support lazy evaluation, which means that the content is not immediately recomputed after changes, but lazily the next time it is requested. All bindings and properties in this library support lazy evaluation.

Implementations of this class should strive to generate as few events as possible to avoid wasting too much time in event handlers. Implementations in this library mark themselves as invalid when the first invalidation event occurs. They do not generate anymore invalidation events until their value is recomputed and valid again.

Since
JavaFX 2.0
See Also
javafx.beans.value.ObservableValue, javafx.collections.ObservableList, javafx.collections.ObservableMap

Method Summary

Modifier and TypeMethod and Description
public void
addListener(InvalidationListener
The listener to register
listener)

Adds an InvalidationListener which will be notified whenever the Observable becomes invalid.

public void
removeListener(InvalidationListener
The listener to remove
listener)

Removes the given listener from the list of listeners, that are notified whenever the value of the Observable becomes invalid.

public default Subscription

Returns:

a Subscription which can be used to cancel this subscription, never null
subscribe(Runnable
a Runnable to call whenever this value becomes invalid, cannot be null
invalidationSubscriber)

Creates a Subscription on this Observable which calls invalidationSubscriber whenever it becomes invalid.

Method Detail

addListenerback to summary
public void addListener(InvalidationListener listener)

Adds an InvalidationListener which will be notified whenever the Observable becomes invalid. If the same listener is added more than once, then it will be notified more than once. That is, no check is made to ensure uniqueness.

Note that the same actual InvalidationListener instance may be safely registered for different Observables.

The Observable stores a strong reference to the listener which will prevent the listener from being garbage collected and may result in a memory leak. It is recommended to either unregister a listener by calling removeListener after use or to use an instance of WeakInvalidationListener avoid this situation.

Parameters
listener:InvalidationListener

The listener to register

Exceptions
NullPointerException:
if the listener is null
See Also
removeListener(InvalidationListener)
removeListenerback to summary
public void removeListener(InvalidationListener listener)

Removes the given listener from the list of listeners, that are notified whenever the value of the Observable becomes invalid.

If the given listener has not been previously registered (i.e. it was never added) then this method call is a no-op. If it had been previously added then it will be removed. If it had been added more than once, then only the first occurrence will be removed.

Parameters
listener:InvalidationListener

The listener to remove

Exceptions
NullPointerException:
if the listener is null
See Also
addListener(InvalidationListener)
subscribeback to summary
public default Subscription subscribe(Runnable invalidationSubscriber)

Creates a Subscription on this Observable which calls invalidationSubscriber whenever it becomes invalid. The provided subscriber is akin to an InvalidationListener without the Observable parameter. If the same subscriber is subscribed more than once, then it will be notified more than once. That is, no check is made to ensure uniqueness.

Note that the same subscriber instance may be safely subscribed for different Observables.

Also note that when subscribing on an Observable with a longer lifecycle than the subscriber, the subscriber must be unsubscribed when no longer needed as the subscription will otherwise keep the subscriber from being garbage collected.

Parameters
invalidationSubscriber:Runnable

a Runnable to call whenever this value becomes invalid, cannot be null

Returns:Subscription

a Subscription which can be used to cancel this subscription, never null

Exceptions
NullPointerException:
if the subscriber is null
Since
21
See Also
addListener(InvalidationListener)