1 /*
2 * Copyright (c) 2010, 2016, 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 package javafx.scene.control;
27
28 import com.sun.javafx.scene.control.FakeFocusTextField;
29 import javafx.beans.InvalidationListener;
30 import javafx.beans.Observable;
31 import javafx.beans.WeakInvalidationListener;
32 import javafx.collections.WeakListChangeListener;
33 import javafx.scene.control.skin.ComboBoxListViewSkin;
34 import javafx.beans.property.*;
35 import javafx.beans.value.ChangeListener;
36 import javafx.beans.value.ObservableValue;
37 import javafx.collections.FXCollections;
38 import javafx.collections.ListChangeListener;
39 import javafx.collections.ObservableList;
40 import javafx.scene.AccessibleAttribute;
41 import javafx.scene.AccessibleRole;
42 import javafx.scene.Node;
43 import javafx.util.Callback;
44 import javafx.util.StringConverter;
45
46 import java.lang.ref.WeakReference;
47
48 /**
49 * An implementation of the {@link ComboBoxBase} abstract class for the most common
50 * form of ComboBox, where a popup list is shown to users providing them with
51 * a choice that they may select from. For more information around the general
52 * concepts and API of ComboBox, refer to the {@link ComboBoxBase} class
53 * documentation.
54 *
55 * <p>On top of ComboBoxBase, the ComboBox class introduces additional API. Most
56 * importantly, it adds an {@link #itemsProperty() items} property that works in
57 * much the same way as the ListView {@link ListView#itemsProperty() items}
58 * property. In other words, it is the content of the items list that is displayed
59 * to users when they click on the ComboBox button.
60 *
61 * <p>The ComboBox exposes the {@link #valueProperty()} from
62 * {@link javafx.scene.control.ComboBoxBase}, but there are some important points
63 * of the value property that need to be understood in relation to ComboBox.
64 * These include:
65 *
66 * <ol>
67 * <li>The value property <strong>is not</strong> constrained to items contained
68 * within the items list - it can be anything as long as it is a valid value
69 * of type T.</li>
70 * <li>If the value property is set to a non-null object, and subsequently the
71 * items list is cleared, the value property <strong>is not</strong> nulled out.</li>
72 * <li>Clearing the {@link javafx.scene.control.SelectionModel#clearSelection()
73 * selection} in the selection model <strong>does not</strong> null the value
74 * property - it remains the same as before.</li>
75 * <li>It is valid for the selection model to have a selection set to a given
76 * index even if there is no items in the list (or less items in the list than
77 * the given index). Once the items list is further populated, such that the
78 * list contains enough items to have an item in the given index, both the
79 * selection model {@link SelectionModel#selectedItemProperty()} and
80 * value property will be updated to have this value. This is inconsistent with
81 * other controls that use a selection model, but done intentionally for ComboBox.</li>
82 * </ol>
83 *
84 * <p>By default, when the popup list is showing, the maximum number of rows
85 * visible is 10, but this can be changed by modifying the
86 * {@link #visibleRowCountProperty() visibleRowCount} property. If the number of
87 * items in the ComboBox is less than the value of <code>visibleRowCount</code>,
88 * then the items size will be used instead so that the popup list is not
89 * exceedingly long.
90 *
91 * <p>As with ListView, it is possible to modify the
92 * {@link javafx.scene.control.SelectionModel selection model} that is used,
93 * although this is likely to be rarely changed. This is because the ComboBox
94 * enforces the need for a {@link javafx.scene.control.SingleSelectionModel}
95 * instance, and it is not likely that there is much need for alternate
96 * implementations. Nonetheless, the option is there should use cases be found
97 * for switching the selection model.
98 *
99 * <p>As the ComboBox internally renders content with a ListView, API exists in
100 * the ComboBox class to allow for a custom cell factory to be set. For more
101 * information on cell factories, refer to the {@link Cell} and {@link ListCell}
102 * classes. It is important to note that if a cell factory is set on a ComboBox,
103 * cells will only be used in the ListView that shows when the ComboBox is
104 * clicked. If you also want to customize the rendering of the 'button' area
105 * of the ComboBox, you can set a custom {@link ListCell} instance in the
106 * {@link #buttonCellProperty() button cell} property. One way of doing this
107 * is with the following code (note the use of {@code setButtonCell}:
108 *
109 * <pre>
110 * {@code
111 * Callback<ListView<String>, ListCell<String>> cellFactory = ...;
112 * ComboBox comboBox = new ComboBox();
113 * comboBox.setItems(items);
114 * comboBox.setButtonCell(cellFactory.call(null));
115 * comboBox.setCellFactory(cellFactory);}</pre>
116 *
117 * <p>Because a ComboBox can be {@link #editableProperty() editable}, and the
118 * default means of allowing user input is via a {@link TextField}, a
119 * {@link #converterProperty() string converter} property is provided to allow
120 * for developers to specify how to translate a users string into an object of
121 * type T, such that the {@link #valueProperty() value} property may contain it.
122 * By default the converter simply returns the String input as the user typed it,
123 * which therefore assumes that the type of the editable ComboBox is String. If
124 * a different type is specified and the ComboBox is to be editable, it is
125 * necessary to specify a custom {@link StringConverter}.
126 *
127 * <h3>A warning about inserting Nodes into the ComboBox items list</h3>
128 * ComboBox allows for the items list to contain elements of any type, including
129 * {@link Node} instances. Putting nodes into
130 * the items list is <strong>strongly not recommended</strong>. This is because
131 * the default {@link #cellFactoryProperty() cell factory} simply inserts Node
132 * items directly into the cell, including in the ComboBox 'button' area too.
133 * Because the scenegraph only allows for Nodes to be in one place at a time,
134 * this means that when an item is selected it becomes removed from the ComboBox
135 * list, and becomes visible in the button area. When selection changes the
136 * previously selected item returns to the list and the new selection is removed.
137 *
138 * <p>The recommended approach, rather than inserting Node instances into the
139 * items list, is to put the relevant information into the ComboBox, and then
140 * provide a custom {@link #cellFactoryProperty() cell factory}. For example,
141 * rather than use the following code:
142 *
143 * <pre>
144 * {@code
145 * ComboBox<Rectangle> cmb = new ComboBox<Rectangle>();
146 * cmb.getItems().addAll(
147 * new Rectangle(10, 10, Color.RED),
148 * new Rectangle(10, 10, Color.GREEN),
149 * new Rectangle(10, 10, Color.BLUE));}</pre>
150 *
151 * <p>You should do the following:</p>
152 *
153 * <pre><code>
154 * ComboBox<Color> cmb = new ComboBox<Color>();
155 * cmb.getItems().addAll(
156 * Color.RED,
157 * Color.GREEN,
158 * Color.BLUE);
159 *
160 * cmb.setCellFactory(new Callback<ListView<Color>, ListCell<Color>>() {
161 * @Override public ListCell<Color> call(ListView<Color> p) {
162 * return new ListCell<Color>() {
163 * private final Rectangle rectangle;
164 * {
165 * setContentDisplay(ContentDisplay.GRAPHIC_ONLY);
166 * rectangle = new Rectangle(10, 10);
167 * }
168 *
169 * @Override protected void updateItem(Color item, boolean empty) {
170 * super.updateItem(item, empty);
171 *
172 * if (item == null || empty) {
173 * setGraphic(null);
174 * } else {
175 * rectangle.setFill(item);
176 * setGraphic(rectangle);
177 * }
178 * }
179 * };
180 * }
181 *});</code></pre>
182 *
183 * <p>Admittedly the above approach is far more verbose, but it offers the
184 * required functionality without encountering the scenegraph constraints.
185 *
186 * @see ComboBoxBase
187 * @see Cell
188 * @see ListCell
189 * @see StringConverter
190 * @since JavaFX 2.1
191 */
192 public class ComboBox<T> extends ComboBoxBase<T> {
193
194 /***************************************************************************
195 * *
196 * Static properties and methods *
197 * *
198 **************************************************************************/
199
200 private static <T> StringConverter<T> defaultStringConverter() {
201 return new StringConverter<T>() {
202 @Override public String toString(T t) {
203 return t == null ? null : t.toString();
204 }
205
206 @Override public T fromString(String string) {
207 return (T) string;
208 }
209 };
210 }
211
212
213
214 /***************************************************************************
215 * *
216 * Constructors *
217 * *
218 **************************************************************************/
219
220 /**
221 * Creates a default ComboBox instance with an empty
222 * {@link #itemsProperty() items} list and default
223 * {@link #selectionModelProperty() selection model}.
224 */
225 public ComboBox() {
226 this(FXCollections.<T>observableArrayList());
227 }
228
229 /**
230 * Creates a default ComboBox instance with the provided items list and
231 * a default {@link #selectionModelProperty() selection model}.
232 */
233 public ComboBox(ObservableList<T> items) {
234 getStyleClass().add(DEFAULT_STYLE_CLASS);
235 setAccessibleRole(AccessibleRole.COMBO_BOX);
236 setItems(items);
237 setSelectionModel(new ComboBoxSelectionModel<T>(this));
238
239 // listen to the value property input by the user, and if the value is
240 // set to something that exists in the items list, we should update the
241 // selection model to indicate that this is the selected item
242 valueProperty().addListener((ov, t, t1) -> {
243 if (getItems() == null) return;
244
245 SelectionModel<T> sm = getSelectionModel();
246 int index = getItems().indexOf(t1);
247
248 if (index == -1) {
249 Runnable r = () -> {
250 sm.setSelectedIndex(-1);
251 sm.setSelectedItem(t1);
252 };
253 if (sm instanceof ComboBoxSelectionModel) {
254 ((ComboBoxSelectionModel)sm).doAtomic(r);
255 } else {
256 r.run();
257 }
258 } else {
259 // we must compare the value here with the currently selected
260 // item. If they are different, we overwrite the selection
261 // properties to reflect the new value.
262 // We do this as there can be circumstances where there are
263 // multiple instances of a value in the ComboBox items list,
264 // and if we don't check here we may change the selection
265 // mistakenly because the indexOf above will return the first
266 // instance always, and selection may be on the second or
267 // later instances. This is RT-19227.
268 T selectedItem = sm.getSelectedItem();
269 if (selectedItem == null || ! selectedItem.equals(getValue())) {
270 sm.clearAndSelect(index);
271 }
272 }
273 });
274
275 editableProperty().addListener(o -> {
276 // When we change from being editable to non-editable, we look for the
277 // current value in the items list. If it exists, we do not clear selection.
278 // When we change from being non-editable to editable, we do nothing
279 if (!isEditable()) {
280 // check if value is in items list
281 if (getItems() != null && !getItems().contains(getValue())) {
282 getSelectionModel().clearSelection();
283 }
284 }
285 });
286
287 focusedProperty().addListener(o -> {
288 if (!isFocused()) {
289 commitValue();
290 }
291 });
292 }
293
294
295
296 /***************************************************************************
297 * *
298 * Properties *
299 * *
300 **************************************************************************/
301
302 // --- items
303 /**
304 * The list of items to show within the ComboBox popup.
305 */
306 private ObjectProperty<ObservableList<T>> items = new SimpleObjectProperty<ObservableList<T>>(this, "items");
307 public final void setItems(ObservableList<T> value) { itemsProperty().set(value); }
308 public final ObservableList<T> getItems() {return items.get(); }
309 public ObjectProperty<ObservableList<T>> itemsProperty() { return items; }
310
311
312 // --- string converter
313 /**
314 * Converts the user-typed input (when the ComboBox is
315 * {@link #editableProperty() editable}) to an object of type T, such that
316 * the input may be retrieved via the {@link #valueProperty() value} property.
317 */
318 public ObjectProperty<StringConverter<T>> converterProperty() { return converter; }
319 private ObjectProperty<StringConverter<T>> converter =
320 new SimpleObjectProperty<StringConverter<T>>(this, "converter", ComboBox.<T>defaultStringConverter());
321 public final void setConverter(StringConverter<T> value) { converterProperty().set(value); }
322 public final StringConverter<T> getConverter() {return converterProperty().get(); }
323
324
325 // --- cell factory
326 /**
327 * Providing a custom cell factory allows for complete customization of the
328 * rendering of items in the ComboBox. Refer to the {@link Cell} javadoc
329 * for more information on cell factories.
330 */
331 private ObjectProperty<Callback<ListView<T>, ListCell<T>>> cellFactory =
332 new SimpleObjectProperty<Callback<ListView<T>, ListCell<T>>>(this, "cellFactory");
333 public final void setCellFactory(Callback<ListView<T>, ListCell<T>> value) { cellFactoryProperty().set(value); }
334 public final Callback<ListView<T>, ListCell<T>> getCellFactory() {return cellFactoryProperty().get(); }
335 public ObjectProperty<Callback<ListView<T>, ListCell<T>>> cellFactoryProperty() { return cellFactory; }
336
337
338 // --- button cell
339 /**
340 * The button cell is used to render what is shown in the ComboBox 'button'
341 * area. If a cell is set here, it does not change the rendering of the
342 * ComboBox popup list - that rendering is controlled via the
343 * {@link #cellFactoryProperty() cell factory} API.
344 * @since JavaFX 2.2
345 */
346 public ObjectProperty<ListCell<T>> buttonCellProperty() { return buttonCell; }
347 private ObjectProperty<ListCell<T>> buttonCell =
348 new SimpleObjectProperty<ListCell<T>>(this, "buttonCell");
349 public final void setButtonCell(ListCell<T> value) { buttonCellProperty().set(value); }
350 public final ListCell<T> getButtonCell() {return buttonCellProperty().get(); }
351
352
353 // --- Selection Model
354 /**
355 * The selection model for the ComboBox. A ComboBox only supports
356 * single selection.
357 */
358 private ObjectProperty<SingleSelectionModel<T>> selectionModel = new SimpleObjectProperty<SingleSelectionModel<T>>(this, "selectionModel") {
359 private SingleSelectionModel<T> oldSM = null;
360 @Override protected void invalidated() {
361 if (oldSM != null) {
362 oldSM.selectedItemProperty().removeListener(selectedItemListener);
363 }
364 SingleSelectionModel<T> sm = get();
365 oldSM = sm;
366 if (sm != null) {
367 sm.selectedItemProperty().addListener(selectedItemListener);
368 }
369 }
370 };
371 public final void setSelectionModel(SingleSelectionModel<T> value) { selectionModel.set(value); }
372 public final SingleSelectionModel<T> getSelectionModel() { return selectionModel.get(); }
373 public final ObjectProperty<SingleSelectionModel<T>> selectionModelProperty() { return selectionModel; }
374
375
376 // --- Visible Row Count
377 /**
378 * The maximum number of rows to be visible in the ComboBox popup when it is
379 * showing. By default this value is 10, but this can be changed to increase
380 * or decrease the height of the popup.
381 */
382 private IntegerProperty visibleRowCount
383 = new SimpleIntegerProperty(this, "visibleRowCount", 10);
384 public final void setVisibleRowCount(int value) { visibleRowCount.set(value); }
385 public final int getVisibleRowCount() { return visibleRowCount.get(); }
386 public final IntegerProperty visibleRowCountProperty() { return visibleRowCount; }
387
388
389 // --- Editor
390 private TextField textField;
391 /**
392 * The editor for the ComboBox. The editor is null if the ComboBox is not
393 * {@link #editableProperty() editable}.
394 * @since JavaFX 2.2
395 */
396 private ReadOnlyObjectWrapper<TextField> editor;
397 public final TextField getEditor() {
398 return editorProperty().get();
399 }
400 public final ReadOnlyObjectProperty<TextField> editorProperty() {
401 if (editor == null) {
402 editor = new ReadOnlyObjectWrapper<>(this, "editor");
403 textField = new FakeFocusTextField();
404 editor.set(textField);
405 }
406 return editor.getReadOnlyProperty();
407 }
408
409
410 // --- Placeholder Node
411 private ObjectProperty<Node> placeholder;
412 /**
413 * This Node is shown to the user when the ComboBox has no content to show.
414 * The placeholder node is shown in the ComboBox popup area
415 * when the items list is null or empty.
416 * @since JavaFX 8.0
417 */
418 public final ObjectProperty<Node> placeholderProperty() {
419 if (placeholder == null) {
420 placeholder = new SimpleObjectProperty<Node>(this, "placeholder");
421 }
422 return placeholder;
423 }
424 public final void setPlaceholder(Node value) {
425 placeholderProperty().set(value);
426 }
427 public final Node getPlaceholder() {
428 return placeholder == null ? null : placeholder.get();
429 }
430
431
432
433 /***************************************************************************
434 * *
435 * Methods *
436 * *
437 **************************************************************************/
438
439 /** {@inheritDoc} */
440 @Override protected Skin<?> createDefaultSkin() {
441 return new ComboBoxListViewSkin<T>(this);
442 }
443
444 /**
445 * If the ComboBox is {@link #editableProperty() editable}, calling this method will attempt to
446 * commit the current text and convert it to a {@link #valueProperty() value}.
447 * @since 9
448 */
449 public final void commitValue() {
450 if (!isEditable()) return;
451 String text = getEditor().getText();
452 StringConverter<T> converter = getConverter();
453 if (converter != null) {
454 T value = converter.fromString(text);
455 setValue(value);
456 }
457 }
458
459 /**
460 * If the ComboBox is {@link #editableProperty() editable}, calling this method will attempt to
461 * replace the editor text with the last committed {@link #valueProperty() value}.
462 * @since 9
463 */
464 public final void cancelEdit() {
465 if (!isEditable()) return;
466 final T committedValue = getValue();
467 StringConverter<T> converter = getConverter();
468 if (converter != null) {
469 String valueString = converter.toString(committedValue);
470 getEditor().setText(valueString);
471 }
472 }
473
474
475
476 /***************************************************************************
477 * *
478 * Callbacks and Events *
479 * *
480 **************************************************************************/
481
482 // Listen to changes in the selectedItem property of the SelectionModel.
483 // When it changes, set the selectedItem in the value property.
484 private ChangeListener<T> selectedItemListener = new ChangeListener<T>() {
485 @Override public void changed(ObservableValue<? extends T> ov, T t, T t1) {
486 if (wasSetAllCalled && t1 == null) {
487 // no-op: fix for RT-22572 where the developer was completely
488 // replacing all items in the ComboBox, and expecting the
489 // selection (and ComboBox.value) to remain set. If this isn't
490 // here, we would updateValue(null).
491 // Additional fix for RT-22937: adding the '&& t1 == null'.
492 // Without this, there would be circumstances where the user
493 // selecting a new value from the ComboBox would end up in here,
494 // when we really should go into the updateValue(t1) call below.
495 // We should only ever go into this clause if t1 is null.
496 } else {
497 updateValue(t1);
498 }
499
500 wasSetAllCalled = false;
501 }
502 };
503
504
505
506 /***************************************************************************
507 * *
508 * Private methods *
509 * *
510 **************************************************************************/
511
512 private void updateValue(T newValue) {
513 if (! valueProperty().isBound()) {
514 setValue(newValue);
515 }
516 }
517
518
519
520
521 /***************************************************************************
522 * *
523 * Stylesheet Handling *
524 * *
525 **************************************************************************/
526
527 private static final String DEFAULT_STYLE_CLASS = "combo-box";
528
529 private boolean wasSetAllCalled = false;
530 private int previousItemCount = -1;
531
532 // package for testing
533 static class ComboBoxSelectionModel<T> extends SingleSelectionModel<T> {
534 private final ComboBox<T> comboBox;
535
536 private boolean atomic = false;
537 private void doAtomic(Runnable r) {
538 atomic = true;
539 r.run();
540 atomic = false;
541 }
542
543 public ComboBoxSelectionModel(final ComboBox<T> cb) {
544 if (cb == null) {
545 throw new NullPointerException("ComboBox can not be null");
546 }
547 this.comboBox = cb;
548 this.comboBox.previousItemCount = getItemCount();
549
550 selectedIndexProperty().addListener(valueModel -> {
551 // we used to lazily retrieve the selected item, but now we just
552 // do it when the selection changes.
553 if (atomic) return;
554 setSelectedItem(getModelItem(getSelectedIndex()));
555 });
556
557 /*
558 * The following two listeners are used in conjunction with
559 * SelectionModel.select(T obj) to allow for a developer to select
560 * an item that is not actually in the data model. When this occurs,
561 * we actively try to find an index that matches this object, going
562 * so far as to actually watch for all changes to the items list,
563 * rechecking each time.
564 */
565 itemsObserver = new InvalidationListener() {
566 private WeakReference<ObservableList<T>> weakItemsRef = new WeakReference<>(comboBox.getItems());
567
568 @Override public void invalidated(Observable observable) {
569 ObservableList<T> oldItems = weakItemsRef.get();
570 weakItemsRef = new WeakReference<>(comboBox.getItems());
571 updateItemsObserver(oldItems, comboBox.getItems());
572 comboBox.previousItemCount = getItemCount();
573 }
574 };
575 this.comboBox.itemsProperty().addListener(new WeakInvalidationListener(itemsObserver));
576 if (comboBox.getItems() != null) {
577 this.comboBox.getItems().addListener(weakItemsContentObserver);
578 }
579 }
580
581 // watching for changes to the items list content
582 private final ListChangeListener<T> itemsContentObserver = new ListChangeListener<T>() {
583 @Override public void onChanged(Change<? extends T> c) {
584 if (comboBox.getItems() == null || comboBox.getItems().isEmpty()) {
585 setSelectedIndex(-1);
586 } else if (getSelectedIndex() == -1 && getSelectedItem() != null) {
587 int newIndex = comboBox.getItems().indexOf(getSelectedItem());
588 if (newIndex != -1) {
589 setSelectedIndex(newIndex);
590 }
591 }
592
593 int shift = 0;
594 while (c.next()) {
595 comboBox.wasSetAllCalled = comboBox.previousItemCount == c.getRemovedSize();
596
597 if (c.wasReplaced()) {
598 // no-op
599 } else if (c.wasAdded() || c.wasRemoved()) {
600 if (c.getFrom() <= getSelectedIndex() && getSelectedIndex()!= -1) {
601 shift += c.wasAdded() ? c.getAddedSize() : -c.getRemovedSize();
602 }
603 }
604 }
605
606 if (shift != 0) {
607 clearAndSelect(getSelectedIndex() + shift);
608 } else if (comboBox.wasSetAllCalled && getSelectedIndex() >= 0 && getSelectedItem() != null) {
609 // try to find the previously selected item
610 T selectedItem = getSelectedItem();
611 for (int i = 0; i < comboBox.getItems().size(); i++) {
612 if (selectedItem.equals(comboBox.getItems().get(i))) {
613 comboBox.setValue(null);
614 setSelectedItem(null);
615 setSelectedIndex(i);
616 break;
617 }
618 }
619 }
620
621 comboBox.previousItemCount = getItemCount();
622 }
623 };
624
625 // watching for changes to the items list
626 private final InvalidationListener itemsObserver;
627
628 private WeakListChangeListener<T> weakItemsContentObserver =
629 new WeakListChangeListener<T>(itemsContentObserver);
630
631
632 private void updateItemsObserver(ObservableList<T> oldList, ObservableList<T> newList) {
633 // update listeners
634 if (oldList != null) {
635 oldList.removeListener(weakItemsContentObserver);
636 }
637 if (newList != null) {
638 newList.addListener(weakItemsContentObserver);
639 }
640
641 // when the items list totally changes, we should clear out
642 // the selection and focus
643 int newValueIndex = -1;
644 if (newList != null) {
645 T value = comboBox.getValue();
646 if (value != null) {
647 newValueIndex = newList.indexOf(value);
648 }
649 }
650 setSelectedIndex(newValueIndex);
651 }
652
653 // API Implementation
654 @Override protected T getModelItem(int index) {
655 final ObservableList<T> items = comboBox.getItems();
656 if (items == null) return null;
657 if (index < 0 || index >= items.size()) return null;
658 return items.get(index);
659 }
660
661 @Override protected int getItemCount() {
662 final ObservableList<T> items = comboBox.getItems();
663 return items == null ? 0 : items.size();
664 }
665 }
666
667 /***************************************************************************
668 * *
669 * Accessibility handling *
670 * *
671 **************************************************************************/
672
673 @Override
674 public Object queryAccessibleAttribute(AccessibleAttribute attribute, Object... parameters) {
675 switch(attribute) {
676 case TEXT:
677 String accText = getAccessibleText();
678 if (accText != null && !accText.isEmpty()) return accText;
679
680 //let the skin first.
681 Object title = super.queryAccessibleAttribute(attribute, parameters);
682 if (title != null) return title;
683 StringConverter<T> converter = getConverter();
684 if (converter == null) {
685 return getValue() != null ? getValue().toString() : "";
686 }
687 return converter.toString(getValue());
688 default: return super.queryAccessibleAttribute(attribute, parameters);
689 }
690 }
691
692 }