Question

我想包含对我的组合框的检查以限制对某些值的“访问”。我可以从列表中删除那些无法访问的项目，是的，但是我希望用户看到其他选项，即使他还不能选择它们。

问题：在changelistener中选择另一个值会导致IndexOutOfBoundsException，我不明白为什么。

这是一个SSCCE。它创建一个具有整数值的ComboBox，默认情况下会选择第一个。然后我试着保持它很简单：每次更改值都被视为“错误”，我将选择更改回第一个元素。但仍然是，IndexOutOfBounds：

import javafx.application.Application;
import javafx.collections.FXCollections;
import javafx.collections.ObservableList;
import javafx.scene.Group;
import javafx.scene.Scene;
import javafx.scene.control.ComboBox;
import javafx.stage.Stage;

public class Tester extends Application{
    public static void main(String[] args) {
        launch(args);
    }

    @Override
    public void start(Stage stage) throws Exception {
        ComboBox<Integer> box = new ComboBox<Integer>();
        ObservableList<Integer> vals= FXCollections.observableArrayList(0,1,2,3);

        box.setItems(vals);
        box.getSelectionModel().select(0);
        /*box.valueProperty().addListener((observable, oldValue, newValue) -> {
            box.getSelectionModel().select(0);
        });*/
        /*box.getSelectionModel().selectedItemProperty().addListener((observable,oldValue,newValue)->{
            System.out.println(oldValue+","+newValue);
            box.getSelectionModel().select(0);
        });*/

        box.getSelectionModel().selectedIndexProperty().addListener((observable,oldValue,newValue)->{
            System.out.println(oldValue+","+newValue);
            box.getSelectionModel().select(0);
        });
        Scene scene = new Scene(new Group(box),500,500);
        stage.setScene(scene);
        stage.show();
    }
}

我用valueProperty，selectedItemProperty和selectedIndexProperty测试了它，以及所有这些：

box.getSelectionModel().select(0);

box.getSelectionModel().selectFirst();

box.getSelectionModel().selectPrevious();

box.setValue(0);

if (oldValue.intValue() < newValue.intValue())
            box.getSelectionModel().select(oldValue.intValue());

唯一有效的想法是设定价值本身：

box.getSelectionModel().select(box.getSelectionModel().getSelectedIndex());
box.setValue(box.getValue));

以下是例外：

Exception in thread "JavaFX Application Thread" java.lang.IndexOutOfBoundsException
    at com.sun.javafx.scene.control.ReadOnlyUnbackedObservableList.subList(Unknown Source)
    at javafx.collections.ListChangeListener$Change.getAddedSubList(Unknown Source)
    at com.sun.javafx.scene.control.behavior.ListViewBehavior.lambda$new$178(Unknown Source)
    at com.sun.javafx.scene.control.behavior.ListViewBehavior$$Lambda$126/644961012.onChanged(Unknown Source)
    at javafx.collections.WeakListChangeListener.onChanged(Unknown Source)
    at com.sun.javafx.collections.ListListenerHelper$Generic.fireValueChangedEvent(Unknown Source)
    at com.sun.javafx.collections.ListListenerHelper.fireValueChangedEvent(Unknown Source)
    at com.sun.javafx.scene.control.ReadOnlyUnbackedObservableList.callObservers(Unknown Source)
    at javafx.scene.control.MultipleSelectionModelBase.clearAndSelect(Unknown Source)
    at javafx.scene.control.ListView$ListViewBitSetSelectionModel.clearAndSelect(Unknown Source)
    at com.sun.javafx.scene.control.behavior.CellBehaviorBase.simpleSelect(Unknown Source)
    at com.sun.javafx.scene.control.behavior.CellBehaviorBase.doSelect(Unknown Source)
    at com.sun.javafx.scene.control.behavior.CellBehaviorBase.mousePressed(Unknown Source)
    at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(Unknown Source)
    at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(Unknown Source)
    at com.sun.javafx.event.CompositeEventHandler$NormalEventHandlerRecord.handleBubblingEvent(Unknown Source)
    at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(Unknown Source)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(Unknown Source)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(Unknown Source)
    at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(Unknown Source)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(Unknown Source)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(Unknown Source)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(Unknown Source)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(Unknown Source)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(Unknown Source)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(Unknown Source)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(Unknown Source)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(Unknown Source)
    at com.sun.javafx.event.EventUtil.fireEventImpl(Unknown Source)
    at com.sun.javafx.event.EventUtil.fireEvent(Unknown Source)
    at javafx.event.Event.fireEvent(Unknown Source)
    at javafx.scene.Scene$MouseHandler.process(Unknown Source)
    at javafx.scene.Scene$MouseHandler.access$1500(Unknown Source)
    at javafx.scene.Scene.impl_processMouseEvent(Unknown Source)
    at javafx.scene.Scene$ScenePeerListener.mouseEvent(Unknown Source)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(Unknown Source)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleMouseEvent$350(Unknown Source)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler$$Lambda$172/2037973250.get(Unknown Source)
    at com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(Unknown Source)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(Unknown Source)
    at com.sun.glass.ui.View.handleMouseEvent(Unknown Source)
    at com.sun.glass.ui.View.notifyMouse(Unknown Source)
    at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at com.sun.glass.ui.win.WinApplication.lambda$null$145(Unknown Source)
    at com.sun.glass.ui.win.WinApplication$$Lambda$36/2117255219.run(Unknown Source)
    at java.lang.Thread.run(Unknown Source)

我做错了什么？

Answer 1

在JavaFX中，当更改已在进行中时，您无法更改ObservableList的内容。这里发生的事情是你的听众（你试过的任何一个）在box.getSelctionModel().getSelectedItems() ObservableList改变的一部分被解雇。所以基本上，在处理选择更改时，您无法更改选择。

无论如何，你的解决方案有点笨拙。如果您在所选项目（或组合框值）上有另一个侦听器，即使您的方法有效，它也会暂时看到组合框中包含＆＃34;非法＆＃34;选择。例如，在上面的示例中，如果用户尝试选择＆＃34; 1＆＃34;，则另一个听众会看到选择更改为不允许的值＆＃34; 1＆＃34;，然后返回＆＃34; 0＆＃ 34 ;.处理此监听器中不应允许的值可能会使您的程序逻辑变得非常复杂。

更好的方法imho是阻止用户选择不允许的值。您可以使用设置单元格的disable属性的单元工厂来执行此操作：

    box.setCellFactory(lv -> new ListCell<Integer>() {
        @Override
        public void updateItem(Integer item, boolean empty) {
            super.updateItem(item, empty);
            if (empty) {
                setText(null);
            } else {
                setText(item.toString());
                setDisable(item.intValue() != 0);
            }
        }
    });

在外部样式表中包含以下内容将为用户提供通常的视觉提示：项目无法选择：

.combo-box-popup .list-cell:disabled  {
    -fx-opacity: 0.4 ;
}

Answer 2

我知道线程很老但我有类似的问题而且我以不同的方式解决了问题。我试图改变ComboBox＆＃39;当该项目在该时刻不可用时（例如由于给定条件），在其onAction方法中选择了项目。正如@James_D在他的回答中所说，问题是设置当前正在修改的对象。

只需在Platform.runLater()方法中添加您的代码：

Platform.runLater(() -> box.getSelectionModel().select(0));

就我而言，它起作用了，希望它也能在其他人中发挥作用。

JavaFX ComboBox更改值导致IndexOutOfBoundsException

2 个答案: