J. Duke | 319a3b9 | 2007-12-01 00:00:00 +0000 | [diff] [blame^] | 1 | /* |
| 2 | * Copyright 1995-2006 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 | |
| 26 | package java.awt; |
| 27 | |
| 28 | import java.util.Hashtable; |
| 29 | |
| 30 | /** |
| 31 | * A border layout lays out a container, arranging and resizing |
| 32 | * its components to fit in five regions: |
| 33 | * north, south, east, west, and center. |
| 34 | * Each region may contain no more than one component, and |
| 35 | * is identified by a corresponding constant: |
| 36 | * <code>NORTH</code>, <code>SOUTH</code>, <code>EAST</code>, |
| 37 | * <code>WEST</code>, and <code>CENTER</code>. When adding a |
| 38 | * component to a container with a border layout, use one of these |
| 39 | * five constants, for example: |
| 40 | * <pre> |
| 41 | * Panel p = new Panel(); |
| 42 | * p.setLayout(new BorderLayout()); |
| 43 | * p.add(new Button("Okay"), BorderLayout.SOUTH); |
| 44 | * </pre> |
| 45 | * As a convenience, <code>BorderLayout</code> interprets the |
| 46 | * absence of a string specification the same as the constant |
| 47 | * <code>CENTER</code>: |
| 48 | * <pre> |
| 49 | * Panel p2 = new Panel(); |
| 50 | * p2.setLayout(new BorderLayout()); |
| 51 | * p2.add(new TextArea()); // Same as p.add(new TextArea(), BorderLayout.CENTER); |
| 52 | * </pre> |
| 53 | * <p> |
| 54 | * In addition, <code>BorderLayout</code> supports the relative |
| 55 | * positioning constants, <code>PAGE_START</code>, <code>PAGE_END</code>, |
| 56 | * <code>LINE_START</code>, and <code>LINE_END</code>. |
| 57 | * In a container whose <code>ComponentOrientation</code> is set to |
| 58 | * <code>ComponentOrientation.LEFT_TO_RIGHT</code>, these constants map to |
| 59 | * <code>NORTH</code>, <code>SOUTH</code>, <code>WEST</code>, and |
| 60 | * <code>EAST</code>, respectively. |
| 61 | * <p> |
| 62 | * For compatibility with previous releases, <code>BorderLayout</code> |
| 63 | * also includes the relative positioning constants <code>BEFORE_FIRST_LINE</code>, |
| 64 | * <code>AFTER_LAST_LINE</code>, <code>BEFORE_LINE_BEGINS</code> and |
| 65 | * <code>AFTER_LINE_ENDS</code>. These are equivalent to |
| 66 | * <code>PAGE_START</code>, <code>PAGE_END</code>, <code>LINE_START</code> |
| 67 | * and <code>LINE_END</code> respectively. For |
| 68 | * consistency with the relative positioning constants used by other |
| 69 | * components, the latter constants are preferred. |
| 70 | * <p> |
| 71 | * Mixing both absolute and relative positioning constants can lead to |
| 72 | * unpredicable results. If |
| 73 | * you use both types, the relative constants will take precedence. |
| 74 | * For example, if you add components using both the <code>NORTH</code> |
| 75 | * and <code>PAGE_START</code> constants in a container whose |
| 76 | * orientation is <code>LEFT_TO_RIGHT</code>, only the |
| 77 | * <code>PAGE_START</code> will be layed out. |
| 78 | * <p> |
| 79 | * NOTE: Currently (in the Java 2 platform v1.2), |
| 80 | * <code>BorderLayout</code> does not support vertical |
| 81 | * orientations. The <code>isVertical</code> setting on the container's |
| 82 | * <code>ComponentOrientation</code> is not respected. |
| 83 | * <p> |
| 84 | * The components are laid out according to their |
| 85 | * preferred sizes and the constraints of the container's size. |
| 86 | * The <code>NORTH</code> and <code>SOUTH</code> components may |
| 87 | * be stretched horizontally; the <code>EAST</code> and |
| 88 | * <code>WEST</code> components may be stretched vertically; |
| 89 | * the <code>CENTER</code> component may stretch both horizontally |
| 90 | * and vertically to fill any space left over. |
| 91 | * <p> |
| 92 | * Here is an example of five buttons in an applet laid out using |
| 93 | * the <code>BorderLayout</code> layout manager: |
| 94 | * <p> |
| 95 | * <img src="doc-files/BorderLayout-1.gif" |
| 96 | * alt="Diagram of an applet demonstrating BorderLayout. |
| 97 | * Each section of the BorderLayout contains a Button corresponding to its position in the layout, one of: |
| 98 | * North, West, Center, East, or South." |
| 99 | * ALIGN=center HSPACE=10 VSPACE=7> |
| 100 | * <p> |
| 101 | * The code for this applet is as follows: |
| 102 | * <p> |
| 103 | * <hr><blockquote><pre> |
| 104 | * import java.awt.*; |
| 105 | * import java.applet.Applet; |
| 106 | * |
| 107 | * public class buttonDir extends Applet { |
| 108 | * public void init() { |
| 109 | * setLayout(new BorderLayout()); |
| 110 | * add(new Button("North"), BorderLayout.NORTH); |
| 111 | * add(new Button("South"), BorderLayout.SOUTH); |
| 112 | * add(new Button("East"), BorderLayout.EAST); |
| 113 | * add(new Button("West"), BorderLayout.WEST); |
| 114 | * add(new Button("Center"), BorderLayout.CENTER); |
| 115 | * } |
| 116 | * } |
| 117 | * </pre></blockquote><hr> |
| 118 | * <p> |
| 119 | * @author Arthur van Hoff |
| 120 | * @see java.awt.Container#add(String, Component) |
| 121 | * @see java.awt.ComponentOrientation |
| 122 | * @since JDK1.0 |
| 123 | */ |
| 124 | public class BorderLayout implements LayoutManager2, |
| 125 | java.io.Serializable { |
| 126 | /** |
| 127 | * Constructs a border layout with the horizontal gaps |
| 128 | * between components. |
| 129 | * The horizontal gap is specified by <code>hgap</code>. |
| 130 | * |
| 131 | * @see #getHgap() |
| 132 | * @see #setHgap(int) |
| 133 | * |
| 134 | * @serial |
| 135 | */ |
| 136 | int hgap; |
| 137 | |
| 138 | /** |
| 139 | * Constructs a border layout with the vertical gaps |
| 140 | * between components. |
| 141 | * The vertical gap is specified by <code>vgap</code>. |
| 142 | * |
| 143 | * @see #getVgap() |
| 144 | * @see #setVgap(int) |
| 145 | * @serial |
| 146 | */ |
| 147 | int vgap; |
| 148 | |
| 149 | /** |
| 150 | * Constant to specify components location to be the |
| 151 | * north portion of the border layout. |
| 152 | * @serial |
| 153 | * @see #getChild(String, boolean) |
| 154 | * @see #addLayoutComponent |
| 155 | * @see #getLayoutAlignmentX |
| 156 | * @see #getLayoutAlignmentY |
| 157 | * @see #removeLayoutComponent |
| 158 | */ |
| 159 | Component north; |
| 160 | /** |
| 161 | * Constant to specify components location to be the |
| 162 | * west portion of the border layout. |
| 163 | * @serial |
| 164 | * @see #getChild(String, boolean) |
| 165 | * @see #addLayoutComponent |
| 166 | * @see #getLayoutAlignmentX |
| 167 | * @see #getLayoutAlignmentY |
| 168 | * @see #removeLayoutComponent |
| 169 | */ |
| 170 | Component west; |
| 171 | /** |
| 172 | * Constant to specify components location to be the |
| 173 | * east portion of the border layout. |
| 174 | * @serial |
| 175 | * @see #getChild(String, boolean) |
| 176 | * @see #addLayoutComponent |
| 177 | * @see #getLayoutAlignmentX |
| 178 | * @see #getLayoutAlignmentY |
| 179 | * @see #removeLayoutComponent |
| 180 | */ |
| 181 | Component east; |
| 182 | /** |
| 183 | * Constant to specify components location to be the |
| 184 | * south portion of the border layout. |
| 185 | * @serial |
| 186 | * @see #getChild(String, boolean) |
| 187 | * @see #addLayoutComponent |
| 188 | * @see #getLayoutAlignmentX |
| 189 | * @see #getLayoutAlignmentY |
| 190 | * @see #removeLayoutComponent |
| 191 | */ |
| 192 | Component south; |
| 193 | /** |
| 194 | * Constant to specify components location to be the |
| 195 | * center portion of the border layout. |
| 196 | * @serial |
| 197 | * @see #getChild(String, boolean) |
| 198 | * @see #addLayoutComponent |
| 199 | * @see #getLayoutAlignmentX |
| 200 | * @see #getLayoutAlignmentY |
| 201 | * @see #removeLayoutComponent |
| 202 | */ |
| 203 | Component center; |
| 204 | |
| 205 | /** |
| 206 | * |
| 207 | * A relative positioning constant, that can be used instead of |
| 208 | * north, south, east, west or center. |
| 209 | * mixing the two types of constants can lead to unpredicable results. If |
| 210 | * you use both types, the relative constants will take precedence. |
| 211 | * For example, if you add components using both the <code>NORTH</code> |
| 212 | * and <code>BEFORE_FIRST_LINE</code> constants in a container whose |
| 213 | * orientation is <code>LEFT_TO_RIGHT</code>, only the |
| 214 | * <code>BEFORE_FIRST_LINE</code> will be layed out. |
| 215 | * This will be the same for lastLine, firstItem, lastItem. |
| 216 | * @serial |
| 217 | */ |
| 218 | Component firstLine; |
| 219 | /** |
| 220 | * A relative positioning constant, that can be used instead of |
| 221 | * north, south, east, west or center. |
| 222 | * Please read Description for firstLine. |
| 223 | * @serial |
| 224 | */ |
| 225 | Component lastLine; |
| 226 | /** |
| 227 | * A relative positioning constant, that can be used instead of |
| 228 | * north, south, east, west or center. |
| 229 | * Please read Description for firstLine. |
| 230 | * @serial |
| 231 | */ |
| 232 | Component firstItem; |
| 233 | /** |
| 234 | * A relative positioning constant, that can be used instead of |
| 235 | * north, south, east, west or center. |
| 236 | * Please read Description for firstLine. |
| 237 | * @serial |
| 238 | */ |
| 239 | Component lastItem; |
| 240 | |
| 241 | /** |
| 242 | * The north layout constraint (top of container). |
| 243 | */ |
| 244 | public static final String NORTH = "North"; |
| 245 | |
| 246 | /** |
| 247 | * The south layout constraint (bottom of container). |
| 248 | */ |
| 249 | public static final String SOUTH = "South"; |
| 250 | |
| 251 | /** |
| 252 | * The east layout constraint (right side of container). |
| 253 | */ |
| 254 | public static final String EAST = "East"; |
| 255 | |
| 256 | /** |
| 257 | * The west layout constraint (left side of container). |
| 258 | */ |
| 259 | public static final String WEST = "West"; |
| 260 | |
| 261 | /** |
| 262 | * The center layout constraint (middle of container). |
| 263 | */ |
| 264 | public static final String CENTER = "Center"; |
| 265 | |
| 266 | /** |
| 267 | * Synonym for PAGE_START. Exists for compatibility with previous |
| 268 | * versions. PAGE_START is preferred. |
| 269 | * |
| 270 | * @see #PAGE_START |
| 271 | * @since 1.2 |
| 272 | */ |
| 273 | public static final String BEFORE_FIRST_LINE = "First"; |
| 274 | |
| 275 | /** |
| 276 | * Synonym for PAGE_END. Exists for compatibility with previous |
| 277 | * versions. PAGE_END is preferred. |
| 278 | * |
| 279 | * @see #PAGE_END |
| 280 | * @since 1.2 |
| 281 | */ |
| 282 | public static final String AFTER_LAST_LINE = "Last"; |
| 283 | |
| 284 | /** |
| 285 | * Synonym for LINE_START. Exists for compatibility with previous |
| 286 | * versions. LINE_START is preferred. |
| 287 | * |
| 288 | * @see #LINE_START |
| 289 | * @since 1.2 |
| 290 | */ |
| 291 | public static final String BEFORE_LINE_BEGINS = "Before"; |
| 292 | |
| 293 | /** |
| 294 | * Synonym for LINE_END. Exists for compatibility with previous |
| 295 | * versions. LINE_END is preferred. |
| 296 | * |
| 297 | * @see #LINE_END |
| 298 | * @since 1.2 |
| 299 | */ |
| 300 | public static final String AFTER_LINE_ENDS = "After"; |
| 301 | |
| 302 | /** |
| 303 | * The component comes before the first line of the layout's content. |
| 304 | * For Western, left-to-right and top-to-bottom orientations, this is |
| 305 | * equivalent to NORTH. |
| 306 | * |
| 307 | * @see java.awt.Component#getComponentOrientation |
| 308 | * @since 1.4 |
| 309 | */ |
| 310 | public static final String PAGE_START = BEFORE_FIRST_LINE; |
| 311 | |
| 312 | /** |
| 313 | * The component comes after the last line of the layout's content. |
| 314 | * For Western, left-to-right and top-to-bottom orientations, this is |
| 315 | * equivalent to SOUTH. |
| 316 | * |
| 317 | * @see java.awt.Component#getComponentOrientation |
| 318 | * @since 1.4 |
| 319 | */ |
| 320 | public static final String PAGE_END = AFTER_LAST_LINE; |
| 321 | |
| 322 | /** |
| 323 | * The component goes at the beginning of the line direction for the |
| 324 | * layout. For Western, left-to-right and top-to-bottom orientations, |
| 325 | * this is equivalent to WEST. |
| 326 | * |
| 327 | * @see java.awt.Component#getComponentOrientation |
| 328 | * @since 1.4 |
| 329 | */ |
| 330 | public static final String LINE_START = BEFORE_LINE_BEGINS; |
| 331 | |
| 332 | /** |
| 333 | * The component goes at the end of the line direction for the |
| 334 | * layout. For Western, left-to-right and top-to-bottom orientations, |
| 335 | * this is equivalent to EAST. |
| 336 | * |
| 337 | * @see java.awt.Component#getComponentOrientation |
| 338 | * @since 1.4 |
| 339 | */ |
| 340 | public static final String LINE_END = AFTER_LINE_ENDS; |
| 341 | |
| 342 | /* |
| 343 | * JDK 1.1 serialVersionUID |
| 344 | */ |
| 345 | private static final long serialVersionUID = -8658291919501921765L; |
| 346 | |
| 347 | /** |
| 348 | * Constructs a new border layout with |
| 349 | * no gaps between components. |
| 350 | */ |
| 351 | public BorderLayout() { |
| 352 | this(0, 0); |
| 353 | } |
| 354 | |
| 355 | /** |
| 356 | * Constructs a border layout with the specified gaps |
| 357 | * between components. |
| 358 | * The horizontal gap is specified by <code>hgap</code> |
| 359 | * and the vertical gap is specified by <code>vgap</code>. |
| 360 | * @param hgap the horizontal gap. |
| 361 | * @param vgap the vertical gap. |
| 362 | */ |
| 363 | public BorderLayout(int hgap, int vgap) { |
| 364 | this.hgap = hgap; |
| 365 | this.vgap = vgap; |
| 366 | } |
| 367 | |
| 368 | /** |
| 369 | * Returns the horizontal gap between components. |
| 370 | * @since JDK1.1 |
| 371 | */ |
| 372 | public int getHgap() { |
| 373 | return hgap; |
| 374 | } |
| 375 | |
| 376 | /** |
| 377 | * Sets the horizontal gap between components. |
| 378 | * @param hgap the horizontal gap between components |
| 379 | * @since JDK1.1 |
| 380 | */ |
| 381 | public void setHgap(int hgap) { |
| 382 | this.hgap = hgap; |
| 383 | } |
| 384 | |
| 385 | /** |
| 386 | * Returns the vertical gap between components. |
| 387 | * @since JDK1.1 |
| 388 | */ |
| 389 | public int getVgap() { |
| 390 | return vgap; |
| 391 | } |
| 392 | |
| 393 | /** |
| 394 | * Sets the vertical gap between components. |
| 395 | * @param vgap the vertical gap between components |
| 396 | * @since JDK1.1 |
| 397 | */ |
| 398 | public void setVgap(int vgap) { |
| 399 | this.vgap = vgap; |
| 400 | } |
| 401 | |
| 402 | /** |
| 403 | * Adds the specified component to the layout, using the specified |
| 404 | * constraint object. For border layouts, the constraint must be |
| 405 | * one of the following constants: <code>NORTH</code>, |
| 406 | * <code>SOUTH</code>, <code>EAST</code>, |
| 407 | * <code>WEST</code>, or <code>CENTER</code>. |
| 408 | * <p> |
| 409 | * Most applications do not call this method directly. This method |
| 410 | * is called when a component is added to a container using the |
| 411 | * <code>Container.add</code> method with the same argument types. |
| 412 | * @param comp the component to be added. |
| 413 | * @param constraints an object that specifies how and where |
| 414 | * the component is added to the layout. |
| 415 | * @see java.awt.Container#add(java.awt.Component, java.lang.Object) |
| 416 | * @exception IllegalArgumentException if the constraint object is not |
| 417 | * a string, or if it not one of the five specified |
| 418 | * constants. |
| 419 | * @since JDK1.1 |
| 420 | */ |
| 421 | public void addLayoutComponent(Component comp, Object constraints) { |
| 422 | synchronized (comp.getTreeLock()) { |
| 423 | if ((constraints == null) || (constraints instanceof String)) { |
| 424 | addLayoutComponent((String)constraints, comp); |
| 425 | } else { |
| 426 | throw new IllegalArgumentException("cannot add to layout: constraint must be a string (or null)"); |
| 427 | } |
| 428 | } |
| 429 | } |
| 430 | |
| 431 | /** |
| 432 | * @deprecated replaced by <code>addLayoutComponent(Component, Object)</code>. |
| 433 | */ |
| 434 | @Deprecated |
| 435 | public void addLayoutComponent(String name, Component comp) { |
| 436 | synchronized (comp.getTreeLock()) { |
| 437 | /* Special case: treat null the same as "Center". */ |
| 438 | if (name == null) { |
| 439 | name = "Center"; |
| 440 | } |
| 441 | |
| 442 | /* Assign the component to one of the known regions of the layout. |
| 443 | */ |
| 444 | if ("Center".equals(name)) { |
| 445 | center = comp; |
| 446 | } else if ("North".equals(name)) { |
| 447 | north = comp; |
| 448 | } else if ("South".equals(name)) { |
| 449 | south = comp; |
| 450 | } else if ("East".equals(name)) { |
| 451 | east = comp; |
| 452 | } else if ("West".equals(name)) { |
| 453 | west = comp; |
| 454 | } else if (BEFORE_FIRST_LINE.equals(name)) { |
| 455 | firstLine = comp; |
| 456 | } else if (AFTER_LAST_LINE.equals(name)) { |
| 457 | lastLine = comp; |
| 458 | } else if (BEFORE_LINE_BEGINS.equals(name)) { |
| 459 | firstItem = comp; |
| 460 | } else if (AFTER_LINE_ENDS.equals(name)) { |
| 461 | lastItem = comp; |
| 462 | } else { |
| 463 | throw new IllegalArgumentException("cannot add to layout: unknown constraint: " + name); |
| 464 | } |
| 465 | } |
| 466 | } |
| 467 | |
| 468 | /** |
| 469 | * Removes the specified component from this border layout. This |
| 470 | * method is called when a container calls its <code>remove</code> or |
| 471 | * <code>removeAll</code> methods. Most applications do not call this |
| 472 | * method directly. |
| 473 | * @param comp the component to be removed. |
| 474 | * @see java.awt.Container#remove(java.awt.Component) |
| 475 | * @see java.awt.Container#removeAll() |
| 476 | */ |
| 477 | public void removeLayoutComponent(Component comp) { |
| 478 | synchronized (comp.getTreeLock()) { |
| 479 | if (comp == center) { |
| 480 | center = null; |
| 481 | } else if (comp == north) { |
| 482 | north = null; |
| 483 | } else if (comp == south) { |
| 484 | south = null; |
| 485 | } else if (comp == east) { |
| 486 | east = null; |
| 487 | } else if (comp == west) { |
| 488 | west = null; |
| 489 | } |
| 490 | if (comp == firstLine) { |
| 491 | firstLine = null; |
| 492 | } else if (comp == lastLine) { |
| 493 | lastLine = null; |
| 494 | } else if (comp == firstItem) { |
| 495 | firstItem = null; |
| 496 | } else if (comp == lastItem) { |
| 497 | lastItem = null; |
| 498 | } |
| 499 | } |
| 500 | } |
| 501 | |
| 502 | /** |
| 503 | * Gets the component that was added using the given constraint |
| 504 | * |
| 505 | * @param constraints the desired constraint, one of <code>CENTER</code>, |
| 506 | * <code>NORTH</code>, <code>SOUTH</code>, |
| 507 | * <code>WEST</code>, <code>EAST</code>, |
| 508 | * <code>PAGE_START</code>, <code>PAGE_END</code>, |
| 509 | * <code>LINE_START</code>, <code>LINE_END</code> |
| 510 | * @return the component at the given location, or <code>null</code> if |
| 511 | * the location is empty |
| 512 | * @exception IllegalArgumentException if the constraint object is |
| 513 | * not one of the nine specified constants |
| 514 | * @see #addLayoutComponent(java.awt.Component, java.lang.Object) |
| 515 | * @since 1.5 |
| 516 | */ |
| 517 | public Component getLayoutComponent(Object constraints) { |
| 518 | if (CENTER.equals(constraints)) { |
| 519 | return center; |
| 520 | } else if (NORTH.equals(constraints)) { |
| 521 | return north; |
| 522 | } else if (SOUTH.equals(constraints)) { |
| 523 | return south; |
| 524 | } else if (WEST.equals(constraints)) { |
| 525 | return west; |
| 526 | } else if (EAST.equals(constraints)) { |
| 527 | return east; |
| 528 | } else if (PAGE_START.equals(constraints)) { |
| 529 | return firstLine; |
| 530 | } else if (PAGE_END.equals(constraints)) { |
| 531 | return lastLine; |
| 532 | } else if (LINE_START.equals(constraints)) { |
| 533 | return firstItem; |
| 534 | } else if (LINE_END.equals(constraints)) { |
| 535 | return lastItem; |
| 536 | } else { |
| 537 | throw new IllegalArgumentException("cannot get component: unknown constraint: " + constraints); |
| 538 | } |
| 539 | } |
| 540 | |
| 541 | |
| 542 | /** |
| 543 | * Returns the component that corresponds to the given constraint location |
| 544 | * based on the target <code>Container</code>'s component orientation. |
| 545 | * Components added with the relative constraints <code>PAGE_START</code>, |
| 546 | * <code>PAGE_END</code>, <code>LINE_START</code>, and <code>LINE_END</code> |
| 547 | * take precedence over components added with the explicit constraints |
| 548 | * <code>NORTH</code>, <code>SOUTH</code>, <code>WEST</code>, and <code>EAST</code>. |
| 549 | * The <code>Container</code>'s component orientation is used to determine the location of components |
| 550 | * added with <code>LINE_START</code> and <code>LINE_END</code>. |
| 551 | * |
| 552 | * @param constraints the desired absolute position, one of <code>CENTER</code>, |
| 553 | * <code>NORTH</code>, <code>SOUTH</code>, |
| 554 | * <code>EAST</code>, <code>WEST</code> |
| 555 | * @param target the {@code Container} used to obtain |
| 556 | * the constraint location based on the target |
| 557 | * {@code Container}'s component orientation. |
| 558 | * @return the component at the given location, or <code>null</code> if |
| 559 | * the location is empty |
| 560 | * @exception IllegalArgumentException if the constraint object is |
| 561 | * not one of the five specified constants |
| 562 | * @exception NullPointerException if the target parameter is null |
| 563 | * @see #addLayoutComponent(java.awt.Component, java.lang.Object) |
| 564 | * @since 1.5 |
| 565 | */ |
| 566 | public Component getLayoutComponent(Container target, Object constraints) { |
| 567 | boolean ltr = target.getComponentOrientation().isLeftToRight(); |
| 568 | Component result = null; |
| 569 | |
| 570 | if (NORTH.equals(constraints)) { |
| 571 | result = (firstLine != null) ? firstLine : north; |
| 572 | } else if (SOUTH.equals(constraints)) { |
| 573 | result = (lastLine != null) ? lastLine : south; |
| 574 | } else if (WEST.equals(constraints)) { |
| 575 | result = ltr ? firstItem : lastItem; |
| 576 | if (result == null) { |
| 577 | result = west; |
| 578 | } |
| 579 | } else if (EAST.equals(constraints)) { |
| 580 | result = ltr ? lastItem : firstItem; |
| 581 | if (result == null) { |
| 582 | result = east; |
| 583 | } |
| 584 | } else if (CENTER.equals(constraints)) { |
| 585 | result = center; |
| 586 | } else { |
| 587 | throw new IllegalArgumentException("cannot get component: invalid constraint: " + constraints); |
| 588 | } |
| 589 | |
| 590 | return result; |
| 591 | } |
| 592 | |
| 593 | |
| 594 | /** |
| 595 | * Gets the constraints for the specified component |
| 596 | * |
| 597 | * @param comp the component to be queried |
| 598 | * @return the constraint for the specified component, |
| 599 | * or null if component is null or is not present |
| 600 | * in this layout |
| 601 | * @see #addLayoutComponent(java.awt.Component, java.lang.Object) |
| 602 | * @since 1.5 |
| 603 | */ |
| 604 | public Object getConstraints(Component comp) { |
| 605 | //fix for 6242148 : API method java.awt.BorderLayout.getConstraints(null) should return null |
| 606 | if (comp == null){ |
| 607 | return null; |
| 608 | } |
| 609 | if (comp == center) { |
| 610 | return CENTER; |
| 611 | } else if (comp == north) { |
| 612 | return NORTH; |
| 613 | } else if (comp == south) { |
| 614 | return SOUTH; |
| 615 | } else if (comp == west) { |
| 616 | return WEST; |
| 617 | } else if (comp == east) { |
| 618 | return EAST; |
| 619 | } else if (comp == firstLine) { |
| 620 | return PAGE_START; |
| 621 | } else if (comp == lastLine) { |
| 622 | return PAGE_END; |
| 623 | } else if (comp == firstItem) { |
| 624 | return LINE_START; |
| 625 | } else if (comp == lastItem) { |
| 626 | return LINE_END; |
| 627 | } |
| 628 | return null; |
| 629 | } |
| 630 | |
| 631 | /** |
| 632 | * Determines the minimum size of the <code>target</code> container |
| 633 | * using this layout manager. |
| 634 | * <p> |
| 635 | * This method is called when a container calls its |
| 636 | * <code>getMinimumSize</code> method. Most applications do not call |
| 637 | * this method directly. |
| 638 | * @param target the container in which to do the layout. |
| 639 | * @return the minimum dimensions needed to lay out the subcomponents |
| 640 | * of the specified container. |
| 641 | * @see java.awt.Container |
| 642 | * @see java.awt.BorderLayout#preferredLayoutSize |
| 643 | * @see java.awt.Container#getMinimumSize() |
| 644 | */ |
| 645 | public Dimension minimumLayoutSize(Container target) { |
| 646 | synchronized (target.getTreeLock()) { |
| 647 | Dimension dim = new Dimension(0, 0); |
| 648 | |
| 649 | boolean ltr = target.getComponentOrientation().isLeftToRight(); |
| 650 | Component c = null; |
| 651 | |
| 652 | if ((c=getChild(EAST,ltr)) != null) { |
| 653 | Dimension d = c.getMinimumSize(); |
| 654 | dim.width += d.width + hgap; |
| 655 | dim.height = Math.max(d.height, dim.height); |
| 656 | } |
| 657 | if ((c=getChild(WEST,ltr)) != null) { |
| 658 | Dimension d = c.getMinimumSize(); |
| 659 | dim.width += d.width + hgap; |
| 660 | dim.height = Math.max(d.height, dim.height); |
| 661 | } |
| 662 | if ((c=getChild(CENTER,ltr)) != null) { |
| 663 | Dimension d = c.getMinimumSize(); |
| 664 | dim.width += d.width; |
| 665 | dim.height = Math.max(d.height, dim.height); |
| 666 | } |
| 667 | if ((c=getChild(NORTH,ltr)) != null) { |
| 668 | Dimension d = c.getMinimumSize(); |
| 669 | dim.width = Math.max(d.width, dim.width); |
| 670 | dim.height += d.height + vgap; |
| 671 | } |
| 672 | if ((c=getChild(SOUTH,ltr)) != null) { |
| 673 | Dimension d = c.getMinimumSize(); |
| 674 | dim.width = Math.max(d.width, dim.width); |
| 675 | dim.height += d.height + vgap; |
| 676 | } |
| 677 | |
| 678 | Insets insets = target.getInsets(); |
| 679 | dim.width += insets.left + insets.right; |
| 680 | dim.height += insets.top + insets.bottom; |
| 681 | |
| 682 | return dim; |
| 683 | } |
| 684 | } |
| 685 | |
| 686 | /** |
| 687 | * Determines the preferred size of the <code>target</code> |
| 688 | * container using this layout manager, based on the components |
| 689 | * in the container. |
| 690 | * <p> |
| 691 | * Most applications do not call this method directly. This method |
| 692 | * is called when a container calls its <code>getPreferredSize</code> |
| 693 | * method. |
| 694 | * @param target the container in which to do the layout. |
| 695 | * @return the preferred dimensions to lay out the subcomponents |
| 696 | * of the specified container. |
| 697 | * @see java.awt.Container |
| 698 | * @see java.awt.BorderLayout#minimumLayoutSize |
| 699 | * @see java.awt.Container#getPreferredSize() |
| 700 | */ |
| 701 | public Dimension preferredLayoutSize(Container target) { |
| 702 | synchronized (target.getTreeLock()) { |
| 703 | Dimension dim = new Dimension(0, 0); |
| 704 | |
| 705 | boolean ltr = target.getComponentOrientation().isLeftToRight(); |
| 706 | Component c = null; |
| 707 | |
| 708 | if ((c=getChild(EAST,ltr)) != null) { |
| 709 | Dimension d = c.getPreferredSize(); |
| 710 | dim.width += d.width + hgap; |
| 711 | dim.height = Math.max(d.height, dim.height); |
| 712 | } |
| 713 | if ((c=getChild(WEST,ltr)) != null) { |
| 714 | Dimension d = c.getPreferredSize(); |
| 715 | dim.width += d.width + hgap; |
| 716 | dim.height = Math.max(d.height, dim.height); |
| 717 | } |
| 718 | if ((c=getChild(CENTER,ltr)) != null) { |
| 719 | Dimension d = c.getPreferredSize(); |
| 720 | dim.width += d.width; |
| 721 | dim.height = Math.max(d.height, dim.height); |
| 722 | } |
| 723 | if ((c=getChild(NORTH,ltr)) != null) { |
| 724 | Dimension d = c.getPreferredSize(); |
| 725 | dim.width = Math.max(d.width, dim.width); |
| 726 | dim.height += d.height + vgap; |
| 727 | } |
| 728 | if ((c=getChild(SOUTH,ltr)) != null) { |
| 729 | Dimension d = c.getPreferredSize(); |
| 730 | dim.width = Math.max(d.width, dim.width); |
| 731 | dim.height += d.height + vgap; |
| 732 | } |
| 733 | |
| 734 | Insets insets = target.getInsets(); |
| 735 | dim.width += insets.left + insets.right; |
| 736 | dim.height += insets.top + insets.bottom; |
| 737 | |
| 738 | return dim; |
| 739 | } |
| 740 | } |
| 741 | |
| 742 | /** |
| 743 | * Returns the maximum dimensions for this layout given the components |
| 744 | * in the specified target container. |
| 745 | * @param target the component which needs to be laid out |
| 746 | * @see Container |
| 747 | * @see #minimumLayoutSize |
| 748 | * @see #preferredLayoutSize |
| 749 | */ |
| 750 | public Dimension maximumLayoutSize(Container target) { |
| 751 | return new Dimension(Integer.MAX_VALUE, Integer.MAX_VALUE); |
| 752 | } |
| 753 | |
| 754 | /** |
| 755 | * Returns the alignment along the x axis. This specifies how |
| 756 | * the component would like to be aligned relative to other |
| 757 | * components. The value should be a number between 0 and 1 |
| 758 | * where 0 represents alignment along the origin, 1 is aligned |
| 759 | * the furthest away from the origin, 0.5 is centered, etc. |
| 760 | */ |
| 761 | public float getLayoutAlignmentX(Container parent) { |
| 762 | return 0.5f; |
| 763 | } |
| 764 | |
| 765 | /** |
| 766 | * Returns the alignment along the y axis. This specifies how |
| 767 | * the component would like to be aligned relative to other |
| 768 | * components. The value should be a number between 0 and 1 |
| 769 | * where 0 represents alignment along the origin, 1 is aligned |
| 770 | * the furthest away from the origin, 0.5 is centered, etc. |
| 771 | */ |
| 772 | public float getLayoutAlignmentY(Container parent) { |
| 773 | return 0.5f; |
| 774 | } |
| 775 | |
| 776 | /** |
| 777 | * Invalidates the layout, indicating that if the layout manager |
| 778 | * has cached information it should be discarded. |
| 779 | */ |
| 780 | public void invalidateLayout(Container target) { |
| 781 | } |
| 782 | |
| 783 | /** |
| 784 | * Lays out the container argument using this border layout. |
| 785 | * <p> |
| 786 | * This method actually reshapes the components in the specified |
| 787 | * container in order to satisfy the constraints of this |
| 788 | * <code>BorderLayout</code> object. The <code>NORTH</code> |
| 789 | * and <code>SOUTH</code> components, if any, are placed at |
| 790 | * the top and bottom of the container, respectively. The |
| 791 | * <code>WEST</code> and <code>EAST</code> components are |
| 792 | * then placed on the left and right, respectively. Finally, |
| 793 | * the <code>CENTER</code> object is placed in any remaining |
| 794 | * space in the middle. |
| 795 | * <p> |
| 796 | * Most applications do not call this method directly. This method |
| 797 | * is called when a container calls its <code>doLayout</code> method. |
| 798 | * @param target the container in which to do the layout. |
| 799 | * @see java.awt.Container |
| 800 | * @see java.awt.Container#doLayout() |
| 801 | */ |
| 802 | public void layoutContainer(Container target) { |
| 803 | synchronized (target.getTreeLock()) { |
| 804 | Insets insets = target.getInsets(); |
| 805 | int top = insets.top; |
| 806 | int bottom = target.height - insets.bottom; |
| 807 | int left = insets.left; |
| 808 | int right = target.width - insets.right; |
| 809 | |
| 810 | boolean ltr = target.getComponentOrientation().isLeftToRight(); |
| 811 | Component c = null; |
| 812 | |
| 813 | if ((c=getChild(NORTH,ltr)) != null) { |
| 814 | c.setSize(right - left, c.height); |
| 815 | Dimension d = c.getPreferredSize(); |
| 816 | c.setBounds(left, top, right - left, d.height); |
| 817 | top += d.height + vgap; |
| 818 | } |
| 819 | if ((c=getChild(SOUTH,ltr)) != null) { |
| 820 | c.setSize(right - left, c.height); |
| 821 | Dimension d = c.getPreferredSize(); |
| 822 | c.setBounds(left, bottom - d.height, right - left, d.height); |
| 823 | bottom -= d.height + vgap; |
| 824 | } |
| 825 | if ((c=getChild(EAST,ltr)) != null) { |
| 826 | c.setSize(c.width, bottom - top); |
| 827 | Dimension d = c.getPreferredSize(); |
| 828 | c.setBounds(right - d.width, top, d.width, bottom - top); |
| 829 | right -= d.width + hgap; |
| 830 | } |
| 831 | if ((c=getChild(WEST,ltr)) != null) { |
| 832 | c.setSize(c.width, bottom - top); |
| 833 | Dimension d = c.getPreferredSize(); |
| 834 | c.setBounds(left, top, d.width, bottom - top); |
| 835 | left += d.width + hgap; |
| 836 | } |
| 837 | if ((c=getChild(CENTER,ltr)) != null) { |
| 838 | c.setBounds(left, top, right - left, bottom - top); |
| 839 | } |
| 840 | } |
| 841 | } |
| 842 | |
| 843 | /** |
| 844 | * Get the component that corresponds to the given constraint location |
| 845 | * |
| 846 | * @param key The desired absolute position, |
| 847 | * either NORTH, SOUTH, EAST, or WEST. |
| 848 | * @param ltr Is the component line direction left-to-right? |
| 849 | */ |
| 850 | private Component getChild(String key, boolean ltr) { |
| 851 | Component result = null; |
| 852 | |
| 853 | if (key == NORTH) { |
| 854 | result = (firstLine != null) ? firstLine : north; |
| 855 | } |
| 856 | else if (key == SOUTH) { |
| 857 | result = (lastLine != null) ? lastLine : south; |
| 858 | } |
| 859 | else if (key == WEST) { |
| 860 | result = ltr ? firstItem : lastItem; |
| 861 | if (result == null) { |
| 862 | result = west; |
| 863 | } |
| 864 | } |
| 865 | else if (key == EAST) { |
| 866 | result = ltr ? lastItem : firstItem; |
| 867 | if (result == null) { |
| 868 | result = east; |
| 869 | } |
| 870 | } |
| 871 | else if (key == CENTER) { |
| 872 | result = center; |
| 873 | } |
| 874 | if (result != null && !result.visible) { |
| 875 | result = null; |
| 876 | } |
| 877 | return result; |
| 878 | } |
| 879 | |
| 880 | /** |
| 881 | * Returns a string representation of the state of this border layout. |
| 882 | * @return a string representation of this border layout. |
| 883 | */ |
| 884 | public String toString() { |
| 885 | return getClass().getName() + "[hgap=" + hgap + ",vgap=" + vgap + "]"; |
| 886 | } |
| 887 | } |