# Interface InvalidationListener

All Known Implementing Classes:
  `WeakInvalidationListener`

Functional Interface:
  This is a functional interface and can therefore be used as the assignment target for a lambda expression or method reference.

@FunctionalInterface public interface InvalidationListener
An `InvalidationListener` is notified whenever an `Observable` becomes invalid. It can be registered and unregistered with `Observable.addListener(InvalidationListener)` respectively `Observable.removeListener(InvalidationListener)`.

For an in-depth explanation of invalidation events and how they differ from change events, see the documentation of `ObservableValue`.

The same instance of `InvalidationListener` can be registered to listen to multiple `Observables`.

Since:
  JavaFX 2.0
See Also:
  - `Observable`
  - `ObservableValue`

- ## Method Summary

  Modifier and Type
  Method
  Description
  `void`
  `invalidated(Observable observable)`
  This method needs to be provided by an implementation of `InvalidationListener`.

- ## Method Details

  - ### invalidated

    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.

    Parameters:
      `observable` - The `Observable` that became invalid