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Java > Open Source Codes > javax > swing > plaf > UIResource


1 /*
2  * @(#)UIResource.java 1.10 03/12/19
3  *
4  * Copyright 2004 Sun Microsystems, Inc. All rights reserved.
5  * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
6  */
7
8 package javax.swing.plaf;
9
10
11 /**
12  * This interface is used to mark objects created by ComponentUI delegates.
13  * The <code>ComponentUI.installUI()</code> and
14  * <code>ComponentUI.uninstallUI()</code> methods can use this interface
15  * to decide if a properties value has been overridden. For example, the
16  * JList cellRenderer property is initialized by BasicListUI.installUI(),
17  * only if it's initial value is null:
18  * <pre>
19  * if (list.getCellRenderer() == null) {
20  * list.setCellRenderer((ListCellRenderer)(UIManager.get("List.cellRenderer")));
21  * }
22  * </pre>
23  * At uninstallUI() time we reset the property to null if its value
24  * is an instance of UIResource:
25  * <pre>
26  * if (list.getCellRenderer() instanceof UIResource) {
27  * list.setCellRenderer(null);
28  * }
29  *</pre>
30  * This pattern applies to all properties except the java.awt.Component
31  * properties font, foreground, and background. If one of these
32  * properties isn't initialized, or is explicitly set to null,
33  * its container provides the value. For this reason the
34  * <code>"== null"</code> is unreliable when installUI() is called
35  * to dynamically change a components look and feel. So at installUI()
36  * time we check to see if the current value is a UIResource:
37  *<pre>
38  * if (!(list.getFont() instanceof UIResource)) {
39  * list.setFont(UIManager.getFont("List.font"));
40  * }
41  * </pre>
42  *
43  * @see ComponentUI
44  * @version 1.10 12/19/03
45  * @author Hans Muller
46  *
47  */
48
49 public interface UIResource {
50 }
51
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