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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 | } | ||