Spec-Zone .ru
спецификации, руководства, описания, API
001/*
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012 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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014 * version 2 for more details (a copy is included in the LICENSE file that
015 * accompanied this code).
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025
026package javafx.beans;
027
028
029/**
030 * An {@code Observable} is an entity that wraps content and allows to
031 * observe the content for invalidations.
032 * <p>
033 * An implementation of {@code Observable} may support lazy evaluation,
034 * which means that the content is not immediately recomputed after changes, but
035 * lazily the next time it is requested. All bindings and properties in
036 * this library support lazy evaluation.
037 * <p>
038 * Implementations of this class should strive to generate as few events as
039 * possible to avoid wasting too much time in event handlers. Implementations in
040 * this library mark themselves as invalid when the first invalidation event
041 * occurs. They do not generate anymore invalidation events until their value is
042 * recomputed and valid again.
043 * 
044 * @see javafx.beans.value.ObservableValue
045 * @see javafx.collections.ObservableList
046 * @see javafx.collections.ObservableMap
047 * 
048 * 
049 */
050public interface Observable {
051
052    /**
053     * Adds an {@link InvalidationListener} which will be notified whenever the
054     * {@code Observable} becomes invalid. If the same
055     * listener is added more than once, then it will be notified more than
056     * once. That is, no check is made to ensure uniqueness.
057     * <p>
058     * Note that the same actual {@code InvalidationListener} instance may be
059     * safely registered for different {@code Observables}.
060     * <p>
061     * The {@code Observable} stores a strong reference to the listener
062     * which will prevent the listener from being garbage collected and may
063     * result in a memory leak. It is recommended to either unregister a
064     * listener by calling {@link #removeListener(InvalidationListener)
065     * removeListener} after use or to use an instance of
066     * {@link WeakInvalidationListener} avoid this situation.
067     * 
068     * @see #removeListener(InvalidationListener)
069     * 
070     * @param listener
071     *            The listener to register
072     * @throws NullPointerException
073     *             if the listener is null
074     */
075    void addListener(InvalidationListener listener);
076
077    /**
078     * Removes the given listener from the list of listeners, that are notified
079     * whenever the value of the {@code Observable} becomes invalid.
080     * <p>
081     * If the given listener has not been previously registered (i.e. it was
082     * never added) then this method call is a no-op. If it had been previously
083     * added then it will be removed. If it had been added more than once, then
084     * only the first occurrence will be removed.
085     * 
086     * @see #addListener(InvalidationListener)
087     * 
088     * @param listener
089     *            The listener to remove
090     * @throws NullPointerException
091     *             if the listener is null
092     */
093    void removeListener(InvalidationListener listener);
094
095}