1 /*
   2  * Copyright (c) 2011, 2013, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 package javafx.beans.value;
  27 
  28 /**
  29  * A {@code ChangeListener} is notified whenever the value of an
  30  * {@link ObservableValue} changes. It can be registered and unregistered with
  31  * {@link ObservableValue#addListener(ChangeListener)} respectively
  32  * {@link ObservableValue#removeListener(ChangeListener)}
  33  * <p>
  34  * For an in-depth explanation of change events and how they differ from
  35  * invalidation events, see the documentation of {@code ObservableValue}.
  36  * <p>
  37  * The same instance of {@code ChangeListener} can be registered to listen to
  38  * multiple {@code ObservableValues}.
  39  *
  40  * @see ObservableValue
  41  *
  42  *
  43  * @since JavaFX 2.0
  44  */
  45 @FunctionalInterface
  46 public interface ChangeListener<T> {
  47 
  48     /**
  49      * This method needs to be provided by an implementation of
  50      * {@code ChangeListener}. It is called if the value of an
  51      * {@link ObservableValue} changes.
  52      * <p>
  53      * In general, it is considered bad practice to modify the observed value in
  54      * this method.
  55      *
  56      * @param observable
  57      *            The {@code ObservableValue} which value changed
  58      * @param oldValue
  59      *            The old value
  60      * @param newValue
  61      *            The new value
  62      */
  63     void changed(ObservableValue<? extends T> observable, T oldValue, T newValue);
  64 }