J. Duke | 319a3b9 | 2007-12-01 00:00:00 +0000 | [diff] [blame^] | 1 | /* |
| 2 | * Copyright 2000-2005 Sun Microsystems, Inc. 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. Sun designates this |
| 8 | * particular file as subject to the "Classpath" exception as provided |
| 9 | * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, |
| 22 | * CA 95054 USA or visit www.sun.com if you need additional information or |
| 23 | * have any 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 | } |