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| 1 | +/* | |
| 2 | + * Copyright (c) 2000, 2004, 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 | +package java.awt; | |
| 26 | + | |
| 27 | +import java.awt.peer.ComponentPeer; | |
| 28 | + | |
| 29 | + | |
| 30 | +/** | |
| 31 | + * A FocusTraversalPolicy that determines traversal order based on the order | |
| 32 | + * of child Components in a Container. From a particular focus cycle root, the | |
| 33 | + * policy makes a pre-order traversal of the Component hierarchy, and traverses | |
| 34 | + * a Container's children according to the ordering of the array returned by | |
| 35 | + * <code>Container.getComponents()</code>. Portions of the hierarchy that are | |
| 36 | + * not visible and displayable will not be searched. | |
| 37 | + * <p> | |
| 38 | + * If client code has explicitly set the focusability of a Component by either | |
| 39 | + * overriding <code>Component.isFocusTraversable()</code> or | |
| 40 | + * <code>Component.isFocusable()</code>, or by calling | |
| 41 | + * <code>Component.setFocusable()</code>, then a DefaultFocusTraversalPolicy | |
| 42 | + * behaves exactly like a ContainerOrderFocusTraversalPolicy. If, however, the | |
| 43 | + * Component is relying on default focusability, then a | |
| 44 | + * DefaultFocusTraversalPolicy will reject all Components with non-focusable | |
| 45 | + * peers. This is the default FocusTraversalPolicy for all AWT Containers. | |
| 46 | + * <p> | |
| 47 | + * The focusability of a peer is implementation-dependent. Sun recommends that | |
| 48 | + * all implementations for a particular native platform construct peers with | |
| 49 | + * the same focusability. The recommendations for Windows and Unix are that | |
| 50 | + * Canvases, Labels, Panels, Scrollbars, ScrollPanes, Windows, and lightweight | |
| 51 | + * Components have non-focusable peers, and all other Components have focusable | |
| 52 | + * peers. These recommendations are used in the Sun AWT implementations. Note | |
| 53 | + * that the focusability of a Component's peer is different from, and does not | |
| 54 | + * impact, the focusability of the Component itself. | |
| 55 | + * <p> | |
| 56 | + * Please see | |
| 57 | + * <a href="http://java.sun.com/docs/books/tutorial/uiswing/misc/focus.html"> | |
| 58 | + * How to Use the Focus Subsystem</a>, | |
| 59 | + * a section in <em>The Java Tutorial</em>, and the | |
| 60 | + * <a href="../../java/awt/doc-files/FocusSpec.html">Focus Specification</a> | |
| 61 | + * for more information. | |
| 62 | + * | |
| 63 | + * @author David Mendenhall | |
| 64 | + * | |
| 65 | + * @see Container#getComponents | |
| 66 | + * @see Component#isFocusable | |
| 67 | + * @see Component#setFocusable | |
| 68 | + * @since 1.4 | |
| 69 | + */ | |
| 70 | +public class DefaultFocusTraversalPolicy | |
| 71 | + extends ContainerOrderFocusTraversalPolicy | |
| 72 | +{ | |
| 73 | + /* | |
| 74 | + * serialVersionUID | |
| 75 | + */ | |
| 76 | + private static final long serialVersionUID = 8876966522510157497L; | |
| 77 | + | |
| 78 | + /** | |
| 79 | + * Determines whether a Component is an acceptable choice as the new | |
| 80 | + * focus owner. The Component must be visible, displayable, and enabled | |
| 81 | + * to be accepted. If client code has explicitly set the focusability | |
| 82 | + * of the Component by either overriding | |
| 83 | + * <code>Component.isFocusTraversable()</code> or | |
| 84 | + * <code>Component.isFocusable()</code>, or by calling | |
| 85 | + * <code>Component.setFocusable()</code>, then the Component will be | |
| 86 | + * accepted if and only if it is focusable. If, however, the Component is | |
| 87 | + * relying on default focusability, then all Canvases, Labels, Panels, | |
| 88 | + * Scrollbars, ScrollPanes, Windows, and lightweight Components will be | |
| 89 | + * rejected. | |
| 90 | + * | |
| 91 | + * @param aComponent the Component whose fitness as a focus owner is to | |
| 92 | + * be tested | |
| 93 | + * @return <code>true</code> if aComponent meets the above requirements; | |
| 94 | + * <code>false</code> otherwise | |
| 95 | + */ | |
| 96 | + protected boolean accept(Component aComponent) { | |
| 97 | + if (!(aComponent.isVisible() && aComponent.isDisplayable() && | |
| 98 | + aComponent.isEnabled())) | |
| 99 | + { | |
| 100 | + return false; | |
| 101 | + } | |
| 102 | + | |
| 103 | + // Verify that the Component is recursively enabled. Disabling a | |
| 104 | + // heavyweight Container disables its children, whereas disabling | |
| 105 | + // a lightweight Container does not. | |
| 106 | + if (!(aComponent instanceof Window)) { | |
| 107 | + for (Container enableTest = aComponent.getParent(); | |
| 108 | + enableTest != null; | |
| 109 | + enableTest = enableTest.getParent()) | |
| 110 | + { | |
| 111 | + if (!(enableTest.isEnabled() || enableTest.isLightweight())) { | |
| 112 | + return false; | |
| 113 | + } | |
| 114 | + if (enableTest instanceof Window) { | |
| 115 | + break; | |
| 116 | + } | |
| 117 | + } | |
| 118 | + } | |
| 119 | + | |
| 120 | + boolean focusable = aComponent.isFocusable(); | |
| 121 | + if (aComponent.isFocusTraversableOverridden()) { | |
| 122 | + return focusable; | |
| 123 | + } | |
| 124 | + | |
| 125 | + ComponentPeer peer = aComponent.getPeer(); | |
| 126 | + return (peer != null && peer.isFocusable()); | |
| 127 | + } | |
| 128 | +} | |