1 /* 2 * Copyright (c) 1997, 2019, 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 javax.swing; 26 27 import java.awt.Component; 28 import java.util.ArrayList; 29 import java.util.Hashtable; 30 import java.awt.Color; 31 import java.awt.Graphics; 32 import java.awt.Rectangle; 33 import java.beans.JavaBean; 34 import java.beans.BeanProperty; 35 36 import sun.awt.SunToolkit; 37 38 import javax.accessibility.*; 39 40 /** 41 * <code>JLayeredPane</code> adds depth to a JFC/Swing container, 42 * allowing components to overlap each other when needed. 43 * An <code>Integer</code> object specifies each component's depth in the 44 * container, where higher-numbered components sit "on top" of other 45 * components. 46 * For task-oriented documentation and examples of using layered panes see 47 * <a href="https://docs.oracle.com/javase/tutorial/uiswing/components/layeredpane.html">How to Use a Layered Pane</a>, 48 * a section in <em>The Java Tutorial</em>. 49 * 50 * <div style="float:right;text-align:center"> 51 * <p><b>Example:</b> 52 * <p><img src="doc-files/JLayeredPane-1.gif" 53 * alt="The following text describes this image." 54 * width="269" height="264"> 55 * </div> 56 * For convenience, <code>JLayeredPane</code> divides the depth-range 57 * into several different layers. Putting a component into one of those 58 * layers makes it easy to ensure that components overlap properly, 59 * without having to worry about specifying numbers for specific depths: 60 * <DL> 61 * <DT>DEFAULT_LAYER</DT> 62 * <DD>The standard layer, where most components go. This the bottommost 63 * layer. 64 * <DT>PALETTE_LAYER</DT> 65 * <DD>The palette layer sits over the default layer. Useful for floating 66 * toolbars and palettes, so they can be positioned above other components. 67 * <DT>MODAL_LAYER</DT> 68 * <DD>The layer used for modal dialogs. They will appear on top of any 69 * toolbars, palettes, or standard components in the container. 70 * <DT>POPUP_LAYER</DT> 71 * <DD>The popup layer displays above dialogs. That way, the popup windows 72 * associated with combo boxes, tooltips, and other help text will appear 73 * above the component, palette, or dialog that generated them. 74 * <DT>DRAG_LAYER</DT> 75 * <DD>When dragging a component, reassigning it to the drag layer ensures 76 * that it is positioned over every other component in the container. When 77 * finished dragging, it can be reassigned to its normal layer. 78 * </DL> 79 * The <code>JLayeredPane</code> methods <code>moveToFront(Component)</code>, 80 * <code>moveToBack(Component)</code> and <code>setPosition</code> can be used 81 * to reposition a component within its layer. The <code>setLayer</code> method 82 * can also be used to change the component's current layer. 83 * 84 * <h2>Details</h2> 85 * <code>JLayeredPane</code> manages its list of children like 86 * <code>Container</code>, but allows for the definition of a several 87 * layers within itself. Children in the same layer are managed exactly 88 * like the normal <code>Container</code> object, 89 * with the added feature that when children components overlap, children 90 * in higher layers display above the children in lower layers. 91 * <p> 92 * Each layer is a distinct integer number. The layer attribute can be set 93 * on a <code>Component</code> by passing an <code>Integer</code> 94 * object during the add call.<br> For example: 95 * <PRE> 96 * layeredPane.add(child, JLayeredPane.DEFAULT_LAYER); 97 * or 98 * layeredPane.add(child, Integer.valueOf.valueOf(10)); 99 * </PRE> 100 * The layer attribute can also be set on a Component by calling<PRE> 101 * layeredPaneParent.setLayer(child, 10)</PRE> 102 * on the <code>JLayeredPane</code> that is the parent of component. The layer 103 * should be set <i>before</i> adding the child to the parent. 104 * <p> 105 * Higher number layers display above lower number layers. So, using 106 * numbers for the layers and letters for individual components, a 107 * representative list order would look like this:<PRE> 108 * 5a, 5b, 5c, 2a, 2b, 2c, 1a </PRE> 109 * where the leftmost components are closest to the top of the display. 110 * <p> 111 * A component can be moved to the top or bottom position within its 112 * layer by calling <code>moveToFront</code> or <code>moveToBack</code>. 113 * <p> 114 * The position of a component within a layer can also be specified directly. 115 * Valid positions range from 0 up to one less than the number of 116 * components in that layer. A value of -1 indicates the bottommost 117 * position. A value of 0 indicates the topmost position. Unlike layer 118 * numbers, higher position values are <i>lower</i> in the display. 119 * <blockquote> 120 * <b>Note:</b> This sequence (defined by java.awt.Container) is the reverse 121 * of the layer numbering sequence. Usually though, you will use <code>moveToFront</code>, 122 * <code>moveToBack</code>, and <code>setLayer</code>. 123 * </blockquote> 124 * Here are some examples using the method add(Component, layer, position): 125 * Calling add(5x, 5, -1) results in:<PRE> 126 * 5a, 5b, 5c, 5x, 2a, 2b, 2c, 1a </PRE> 127 * 128 * Calling add(5z, 5, 2) results in:<PRE> 129 * 5a, 5b, 5z, 5c, 5x, 2a, 2b, 2c, 1a </PRE> 130 * 131 * Calling add(3a, 3, 7) results in:<PRE> 132 * 5a, 5b, 5z, 5c, 5x, 3a, 2a, 2b, 2c, 1a </PRE> 133 * 134 * Using normal paint/event mechanics results in 1a appearing at the bottom 135 * and 5a being above all other components. 136 * <p> 137 * <b>Note:</b> that these layers are simply a logical construct and LayoutManagers 138 * will affect all child components of this container without regard for 139 * layer settings. 140 * <p> 141 * <strong>Warning:</strong> Swing is not thread safe. For more 142 * information see <a 143 * href="package-summary.html#threading">Swing's Threading 144 * Policy</a>. 145 * <p> 146 * <strong>Warning:</strong> 147 * Serialized objects of this class will not be compatible with 148 * future Swing releases. The current serialization support is 149 * appropriate for short term storage or RMI between applications running 150 * the same version of Swing. As of 1.4, support for long term storage 151 * of all JavaBeans™ 152 * has been added to the <code>java.beans</code> package. 153 * Please see {@link java.beans.XMLEncoder}. 154 * 155 * @author David Kloba 156 * @since 1.2 157 */ 158 @JavaBean(defaultProperty = "accessibleContext") 159 @SuppressWarnings("serial") 160 public class JLayeredPane extends JComponent implements Accessible { 161 /// Watch the values in getObjectForLayer() 162 /** Convenience object defining the Default layer. Equivalent to Integer.valueOf(0).*/ 163 public static final Integer DEFAULT_LAYER = 0; 164 /** Convenience object defining the Palette layer. Equivalent to Integer.valueOf(100).*/ 165 public static final Integer PALETTE_LAYER = 100; 166 /** Convenience object defining the Modal layer. Equivalent to Integer.valueOf(200).*/ 167 public static final Integer MODAL_LAYER = 200; 168 /** Convenience object defining the Popup layer. Equivalent to Integer.valueOf(300).*/ 169 public static final Integer POPUP_LAYER = 300; 170 /** Convenience object defining the Drag layer. Equivalent to Integer.valueOf(400).*/ 171 public static final Integer DRAG_LAYER = 400; 172 /** Convenience object defining the Frame Content layer. 173 * This layer is normally only use to position the contentPane and menuBar 174 * components of JFrame. 175 * Equivalent to Integer.valueOf(-30000). 176 * @see JFrame 177 */ 178 public static final Integer FRAME_CONTENT_LAYER = -30000; 179 180 /** Bound property */ 181 public static final String LAYER_PROPERTY = "layeredContainerLayer"; 182 // Hashtable to store layer values for non-JComponent components 183 private Hashtable<Component,Integer> componentToLayer; 184 private boolean optimizedDrawingPossible = true; 185 186 187 ////////////////////////////////////////////////////////////////////////////// 188 //// Container Override methods 189 ////////////////////////////////////////////////////////////////////////////// 190 /** Create a new JLayeredPane */ 191 public JLayeredPane() { 192 setLayout(null); 193 } 194 195 private void validateOptimizedDrawing() { 196 boolean layeredComponentFound = false; 197 synchronized(getTreeLock()) { 198 Integer layer; 199 200 for (Component c : getComponents()) { 201 layer = null; 202 203 if(SunToolkit.isInstanceOf(c, "javax.swing.JInternalFrame") || 204 (c instanceof JComponent && 205 (layer = (Integer)((JComponent)c). 206 getClientProperty(LAYER_PROPERTY)) != null)) 207 { 208 if(layer != null && layer.equals(FRAME_CONTENT_LAYER)) 209 continue; 210 layeredComponentFound = true; 211 break; 212 } 213 } 214 } 215 216 if(layeredComponentFound) 217 optimizedDrawingPossible = false; 218 else 219 optimizedDrawingPossible = true; 220 } 221 222 protected void addImpl(Component comp, Object constraints, int index) { 223 int layer; 224 int pos; 225 226 if(constraints instanceof Integer) { 227 layer = ((Integer)constraints).intValue(); 228 setLayer(comp, layer); 229 } else 230 layer = getLayer(comp); 231 232 pos = insertIndexForLayer(layer, index); 233 super.addImpl(comp, constraints, pos); 234 comp.validate(); 235 comp.repaint(); 236 validateOptimizedDrawing(); 237 } 238 239 /** 240 * Remove the indexed component from this pane. 241 * This is the absolute index, ignoring layers. 242 * 243 * @param index an int specifying the component to remove 244 * @see #getIndexOf 245 */ 246 public void remove(int index) { 247 Component c = getComponent(index); 248 super.remove(index); 249 if (c != null && !(c instanceof JComponent)) { 250 getComponentToLayer().remove(c); 251 } 252 validateOptimizedDrawing(); 253 } 254 255 /** 256 * Removes all the components from this container. 257 * 258 * @since 1.5 259 */ 260 public void removeAll() { 261 Component[] children = getComponents(); 262 Hashtable<Component, Integer> cToL = getComponentToLayer(); 263 for (int counter = children.length - 1; counter >= 0; counter--) { 264 Component c = children[counter]; 265 if (c != null && !(c instanceof JComponent)) { 266 cToL.remove(c); 267 } 268 } 269 super.removeAll(); 270 } 271 272 /** 273 * Returns false if components in the pane can overlap, which makes 274 * optimized drawing impossible. Otherwise, returns true. 275 * 276 * @return false if components can overlap, else true 277 * @see JComponent#isOptimizedDrawingEnabled 278 */ 279 @BeanProperty(bound = false) 280 public boolean isOptimizedDrawingEnabled() { 281 return optimizedDrawingPossible; 282 } 283 284 285 ////////////////////////////////////////////////////////////////////////////// 286 //// New methods for managing layers 287 ////////////////////////////////////////////////////////////////////////////// 288 /** Sets the layer property on a JComponent. This method does not cause 289 * any side effects like setLayer() (painting, add/remove, etc). 290 * Normally you should use the instance method setLayer(), in order to 291 * get the desired side-effects (like repainting). 292 * 293 * @param c the JComponent to move 294 * @param layer an int specifying the layer to move it to 295 * @see #setLayer 296 */ 297 public static void putLayer(JComponent c, int layer) { 298 /// MAKE SURE THIS AND setLayer(Component c, int layer, int position) are SYNCED 299 c.putClientProperty(LAYER_PROPERTY, layer); 300 } 301 302 /** Gets the layer property for a JComponent, it 303 * does not cause any side effects like setLayer(). (painting, add/remove, etc) 304 * Normally you should use the instance method getLayer(). 305 * 306 * @param c the JComponent to check 307 * @return an int specifying the component's layer 308 */ 309 public static int getLayer(JComponent c) { 310 Integer i; 311 if((i = (Integer)c.getClientProperty(LAYER_PROPERTY)) != null) 312 return i.intValue(); 313 return DEFAULT_LAYER.intValue(); 314 } 315 316 /** Convenience method that returns the first JLayeredPane which 317 * contains the specified component. Note that all JFrames have a 318 * JLayeredPane at their root, so any component in a JFrame will 319 * have a JLayeredPane parent. 320 * 321 * @param c the Component to check 322 * @return the JLayeredPane that contains the component, or 323 * null if no JLayeredPane is found in the component 324 * hierarchy 325 * @see JFrame 326 * @see JRootPane 327 */ 328 public static JLayeredPane getLayeredPaneAbove(Component c) { 329 if(c == null) return null; 330 331 Component parent = c.getParent(); 332 while(parent != null && !(parent instanceof JLayeredPane)) 333 parent = parent.getParent(); 334 return (JLayeredPane)parent; 335 } 336 337 /** Sets the layer attribute on the specified component, 338 * making it the bottommost component in that layer. 339 * Should be called before adding to parent. 340 * 341 * @param c the Component to set the layer for 342 * @param layer an int specifying the layer to set, where 343 * lower numbers are closer to the bottom 344 */ 345 public void setLayer(Component c, int layer) { 346 setLayer(c, layer, -1); 347 } 348 349 /** Sets the layer attribute for the specified component and 350 * also sets its position within that layer. 351 * 352 * @param c the Component to set the layer for 353 * @param layer an int specifying the layer to set, where 354 * lower numbers are closer to the bottom 355 * @param position an int specifying the position within the 356 * layer, where 0 is the topmost position and -1 357 * is the bottommost position 358 */ 359 public void setLayer(Component c, int layer, int position) { 360 Integer layerObj; 361 layerObj = getObjectForLayer(layer); 362 363 if(layer == getLayer(c) && position == getPosition(c)) { 364 repaint(c.getBounds()); 365 return; 366 } 367 368 /// MAKE SURE THIS AND putLayer(JComponent c, int layer) are SYNCED 369 if(c instanceof JComponent) 370 ((JComponent)c).putClientProperty(LAYER_PROPERTY, layerObj); 371 else 372 getComponentToLayer().put(c, layerObj); 373 374 if(c.getParent() == null || c.getParent() != this) { 375 repaint(c.getBounds()); 376 return; 377 } 378 379 int index = insertIndexForLayer(c, layer, position); 380 381 setComponentZOrder(c, index); 382 repaint(c.getBounds()); 383 } 384 385 /** 386 * Returns the layer attribute for the specified Component. 387 * 388 * @param c the Component to check 389 * @return an int specifying the component's current layer 390 */ 391 public int getLayer(Component c) { 392 Integer i; 393 if(c instanceof JComponent) 394 i = (Integer)((JComponent)c).getClientProperty(LAYER_PROPERTY); 395 else 396 i = getComponentToLayer().get(c); 397 398 if(i == null) 399 return DEFAULT_LAYER.intValue(); 400 return i.intValue(); 401 } 402 403 /** 404 * Returns the index of the specified Component. 405 * This is the absolute index, ignoring layers. 406 * Index numbers, like position numbers, have the topmost component 407 * at index zero. Larger numbers are closer to the bottom. 408 * 409 * @param c the Component to check 410 * @return an int specifying the component's index 411 */ 412 public int getIndexOf(Component c) { 413 int i, count; 414 415 count = getComponentCount(); 416 for(i = 0; i < count; i++) { 417 if(c == getComponent(i)) 418 return i; 419 } 420 return -1; 421 } 422 /** 423 * Moves the component to the top of the components in its current layer 424 * (position 0). 425 * 426 * @param c the Component to move 427 * @see #setPosition(Component, int) 428 */ 429 public void moveToFront(Component c) { 430 setPosition(c, 0); 431 } 432 433 /** 434 * Moves the component to the bottom of the components in its current layer 435 * (position -1). 436 * 437 * @param c the Component to move 438 * @see #setPosition(Component, int) 439 */ 440 public void moveToBack(Component c) { 441 setPosition(c, -1); 442 } 443 444 /** 445 * Moves the component to <code>position</code> within its current layer, 446 * where 0 is the topmost position within the layer and -1 is the bottommost 447 * position. 448 * <p> 449 * <b>Note:</b> Position numbering is defined by java.awt.Container, and 450 * is the opposite of layer numbering. Lower position numbers are closer 451 * to the top (0 is topmost), and higher position numbers are closer to 452 * the bottom. 453 * 454 * @param c the Component to move 455 * @param position an int in the range -1..N-1, where N is the number of 456 * components in the component's current layer 457 */ 458 public void setPosition(Component c, int position) { 459 setLayer(c, getLayer(c), position); 460 } 461 462 /** 463 * Get the relative position of the component within its layer. 464 * 465 * @param c the Component to check 466 * @return an int giving the component's position, where 0 is the 467 * topmost position and the highest index value = the count 468 * count of components at that layer, minus 1 469 * 470 * @see #getComponentCountInLayer 471 */ 472 public int getPosition(Component c) { 473 int i, startLayer, curLayer, startLocation, pos = 0; 474 475 getComponentCount(); 476 startLocation = getIndexOf(c); 477 478 if(startLocation == -1) 479 return -1; 480 481 startLayer = getLayer(c); 482 for(i = startLocation - 1; i >= 0; i--) { 483 curLayer = getLayer(getComponent(i)); 484 if(curLayer == startLayer) 485 pos++; 486 else 487 return pos; 488 } 489 return pos; 490 } 491 492 /** Returns the highest layer value from all current children. 493 * Returns 0 if there are no children. 494 * 495 * @return an int indicating the layer of the topmost component in the 496 * pane, or zero if there are no children 497 */ 498 public int highestLayer() { 499 if(getComponentCount() > 0) 500 return getLayer(getComponent(0)); 501 return 0; 502 } 503 504 /** Returns the lowest layer value from all current children. 505 * Returns 0 if there are no children. 506 * 507 * @return an int indicating the layer of the bottommost component in the 508 * pane, or zero if there are no children 509 */ 510 public int lowestLayer() { 511 int count = getComponentCount(); 512 if(count > 0) 513 return getLayer(getComponent(count-1)); 514 return 0; 515 } 516 517 /** 518 * Returns the number of children currently in the specified layer. 519 * 520 * @param layer an int specifying the layer to check 521 * @return an int specifying the number of components in that layer 522 */ 523 public int getComponentCountInLayer(int layer) { 524 int i, count, curLayer; 525 int layerCount = 0; 526 527 count = getComponentCount(); 528 for(i = 0; i < count; i++) { 529 curLayer = getLayer(getComponent(i)); 530 if(curLayer == layer) { 531 layerCount++; 532 /// Short circut the counting when we have them all 533 } else if(layerCount > 0 || curLayer < layer) { 534 break; 535 } 536 } 537 538 return layerCount; 539 } 540 541 /** 542 * Returns an array of the components in the specified layer. 543 * 544 * @param layer an int specifying the layer to check 545 * @return an array of Components contained in that layer 546 */ 547 public Component[] getComponentsInLayer(int layer) { 548 int i, count, curLayer; 549 int layerCount = 0; 550 Component[] results; 551 552 results = new Component[getComponentCountInLayer(layer)]; 553 count = getComponentCount(); 554 for(i = 0; i < count; i++) { 555 curLayer = getLayer(getComponent(i)); 556 if(curLayer == layer) { 557 results[layerCount++] = getComponent(i); 558 /// Short circut the counting when we have them all 559 } else if(layerCount > 0 || curLayer < layer) { 560 break; 561 } 562 } 563 564 return results; 565 } 566 567 /** 568 * Paints this JLayeredPane within the specified graphics context. 569 * 570 * @param g the Graphics context within which to paint 571 */ 572 public void paint(Graphics g) { 573 if(isOpaque()) { 574 Rectangle r = g.getClipBounds(); 575 Color c = getBackground(); 576 if(c == null) 577 c = Color.lightGray; 578 g.setColor(c); 579 if (r != null) { 580 g.fillRect(r.x, r.y, r.width, r.height); 581 } 582 else { 583 g.fillRect(0, 0, getWidth(), getHeight()); 584 } 585 } 586 super.paint(g); 587 } 588 589 ////////////////////////////////////////////////////////////////////////////// 590 //// Implementation Details 591 ////////////////////////////////////////////////////////////////////////////// 592 593 /** 594 * Returns the hashtable that maps components to layers. 595 * 596 * @return the Hashtable used to map components to their layers 597 */ 598 protected Hashtable<Component,Integer> getComponentToLayer() { 599 if(componentToLayer == null) 600 componentToLayer = new Hashtable<Component,Integer>(4); 601 return componentToLayer; 602 } 603 604 /** 605 * Returns the Integer object associated with a specified layer. 606 * 607 * @param layer an int specifying the layer 608 * @return an Integer object for that layer 609 */ 610 protected Integer getObjectForLayer(int layer) { 611 switch(layer) { 612 case 0: 613 return DEFAULT_LAYER; 614 case 100: 615 return PALETTE_LAYER; 616 case 200: 617 return MODAL_LAYER; 618 case 300: 619 return POPUP_LAYER; 620 case 400: 621 return DRAG_LAYER; 622 default: 623 return layer; 624 } 625 } 626 627 /** 628 * Primitive method that determines the proper location to 629 * insert a new child based on layer and position requests. 630 * 631 * @param layer an int specifying the layer 632 * @param position an int specifying the position within the layer 633 * @return an int giving the (absolute) insertion-index 634 * 635 * @see #getIndexOf 636 */ 637 protected int insertIndexForLayer(int layer, int position) { 638 return insertIndexForLayer(null, layer, position); 639 } 640 641 /** 642 * This method is an extended version of insertIndexForLayer() 643 * to support setLayer which uses Container.setZOrder which does 644 * not remove the component from the containment hierarchy though 645 * we need to ignore it when calculating the insertion index. 646 * 647 * @param comp component to ignore when determining index 648 * @param layer an int specifying the layer 649 * @param position an int specifying the position within the layer 650 * @return an int giving the (absolute) insertion-index 651 * 652 * @see #getIndexOf 653 */ 654 private int insertIndexForLayer(Component comp, int layer, int position) { 655 int i, count, curLayer; 656 int layerStart = -1; 657 int layerEnd = -1; 658 int componentCount = getComponentCount(); 659 660 ArrayList<Component> compList = 661 new ArrayList<Component>(componentCount); 662 for (int index = 0; index < componentCount; index++) { 663 if (getComponent(index) != comp) { 664 compList.add(getComponent(index)); 665 } 666 } 667 668 count = compList.size(); 669 for (i = 0; i < count; i++) { 670 curLayer = getLayer(compList.get(i)); 671 if (layerStart == -1 && curLayer == layer) { 672 layerStart = i; 673 } 674 if (curLayer < layer) { 675 if (i == 0) { 676 // layer is greater than any current layer 677 // [ ASSERT(layer > highestLayer()) ] 678 layerStart = 0; 679 layerEnd = 0; 680 } else { 681 layerEnd = i; 682 } 683 break; 684 } 685 } 686 687 // layer requested is lower than any current layer 688 // [ ASSERT(layer < lowestLayer()) ] 689 // put it on the bottom of the stack 690 if (layerStart == -1 && layerEnd == -1) 691 return count; 692 693 // In the case of a single layer entry handle the degenerative cases 694 if (layerStart != -1 && layerEnd == -1) 695 layerEnd = count; 696 697 if (layerEnd != -1 && layerStart == -1) 698 layerStart = layerEnd; 699 700 // If we are adding to the bottom, return the last element 701 if (position == -1) 702 return layerEnd; 703 704 // Otherwise make sure the requested position falls in the 705 // proper range 706 if (position > -1 && layerStart + position <= layerEnd) 707 return layerStart + position; 708 709 // Otherwise return the end of the layer 710 return layerEnd; 711 } 712 713 /** 714 * Returns a string representation of this JLayeredPane. This method 715 * is intended to be used only for debugging purposes, and the 716 * content and format of the returned string may vary between 717 * implementations. The returned string may be empty but may not 718 * be <code>null</code>. 719 * 720 * @return a string representation of this JLayeredPane. 721 */ 722 protected String paramString() { 723 String optimizedDrawingPossibleString = (optimizedDrawingPossible ? 724 "true" : "false"); 725 726 return super.paramString() + 727 ",optimizedDrawingPossible=" + optimizedDrawingPossibleString; 728 } 729 730 ///////////////// 731 // Accessibility support 732 //////////////// 733 734 /** 735 * Gets the AccessibleContext associated with this JLayeredPane. 736 * For layered panes, the AccessibleContext takes the form of an 737 * AccessibleJLayeredPane. 738 * A new AccessibleJLayeredPane instance is created if necessary. 739 * 740 * @return an AccessibleJLayeredPane that serves as the 741 * AccessibleContext of this JLayeredPane 742 */ 743 @BeanProperty(bound = false) 744 public AccessibleContext getAccessibleContext() { 745 if (accessibleContext == null) { 746 accessibleContext = new AccessibleJLayeredPane(); 747 } 748 return accessibleContext; 749 } 750 751 /** 752 * This class implements accessibility support for the 753 * <code>JLayeredPane</code> class. It provides an implementation of the 754 * Java Accessibility API appropriate to layered pane user-interface 755 * elements. 756 * <p> 757 * <strong>Warning:</strong> 758 * Serialized objects of this class will not be compatible with 759 * future Swing releases. The current serialization support is 760 * appropriate for short term storage or RMI between applications running 761 * the same version of Swing. As of 1.4, support for long term storage 762 * of all JavaBeans™ 763 * has been added to the <code>java.beans</code> package. 764 * Please see {@link java.beans.XMLEncoder}. 765 */ 766 @SuppressWarnings("serial") 767 protected class AccessibleJLayeredPane extends AccessibleJComponent { 768 769 /** 770 * Get the role of this object. 771 * 772 * @return an instance of AccessibleRole describing the role of the 773 * object 774 * @see AccessibleRole 775 */ 776 public AccessibleRole getAccessibleRole() { 777 return AccessibleRole.LAYERED_PANE; 778 } 779 } 780 }