Source code

001/*
002 * Copyright (c) 2010, 2013, Oracle and/or its affiliates. All rights reserved.
003 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
004 *
005 * This code is free software; you can redistribute it and/or modify it
006 * under the terms of the GNU General Public License version 2 only, as
007 * published by the Free Software Foundation.  Oracle designates this
008 * particular file as subject to the "Classpath" exception as provided
009 * by Oracle in the LICENSE file that accompanied this code.
010 *
011 * This code is distributed in the hope that it will be useful, but WITHOUT
012 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
013 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
014 * version 2 for more details (a copy is included in the LICENSE file that
015 * accompanied this code).
016 *
017 * You should have received a copy of the GNU General Public License version
018 * 2 along with this work; if not, write to the Free Software Foundation,
019 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
020 *
021 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
022 * or visit www.oracle.com if you need additional information or have any
023 * questions.
024 */
025
026package javafx.beans.binding;
027
028import javafx.beans.value.ObservableValue;
029import javafx.collections.ObservableList;
030import com.sun.javafx.collections.annotations.ReturnsUnmodifiableCollection;
031
032/**
033 * A {@code Binding} calculates a value that depends on one or more sources. The
034 * sources are usually called the dependency of a binding. A binding observes
035 * its dependencies for changes and updates its value automatically.
036 * <p>
037 * While a dependency of a binding can be anything, it is almost always an
038 * implementation of {@link javafx.beans.value.ObservableValue}. {@code Binding}
039 * implements {@code ObservableValue} allowing to use it in another binding.
040 * With that one can assemble very complex bindings from simple bindings.
041 * <p>
042 * All bindings in the JavaFX 2.0 runtime are calculated lazily. That means, if
043 * a dependency changes, the result of a binding is not immediately
044 * recalculated, but it is marked as invalid. Next time the value of an invalid
045 * binding is requested, it is recalculated.
046 * <p>
047 * It is recommended to use one of the base classes defined in this package
048 * (e.g. {@link DoubleBinding}) to define a custom binding, because these
049 * classes already provide most of the needed functionality. See
050 * {@link DoubleBinding} for an example.
051 * 
052 * @see DoubleBinding
053 * 
054 * 
055 */
056public interface Binding<T> extends ObservableValue<T> {
057
058    /**
059     * Checks if a binding is valid.
060     * 
061     * @return {@code true} if the {@code Binding} is valid, {@code false}
062     *         otherwise
063     */
064    boolean isValid();
065
066    /**
067     * Mark a binding as invalid. This forces the recalculation of the value of
068     * the {@code Binding} next time it is request.
069     */
070    void invalidate();
071
072    /**
073     * Returns the dependencies of a binding in an unmodifiable
074     * {@link javafx.collections.ObservableList}. The implementation is
075     * optional. The main purpose of this method is to support developers during
076     * development. It allows to explore and monitor dependencies of a binding
077     * during runtime.
078     * <p>
079     * Because this method should not be used in production code, it is
080     * recommended to implement this functionality as sparse as possible. For
081     * example if the dependencies do not change, each call can generate a new
082     * {@code ObservableList}, avoiding the necessity to store the result.
083     * 
084     * @return an unmodifiable {@code} ObservableList of the dependencies
085     */
086    @ReturnsUnmodifiableCollection
087    ObservableList<?> getDependencies();
088
089    /**
090     * Signals to the {@code Binding} that it will not be used anymore and any
091     * references can be removed. A call of this method usually results in the
092     * binding stopping to observe its dependencies by unregistering its
093     * listener(s). The implementation is optional.
094     * <p>
095     * All bindings in our implementation use instances of
096     * {@link javafx.beans.WeakInvalidationListener}, which means usually
097     * a binding does not need to be disposed. But if you plan to use your
098     * application in environments that do not support {@code WeakReferences}
099     * you have to dispose unused {@code Bindings} to avoid memory leaks.
100     */
101    void dispose();
102
103}