1 /* 2 * Copyright (c) 1997, 2017, 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 26 27 package javax.swing; 28 29 import java.awt.*; 30 import java.beans.ConstructorProperties; 31 import java.io.Serializable; 32 import java.io.PrintStream; 33 34 /** 35 * A layout manager that allows multiple components to be laid out either 36 * vertically or horizontally. The components will not wrap so, for 37 * example, a vertical arrangement of components will stay vertically 38 * arranged when the frame is resized. 39 * <TABLE STYLE="FLOAT:RIGHT" BORDER="0" SUMMARY="layout"> 40 * <TR> 41 * <TD style="text-align:center"> 42 * <P STYLE="TEXT-ALIGN:CENTER"><IMG SRC="doc-files/BoxLayout-1.gif" 43 * alt="The following text describes this graphic." 44 * WIDTH="191" HEIGHT="201" STYLE="FLOAT:BOTTOM; BORDER:0"> 45 * </TD> 46 * </TR> 47 * </TABLE> 48 * <p> 49 * Nesting multiple panels with different combinations of horizontal and 50 * vertical gives an effect similar to GridBagLayout, without the 51 * complexity. The diagram shows two panels arranged horizontally, each 52 * of which contains 3 components arranged vertically. 53 * 54 * <p> The BoxLayout manager is constructed with an axis parameter that 55 * specifies the type of layout that will be done. There are four choices: 56 * 57 * <blockquote><b>{@code X_AXIS}</b> - Components are laid out horizontally 58 * from left to right.</blockquote> 59 * 60 * <blockquote><b>{@code Y_AXIS}</b> - Components are laid out vertically 61 * from top to bottom.</blockquote> 62 * 63 * <blockquote><b>{@code LINE_AXIS}</b> - Components are laid out the way 64 * words are laid out in a line, based on the container's 65 * {@code ComponentOrientation} property. If the container's 66 * {@code ComponentOrientation} is horizontal then components are laid out 67 * horizontally, otherwise they are laid out vertically. For horizontal 68 * orientations, if the container's {@code ComponentOrientation} is left to 69 * right then components are laid out left to right, otherwise they are laid 70 * out right to left. For vertical orientations components are always laid out 71 * from top to bottom.</blockquote> 72 * 73 * <blockquote><b>{@code PAGE_AXIS}</b> - Components are laid out the way 74 * text lines are laid out on a page, based on the container's 75 * {@code ComponentOrientation} property. If the container's 76 * {@code ComponentOrientation} is horizontal then components are laid out 77 * vertically, otherwise they are laid out horizontally. For horizontal 78 * orientations, if the container's {@code ComponentOrientation} is left to 79 * right then components are laid out left to right, otherwise they are laid 80 * out right to left. For vertical orientations components are always 81 * laid out from top to bottom.</blockquote> 82 * <p> 83 * For all directions, components are arranged in the same order as they were 84 * added to the container. 85 * <p> 86 * BoxLayout attempts to arrange components 87 * at their preferred widths (for horizontal layout) 88 * or heights (for vertical layout). 89 * For a horizontal layout, 90 * if not all the components are the same height, 91 * BoxLayout attempts to make all the components 92 * as high as the highest component. 93 * If that's not possible for a particular component, 94 * then BoxLayout aligns that component vertically, 95 * according to the component's Y alignment. 96 * By default, a component has a Y alignment of 0.5, 97 * which means that the vertical center of the component 98 * should have the same Y coordinate as 99 * the vertical centers of other components with 0.5 Y alignment. 100 * <p> 101 * Similarly, for a vertical layout, 102 * BoxLayout attempts to make all components in the column 103 * as wide as the widest component. 104 * If that fails, it aligns them horizontally 105 * according to their X alignments. For {@code PAGE_AXIS} layout, 106 * horizontal alignment is done based on the leading edge of the component. 107 * In other words, an X alignment value of 0.0 means the left edge of a 108 * component if the container's {@code ComponentOrientation} is left to 109 * right and it means the right edge of the component otherwise. 110 * <p> 111 * Instead of using BoxLayout directly, many programs use the Box class. 112 * The Box class is a lightweight container that uses a BoxLayout. 113 * It also provides handy methods to help you use BoxLayout well. 114 * Adding components to multiple nested boxes is a powerful way to get 115 * the arrangement you want. 116 * <p> 117 * For further information and examples see 118 * <a 119 href="http://docs.oracle.com/javase/tutorial/uiswing/layout/box.html">How to Use BoxLayout</a>, 120 * a section in <em>The Java Tutorial.</em> 121 * <p> 122 * <strong>Warning:</strong> 123 * Serialized objects of this class will not be compatible with 124 * future Swing releases. The current serialization support is 125 * appropriate for short term storage or RMI between applications running 126 * the same version of Swing. As of 1.4, support for long term storage 127 * of all JavaBeans™ 128 * has been added to the {@code java.beans} package. 129 * Please see {@link java.beans.XMLEncoder}. 130 * 131 * @see Box 132 * @see java.awt.ComponentOrientation 133 * @see JComponent#getAlignmentX 134 * @see JComponent#getAlignmentY 135 * 136 * @author Timothy Prinzing 137 * @since 1.2 138 */ 139 @SuppressWarnings("serial") 140 public class BoxLayout implements LayoutManager2, Serializable { 141 142 /** 143 * Specifies that components should be laid out left to right. 144 */ 145 public static final int X_AXIS = 0; 146 147 /** 148 * Specifies that components should be laid out top to bottom. 149 */ 150 public static final int Y_AXIS = 1; 151 152 /** 153 * Specifies that components should be laid out in the direction of 154 * a line of text as determined by the target container's 155 * {@code ComponentOrientation} property. 156 */ 157 public static final int LINE_AXIS = 2; 158 159 /** 160 * Specifies that components should be laid out in the direction that 161 * lines flow across a page as determined by the target container's 162 * {@code ComponentOrientation} property. 163 */ 164 public static final int PAGE_AXIS = 3; 165 166 /** 167 * Creates a layout manager that will lay out components along the 168 * given axis. 169 * 170 * @param target the container that needs to be laid out 171 * @param axis the axis to lay out components along. Can be one of: 172 * {@code BoxLayout.X_AXIS, BoxLayout.Y_AXIS, 173 * BoxLayout.LINE_AXIS} or {@code BoxLayout.PAGE_AXIS} 174 * 175 * @exception AWTError if the value of {@code axis} is invalid 176 */ 177 @ConstructorProperties({"target", "axis"}) 178 public BoxLayout(Container target, int axis) { 179 if (axis != X_AXIS && axis != Y_AXIS && 180 axis != LINE_AXIS && axis != PAGE_AXIS) { 181 throw new AWTError("Invalid axis"); 182 } 183 this.axis = axis; 184 this.target = target; 185 } 186 187 /** 188 * Constructs a BoxLayout that 189 * produces debugging messages. 190 * 191 * @param target the container that needs to be laid out 192 * @param axis the axis to lay out components along. Can be one of: 193 * {@code BoxLayout.X_AXIS, BoxLayout.Y_AXIS, 194 * BoxLayout.LINE_AXIS} or {@code BoxLayout.PAGE_AXIS} 195 * 196 * @param dbg the stream to which debugging messages should be sent, 197 * null if none 198 */ 199 BoxLayout(Container target, int axis, PrintStream dbg) { 200 this(target, axis); 201 this.dbg = dbg; 202 } 203 204 /** 205 * Returns the container that uses this layout manager. 206 * 207 * @return the container that uses this layout manager 208 * 209 * @since 1.6 210 */ 211 public final Container getTarget() { 212 return this.target; 213 } 214 215 /** 216 * Returns the axis that was used to lay out components. 217 * Returns one of: 218 * {@code BoxLayout.X_AXIS, BoxLayout.Y_AXIS, 219 * BoxLayout.LINE_AXIS} or {@code BoxLayout.PAGE_AXIS} 220 * 221 * @return the axis that was used to lay out components 222 * 223 * @since 1.6 224 */ 225 public final int getAxis() { 226 return this.axis; 227 } 228 229 /** 230 * Indicates that a child has changed its layout related information, 231 * and thus any cached calculations should be flushed. 232 * <p> 233 * This method is called by AWT when the invalidate method is called 234 * on the Container. Since the invalidate method may be called 235 * asynchronously to the event thread, this method may be called 236 * asynchronously. 237 * 238 * @param target the affected container 239 * 240 * @exception AWTError if the target isn't the container specified to the 241 * BoxLayout constructor 242 */ 243 public synchronized void invalidateLayout(Container target) { 244 checkContainer(target); 245 xChildren = null; 246 yChildren = null; 247 xTotal = null; 248 yTotal = null; 249 } 250 251 /** 252 * Not used by this class. 253 * 254 * @param name the name of the component 255 * @param comp the component 256 */ 257 public void addLayoutComponent(String name, Component comp) { 258 invalidateLayout(comp.getParent()); 259 } 260 261 /** 262 * Not used by this class. 263 * 264 * @param comp the component 265 */ 266 public void removeLayoutComponent(Component comp) { 267 invalidateLayout(comp.getParent()); 268 } 269 270 /** 271 * Not used by this class. 272 * 273 * @param comp the component 274 * @param constraints constraints 275 */ 276 public void addLayoutComponent(Component comp, Object constraints) { 277 invalidateLayout(comp.getParent()); 278 } 279 280 /** 281 * Returns the preferred dimensions for this layout, given the components 282 * in the specified target container. 283 * 284 * @param target the container that needs to be laid out 285 * @return the dimensions >= 0 && <= Integer.MAX_VALUE 286 * @exception AWTError if the target isn't the container specified to the 287 * BoxLayout constructor 288 * @see Container 289 * @see #minimumLayoutSize 290 * @see #maximumLayoutSize 291 */ 292 public Dimension preferredLayoutSize(Container target) { 293 Dimension size; 294 synchronized(this) { 295 checkContainer(target); 296 checkRequests(); 297 size = new Dimension(xTotal.preferred, yTotal.preferred); 298 } 299 300 Insets insets = target.getInsets(); 301 size.width = (int) Math.min((long) size.width + (long) insets.left + (long) insets.right, Integer.MAX_VALUE); 302 size.height = (int) Math.min((long) size.height + (long) insets.top + (long) insets.bottom, Integer.MAX_VALUE); 303 return size; 304 } 305 306 /** 307 * Returns the minimum dimensions needed to lay out the components 308 * contained in the specified target container. 309 * 310 * @param target the container that needs to be laid out 311 * @return the dimensions >= 0 && <= Integer.MAX_VALUE 312 * @exception AWTError if the target isn't the container specified to the 313 * BoxLayout constructor 314 * @see #preferredLayoutSize 315 * @see #maximumLayoutSize 316 */ 317 public Dimension minimumLayoutSize(Container target) { 318 Dimension size; 319 synchronized(this) { 320 checkContainer(target); 321 checkRequests(); 322 size = new Dimension(xTotal.minimum, yTotal.minimum); 323 } 324 325 Insets insets = target.getInsets(); 326 size.width = (int) Math.min((long) size.width + (long) insets.left + (long) insets.right, Integer.MAX_VALUE); 327 size.height = (int) Math.min((long) size.height + (long) insets.top + (long) insets.bottom, Integer.MAX_VALUE); 328 return size; 329 } 330 331 /** 332 * Returns the maximum dimensions the target container can use 333 * to lay out the components it contains. 334 * 335 * @param target the container that needs to be laid out 336 * @return the dimensions >= 0 && <= Integer.MAX_VALUE 337 * @exception AWTError if the target isn't the container specified to the 338 * BoxLayout constructor 339 * @see #preferredLayoutSize 340 * @see #minimumLayoutSize 341 */ 342 public Dimension maximumLayoutSize(Container target) { 343 Dimension size; 344 synchronized(this) { 345 checkContainer(target); 346 checkRequests(); 347 size = new Dimension(xTotal.maximum, yTotal.maximum); 348 } 349 350 Insets insets = target.getInsets(); 351 size.width = (int) Math.min((long) size.width + (long) insets.left + (long) insets.right, Integer.MAX_VALUE); 352 size.height = (int) Math.min((long) size.height + (long) insets.top + (long) insets.bottom, Integer.MAX_VALUE); 353 return size; 354 } 355 356 /** 357 * Returns the alignment along the X axis for the container. 358 * If the box is horizontal, the default 359 * alignment will be returned. Otherwise, the alignment needed 360 * to place the children along the X axis will be returned. 361 * 362 * @param target the container 363 * @return the alignment >= 0.0f && <= 1.0f 364 * @exception AWTError if the target isn't the container specified to the 365 * BoxLayout constructor 366 */ 367 public synchronized float getLayoutAlignmentX(Container target) { 368 checkContainer(target); 369 checkRequests(); 370 return xTotal.alignment; 371 } 372 373 /** 374 * Returns the alignment along the Y axis for the container. 375 * If the box is vertical, the default 376 * alignment will be returned. Otherwise, the alignment needed 377 * to place the children along the Y axis will be returned. 378 * 379 * @param target the container 380 * @return the alignment >= 0.0f && <= 1.0f 381 * @exception AWTError if the target isn't the container specified to the 382 * BoxLayout constructor 383 */ 384 public synchronized float getLayoutAlignmentY(Container target) { 385 checkContainer(target); 386 checkRequests(); 387 return yTotal.alignment; 388 } 389 390 /** 391 * Called by the AWT <!-- XXX CHECK! --> when the specified container 392 * needs to be laid out. 393 * 394 * @param target the container to lay out 395 * 396 * @exception AWTError if the target isn't the container specified to the 397 * BoxLayout constructor 398 */ 399 public void layoutContainer(Container target) { 400 checkContainer(target); 401 int nChildren = target.getComponentCount(); 402 int[] xOffsets = new int[nChildren]; 403 int[] xSpans = new int[nChildren]; 404 int[] yOffsets = new int[nChildren]; 405 int[] ySpans = new int[nChildren]; 406 407 Dimension alloc = target.getSize(); 408 Insets in = target.getInsets(); 409 alloc.width -= in.left + in.right; 410 alloc.height -= in.top + in.bottom; 411 412 // Resolve axis to an absolute value (either X_AXIS or Y_AXIS) 413 ComponentOrientation o = target.getComponentOrientation(); 414 int absoluteAxis = resolveAxis( axis, o ); 415 boolean ltr = (absoluteAxis != axis) ? o.isLeftToRight() : true; 416 417 418 // determine the child placements 419 synchronized(this) { 420 checkRequests(); 421 422 if (absoluteAxis == X_AXIS) { 423 SizeRequirements.calculateTiledPositions(alloc.width, xTotal, 424 xChildren, xOffsets, 425 xSpans, ltr); 426 SizeRequirements.calculateAlignedPositions(alloc.height, yTotal, 427 yChildren, yOffsets, 428 ySpans); 429 } else { 430 SizeRequirements.calculateAlignedPositions(alloc.width, xTotal, 431 xChildren, xOffsets, 432 xSpans, ltr); 433 SizeRequirements.calculateTiledPositions(alloc.height, yTotal, 434 yChildren, yOffsets, 435 ySpans); 436 } 437 } 438 439 // flush changes to the container 440 for (int i = 0; i < nChildren; i++) { 441 Component c = target.getComponent(i); 442 c.setBounds((int) Math.min((long) in.left + (long) xOffsets[i], Integer.MAX_VALUE), 443 (int) Math.min((long) in.top + (long) yOffsets[i], Integer.MAX_VALUE), 444 xSpans[i], ySpans[i]); 445 446 } 447 if (dbg != null) { 448 for (int i = 0; i < nChildren; i++) { 449 Component c = target.getComponent(i); 450 dbg.println(c.toString()); 451 dbg.println("X: " + xChildren[i]); 452 dbg.println("Y: " + yChildren[i]); 453 } 454 } 455 456 } 457 458 void checkContainer(Container target) { 459 if (this.target != target) { 460 throw new AWTError("BoxLayout can't be shared"); 461 } 462 } 463 464 void checkRequests() { 465 if (xChildren == null || yChildren == null) { 466 // The requests have been invalidated... recalculate 467 // the request information. 468 int n = target.getComponentCount(); 469 xChildren = new SizeRequirements[n]; 470 yChildren = new SizeRequirements[n]; 471 for (int i = 0; i < n; i++) { 472 Component c = target.getComponent(i); 473 if (!c.isVisible()) { 474 xChildren[i] = new SizeRequirements(0,0,0, c.getAlignmentX()); 475 yChildren[i] = new SizeRequirements(0,0,0, c.getAlignmentY()); 476 continue; 477 } 478 Dimension min = c.getMinimumSize(); 479 Dimension typ = c.getPreferredSize(); 480 Dimension max = c.getMaximumSize(); 481 xChildren[i] = new SizeRequirements(min.width, typ.width, 482 max.width, 483 c.getAlignmentX()); 484 yChildren[i] = new SizeRequirements(min.height, typ.height, 485 max.height, 486 c.getAlignmentY()); 487 } 488 489 // Resolve axis to an absolute value (either X_AXIS or Y_AXIS) 490 int absoluteAxis = resolveAxis(axis,target.getComponentOrientation()); 491 492 if (absoluteAxis == X_AXIS) { 493 xTotal = SizeRequirements.getTiledSizeRequirements(xChildren); 494 yTotal = SizeRequirements.getAlignedSizeRequirements(yChildren); 495 } else { 496 xTotal = SizeRequirements.getAlignedSizeRequirements(xChildren); 497 yTotal = SizeRequirements.getTiledSizeRequirements(yChildren); 498 } 499 } 500 } 501 502 /** 503 * Given one of the 4 axis values, resolve it to an absolute axis. 504 * The relative axis values, PAGE_AXIS and LINE_AXIS are converted 505 * to their absolute couterpart given the target's ComponentOrientation 506 * value. The absolute axes, X_AXIS and Y_AXIS are returned unmodified. 507 * 508 * @param axis the axis to resolve 509 * @param o the ComponentOrientation to resolve against 510 * @return the resolved axis 511 */ 512 private int resolveAxis( int axis, ComponentOrientation o ) { 513 int absoluteAxis; 514 if( axis == LINE_AXIS ) { 515 absoluteAxis = o.isHorizontal() ? X_AXIS : Y_AXIS; 516 } else if( axis == PAGE_AXIS ) { 517 absoluteAxis = o.isHorizontal() ? Y_AXIS : X_AXIS; 518 } else { 519 absoluteAxis = axis; 520 } 521 return absoluteAxis; 522 } 523 524 525 private int axis; 526 private Container target; 527 528 private transient SizeRequirements[] xChildren; 529 private transient SizeRequirements[] yChildren; 530 private transient SizeRequirements xTotal; 531 private transient SizeRequirements yTotal; 532 533 private transient PrintStream dbg; 534 }