Java tutorial
/* * Copyright (c) 1997, 1998, 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 javax.swing.plaf; /** * This interface is used to mark objects created by ComponentUI delegates. * The <code>ComponentUI.installUI()</code> and * <code>ComponentUI.uninstallUI()</code> methods can use this interface * to decide if a properties value has been overridden. For example, the * JList cellRenderer property is initialized by BasicListUI.installUI(), * only if it's initial value is null: * <pre> * if (list.getCellRenderer() == null) { * list.setCellRenderer((ListCellRenderer)(UIManager.get("List.cellRenderer"))); * } * </pre> * At uninstallUI() time we reset the property to null if its value * is an instance of UIResource: * <pre> * if (list.getCellRenderer() instanceof UIResource) { * list.setCellRenderer(null); * } *</pre> * This pattern applies to all properties except the java.awt.Component * properties font, foreground, and background. If one of these * properties isn't initialized, or is explicitly set to null, * its container provides the value. For this reason the * <code>"== null"</code> is unreliable when installUI() is called * to dynamically change a components look and feel. So at installUI() * time we check to see if the current value is a UIResource: *<pre> * if (!(list.getFont() instanceof UIResource)) { * list.setFont(UIManager.getFont("List.font")); * } * </pre> * * @see ComponentUI * @author Hans Muller * */ public interface UIResource { }