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This is a backport of OpenJFX 8 to run on Java 7.
The newest version!
/*
* Copyright (c) 2010, 2013, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
package javafx.beans.binding;
import javafx.beans.InvalidationListener;
import javafx.beans.Observable;
import javafx.beans.value.ChangeListener;
import javafx.collections.FXCollections;
import javafx.collections.ObservableList;
import com.sun.javafx.collections.annotations.ReturnsUnmodifiableCollection;
import com.sun.javafx.binding.BindingHelperObserver;
import com.sun.javafx.binding.ExpressionHelper;
/**
* Base class that provides most of the functionality needed to implement a
* {@link Binding} of a {@code double} value.
*
* {@code DoubleBinding} provides a simple invalidation-scheme. An extending
* class can register dependencies by calling {@link #bind(Observable...)}.
* If One of the registered dependencies becomes invalid, this
* {@code DoubleBinding} is marked as invalid. With
* {@link #unbind(Observable...)} listening to dependencies can be stopped.
*
* To provide a concrete implementation of this class, the method
* {@link #computeValue()} has to be implemented to calculate the value of this
* binding based on the current state of the dependencies. It is called when
* {@link #get()} is called for an invalid binding.
*
* Below is a simple example of a {@code DoubleBinding} calculating the square-
* root of a {@link javafx.beans.value.ObservableNumberValue} {@code moo}.
*
*
*
* final ObservableDoubleValue moo = ...;
*
* DoubleBinding foo = new DoubleBinding() {
*
* {
* super.bind(moo);
* }
*
* @Override
* protected double computeValue() {
* return Math.sqrt(moo.getValue());
* }
* };
*
*
*
* Following is the same example with implementations for the optional methods
* {@link Binding#getDependencies()} and {@link Binding#dispose()}.
*
*
*
* final ObservableDoubleValue moo = ...;
*
* DoubleBinding foo = new DoubleBinding() {
*
* {
* super.bind(moo);
* }
*
* @Override
* protected double computeValue() {
* return Math.sqrt(moo.getValue());
* }
*
* @Override
* public ObservableList getDependencies() {
* return FXCollections.singletonObservableList(moo);
* }
*
* @Override
* public void dispose() {
* super.unbind(moo);
* }
* };
*
*
*
* @see Binding
* @see NumberBinding
* @see javafx.beans.binding.DoubleExpression
*
*
* @since JavaFX 2.0
*/
public abstract class DoubleBinding extends DoubleExpression implements
NumberBinding {
private double value;
private boolean valid;
private BindingHelperObserver observer;
private ExpressionHelper helper = null;
@Override
public void addListener(InvalidationListener listener) {
helper = ExpressionHelper.addListener(helper, this, listener);
}
@Override
public void removeListener(InvalidationListener listener) {
helper = ExpressionHelper.removeListener(helper, listener);
}
@Override
public void addListener(ChangeListener listener) {
helper = ExpressionHelper.addListener(helper, this, listener);
}
@Override
public void removeListener(ChangeListener listener) {
helper = ExpressionHelper.removeListener(helper, listener);
}
/**
* Start observing the dependencies for changes. If the value of one of the
* dependencies changes, the binding is marked as invalid.
*
* @param dependencies
* the dependencies to observe
*/
protected final void bind(Observable... dependencies) {
if ((dependencies != null) && (dependencies.length > 0)) {
if (observer == null) {
observer = new BindingHelperObserver(this);
}
for (final Observable dep : dependencies) {
dep.addListener(observer);
}
}
}
/**
* Stop observing the dependencies for changes.
*
* @param dependencies
* the dependencies to stop observing
*/
protected final void unbind(Observable... dependencies) {
if (observer != null) {
for (final Observable dep : dependencies) {
dep.removeListener(observer);
}
observer = null;
}
}
/**
* A default implementation of {@code dispose()} that is empty.
*/
@Override
public void dispose() {
}
/**
* A default implementation of {@code getDependencies()} that returns an
* empty {@link javafx.collections.ObservableList}.
*
* @return an empty {@code ObservableList}
*/
@Override
@ReturnsUnmodifiableCollection
public ObservableList getDependencies() {
return FXCollections.emptyObservableList();
}
/**
* Returns the result of {@link #computeValue()}. The method
* {@code computeValue()} is only called if the binding is invalid. The
* result is cached and returned if the binding did not become invalid since
* the last call of {@code get()}.
*
* @return the current value
*/
@Override
public final double get() {
if (!valid) {
value = computeValue();
valid = true;
}
return value;
}
/**
* The method onInvalidating() can be overridden by extending classes to
* react, if this binding becomes invalid. The default implementation is
* empty.
*/
protected void onInvalidating() {
}
@Override
public final void invalidate() {
if (valid) {
valid = false;
onInvalidating();
ExpressionHelper.fireValueChangedEvent(helper);
}
}
@Override
public final boolean isValid() {
return valid;
}
/**
* Calculates the current value of this binding.
*
* Classes extending {@code DoubleBinding} have to provide an implementation
* of {@code computeValue}.
*
* @return the current value
*/
protected abstract double computeValue();
/**
* Returns a string representation of this {@code DoubleBinding} object.
* @return a string representation of this {@code DoubleBinding} object.
*/
@Override
public String toString() {
return valid ? "DoubleBinding [value: " + get() + "]"
: "DoubleBinding [invalid]";
}
}