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| 1 | /* | ||
| 2 | * Copyright (c) 2000, 2005, 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 | /** | ||
| 28 | * A FocusTraversalPolicy defines the order in which Components with a | ||
| 29 | * particular focus cycle root are traversed. Instances can apply the policy to | ||
| 30 | * arbitrary focus cycle roots, allowing themselves to be shared across | ||
| 31 | * Containers. They do not need to be reinitialized when the focus cycle roots | ||
| 32 | * of a Component hierarchy change. | ||
| 33 | * <p> | ||
| 34 | * The core responsibility of a FocusTraversalPolicy is to provide algorithms | ||
| 35 | * determining the next and previous Components to focus when traversing | ||
| 36 | * forward or backward in a UI. Each FocusTraversalPolicy must also provide | ||
| 37 | * algorithms for determining the first, last, and default Components in a | ||
| 38 | * traversal cycle. First and last Components are used when normal forward and | ||
| 39 | * backward traversal, respectively, wraps. The default Component is the first | ||
| 40 | * to receive focus when traversing down into a new focus traversal cycle. | ||
| 41 | * A FocusTraversalPolicy can optionally provide an algorithm for determining | ||
| 42 | * a Window's initial Component. The initial Component is the first to receive | ||
| 43 | * focus when a Window is first made visible. | ||
| 44 | * <p> | ||
| 45 | * FocusTraversalPolicy takes into account <a | ||
| 46 | * href="doc-files/FocusSpec.html#FocusTraversalPolicyProviders">focus traversal | ||
| 47 | * policy providers</a>. When searching for first/last/next/previous Component, | ||
| 48 | * if a focus traversal policy provider is encountered, its focus traversal | ||
| 49 | * policy is used to perform the search operation. | ||
| 50 | * <p> | ||
| 51 | * Please see | ||
| 52 | * <a href="http://java.sun.com/docs/books/tutorial/uiswing/misc/focus.html"> | ||
| 53 | * How to Use the Focus Subsystem</a>, | ||
| 54 | * a section in <em>The Java Tutorial</em>, and the | ||
| 55 | * <a href="../../java/awt/doc-files/FocusSpec.html">Focus Specification</a> | ||
| 56 | * for more information. | ||
| 57 | * | ||
| 58 | * @author David Mendenhall | ||
| 59 | * | ||
| 60 | * @see Container#setFocusTraversalPolicy | ||
| 61 | * @see Container#getFocusTraversalPolicy | ||
| 62 | * @see Container#setFocusCycleRoot | ||
| 63 | * @see Container#isFocusCycleRoot | ||
| 64 | * @see Container#setFocusTraversalPolicyProvider | ||
| 65 | * @see Container#isFocusTraversalPolicyProvider | ||
| 66 | * @see KeyboardFocusManager#setDefaultFocusTraversalPolicy | ||
| 67 | * @see KeyboardFocusManager#getDefaultFocusTraversalPolicy | ||
| 68 | * @since 1.4 | ||
| 69 | */ | ||
| 70 | public abstract class FocusTraversalPolicy { | ||
| 71 | |||
| 72 | /** | ||
| 73 | * Returns the Component that should receive the focus after aComponent. | ||
| 74 | * aContainer must be a focus cycle root of aComponent or a focus traversal | ||
| 75 | * policy provider. | ||
| 76 | * | ||
| 77 | * @param aContainer a focus cycle root of aComponent or focus traversal | ||
| 78 | * policy provider | ||
| 79 | * @param aComponent a (possibly indirect) child of aContainer, or | ||
| 80 | * aContainer itself | ||
| 81 | * @return the Component that should receive the focus after aComponent, or | ||
| 82 | * null if no suitable Component can be found | ||
| 83 | * @throws IllegalArgumentException if aContainer is not a focus cycle | ||
| 84 | * root of aComponent or a focus traversal policy provider, or if | ||
| 85 | * either aContainer or aComponent is null | ||
| 86 | */ | ||
| 87 | public abstract Component getComponentAfter(Container aContainer, | ||
| 88 | Component aComponent); | ||
| 89 | |||
| 90 | /** | ||
| 91 | * Returns the Component that should receive the focus before aComponent. | ||
| 92 | * aContainer must be a focus cycle root of aComponent or a focus traversal | ||
| 93 | * policy provider. | ||
| 94 | * | ||
| 95 | * @param aContainer a focus cycle root of aComponent or focus traversal | ||
| 96 | * policy provider | ||
| 97 | * @param aComponent a (possibly indirect) child of aContainer, or | ||
| 98 | * aContainer itself | ||
| 99 | * @return the Component that should receive the focus before aComponent, | ||
| 100 | * or null if no suitable Component can be found | ||
| 101 | * @throws IllegalArgumentException if aContainer is not a focus cycle | ||
| 102 | * root of aComponent or a focus traversal policy provider, or if | ||
| 103 | * either aContainer or aComponent is null | ||
| 104 | */ | ||
| 105 | public abstract Component getComponentBefore(Container aContainer, | ||
| 106 | Component aComponent); | ||
| 107 | |||
| 108 | /** | ||
| 109 | * Returns the first Component in the traversal cycle. This method is used | ||
| 110 | * to determine the next Component to focus when traversal wraps in the | ||
| 111 | * forward direction. | ||
| 112 | * | ||
| 113 | * @param aContainer the focus cycle root or focus traversal policy provider | ||
| 114 | * whose first Component is to be returned | ||
| 115 | * @return the first Component in the traversal cycle of aContainer, | ||
| 116 | * or null if no suitable Component can be found | ||
| 117 | * @throws IllegalArgumentException if aContainer is null | ||
| 118 | */ | ||
| 119 | public abstract Component getFirstComponent(Container aContainer); | ||
| 120 | |||
| 121 | /** | ||
| 122 | * Returns the last Component in the traversal cycle. This method is used | ||
| 123 | * to determine the next Component to focus when traversal wraps in the | ||
| 124 | * reverse direction. | ||
| 125 | * | ||
| 126 | * @param aContainer the focus cycle root or focus traversal policy | ||
| 127 | * provider whose last Component is to be returned | ||
| 128 | * @return the last Component in the traversal cycle of aContainer, | ||
| 129 | * or null if no suitable Component can be found | ||
| 130 | * @throws IllegalArgumentException if aContainer is null | ||
| 131 | */ | ||
| 132 | public abstract Component getLastComponent(Container aContainer); | ||
| 133 | |||
| 134 | /** | ||
| 135 | * Returns the default Component to focus. This Component will be the first | ||
| 136 | * to receive focus when traversing down into a new focus traversal cycle | ||
| 137 | * rooted at aContainer. | ||
| 138 | * | ||
| 139 | * @param aContainer the focus cycle root or focus traversal policy | ||
| 140 | * provider whose default Component is to be returned | ||
| 141 | * @return the default Component in the traversal cycle of aContainer, | ||
| 142 | * or null if no suitable Component can be found | ||
| 143 | * @throws IllegalArgumentException if aContainer is null | ||
| 144 | */ | ||
| 145 | public abstract Component getDefaultComponent(Container aContainer); | ||
| 146 | |||
| 147 | /** | ||
| 148 | * Returns the Component that should receive the focus when a Window is | ||
| 149 | * made visible for the first time. Once the Window has been made visible | ||
| 150 | * by a call to <code>show()</code> or <code>setVisible(true)</code>, the | ||
| 151 | * initial Component will not be used again. Instead, if the Window loses | ||
| 152 | * and subsequently regains focus, or is made invisible or undisplayable | ||
| 153 | * and subsequently made visible and displayable, the Window's most | ||
| 154 | * recently focused Component will become the focus owner. The default | ||
| 155 | * implementation of this method returns the default Component. | ||
| 156 | * | ||
| 157 | * @param window the Window whose initial Component is to be returned | ||
| 158 | * @return the Component that should receive the focus when window is made | ||
| 159 | * visible for the first time, or null if no suitable Component can | ||
| 160 | * be found | ||
| 161 | * @see #getDefaultComponent | ||
| 162 | * @see Window#getMostRecentFocusOwner | ||
| 163 | * @throws IllegalArgumentException if window is null | ||
| 164 | */ | ||
| 165 | public Component getInitialComponent(Window window) { | ||
| 166 | if ( window == null ){ | ||
| 167 | throw new IllegalArgumentException("window cannot be equal to null."); | ||
| 168 | } | ||
| 169 | Component def = getDefaultComponent(window); | ||
| 170 | if (def == null && window.isFocusableWindow()) { | ||
| 171 | def = window; | ||
| 172 | } | ||
| 173 | return def; | ||
| 174 | } | ||
| 175 | } | ||