org.eclipse.jface.util.PropertyChangeEvent Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of org.eclipse.jface Show documentation
This is org.eclipse.jface jar used by Scout SDK
The newest version!
/*******************************************************************************
 * Copyright (c) 2000, 2015 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.jface.util;

import java.util.EventObject;
import org.eclipse.core.runtime.Assert;

/**
 * An event object describing a change to a named property.
 * 
 * This concrete class was designed to be instantiated, but may
 * also be subclassed if required.
 * 
 * 
 * The JFace frameworks contain classes that report property
 * change events for internal state changes that may be of interest
 * to external parties. A special listener interface
 * (IPropertyChangeListener) is defined for this purpose,
 * and a typical class allow listeners to be registered via
 * an addPropertyChangeListener method.
 * 
 *
 * @see IPropertyChangeListener
 */
public class PropertyChangeEvent extends EventObject {

    /**
     * Generated serial version UID for this class.
     * @since 3.1
     */
    private static final long serialVersionUID = 3256726173533811256L;

    /**
     * The name of the changed property.
     */
    private String propertyName;

    /**
     * The old value of the changed property, or null if
     * not known or not relevant.
     */
    private Object oldValue;

    /**
     * The new value of the changed property, or null if
     * not known or not relevant.
     */
    private Object newValue;

    /**
     * Creates a new property change event.
     *
     * @param source the object whose property has changed
     * @param property the property that has changed (must not be null)
     * @param oldValue the old value of the property, or null if none
     * @param newValue the new value of the property, or null if none
     */
    public PropertyChangeEvent(Object source, String property, Object oldValue,
            Object newValue) {
        super(source);
        Assert.isNotNull(property);
        this.propertyName = property;
        this.oldValue = oldValue;
        this.newValue = newValue;
    }

    /**
     * Returns the new value of the property.
     *
     * @return the new value, or null if not known
     *  or not relevant (for instance if the property was removed).
     */
    public Object getNewValue() {
        return newValue;
    }

    /**
     * Returns the old value of the property.
     *
     * @return the old value, or null if not known
     *  or not relevant (for instance if the property was just
     *  added and there was no old value).
     */
    public Object getOldValue() {
        return oldValue;
    }

    /**
     * Returns the name of the property that changed.
     * 
     * Warning: there is no guarantee that the property name returned
     * is a constant string.  Callers must compare property names using
     * equals, not ==.
     * 
     *
     * @return the name of the property that changed
     */
    public String getProperty() {
        return propertyName;
    }
}