Question

使用org.controlsfx.control.RangeSlider时，我收到了NullPointerException。这是一个简单的代码示例：

package experimental_main;

import org.controlsfx.control.RangeSlider;

import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.layout.BorderPane;
import javafx.stage.Stage;


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


    @Override
    public void start(Stage primaryStage) throws Exception
    {
        Button button = new Button("Click me");
        RangeSlider rangeSlider = new RangeSlider(0, 10, 2, 4);

        BorderPane borderPane = new BorderPane();
        borderPane.setCenter(rangeSlider);
        borderPane.setTop(button);

        Scene scene = new Scene(borderPane, 300, 300);
        primaryStage.setScene(scene);
        primaryStage.show();
    }
}

当RangeSlider的右拇指聚焦时按Tab键或在左拇指聚焦时按Shift + Tab键会发生异常。这些按键会导致RangeSlider无法按预期失去焦点，但此操作也会导致NullPointerException。这是异常的堆栈跟踪：

Exception in thread "JavaFX Application Thread" java.lang.NullPointerException
at com.sun.javafx.scene.traversal.TraversalEngine.select(Unknown Source)
at impl.org.controlsfx.skin.RangeSliderSkin$5.handle(RangeSliderSkin.java:150)
at impl.org.controlsfx.skin.RangeSliderSkin$5.handle(RangeSliderSkin.java:132)
at com.sun.javafx.event.CompositeEventHandler$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.EventUtil.fireEventImpl(Unknown Source)
at com.sun.javafx.event.EventUtil.fireEvent(Unknown Source)
at javafx.event.Event.fireEvent(Unknown Source)
at javafx.scene.Scene$KeyHandler.process(Unknown Source)
at javafx.scene.Scene$KeyHandler.access$1800(Unknown Source)
at javafx.scene.Scene.impl_processKeyEvent(Unknown Source)
at javafx.scene.Scene$ScenePeerListener.keyEvent(Unknown Source)
at com.sun.javafx.tk.quantum.GlassViewEventHandler$KeyEventNotification.run(Unknown Source)
at com.sun.javafx.tk.quantum.GlassViewEventHandler$KeyEventNotification.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleKeyEvent$353(Unknown Source)
at com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(Unknown Source)
at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleKeyEvent(Unknown Source)
at com.sun.glass.ui.View.handleKeyEvent(Unknown Source)
at com.sun.glass.ui.View.notifyKey(Unknown Source)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.lambda$null$148(Unknown Source)
at java.lang.Thread.run(Unknown Source)

按Tab键（或Shift + Tab键）以使RangeSlider的拇指聚焦时，没有异常。

我做错了什么或者它是个错误？是否有RangeSlider类实现的替代方法？

Answer 1

RangeSliderSkin的这个监听器似乎会导致NPE：

 EventHandler<KeyEvent> keyEventHandler = new EventHandler<KeyEvent>() {
            @Override public void handle(KeyEvent event) {
                if (KeyCode.TAB.equals(event.getCode())) {
                    if (lowThumb.isFocused()) {
                        if (event.isShiftDown()) {
                            lowThumb.setFocus(false);
                            new ParentTraversalEngine(rangeSlider).select(rangeSlider, Direction.PREVIOUS);
                        } else {
                            lowThumb.setFocus(false);
                            highThumb.setFocus(true);
                        }
                        event.consume();
                    } else if (highThumb.isFocused()) {
                        if(event.isShiftDown()) {
                            highThumb.setFocus(false);
                            lowThumb.setFocus(true);
                        } else {
                            highThumb.setFocus(false);
                            new ParentTraversalEngine(rangeSlider).select(rangeSlider, Direction.NEXT);
                        }
                        event.consume();
                    }
                }
            }
        };

更具体地说，行new ParentTraversalEngine(rangeSlider).select(rangeSlider, Direction.NEXT); ParentTraversalEngine在没有Algorithm参数的情况下被初始化，因此调用select(rangeSlider, Direction.NEXT)会导致NPE，因为它应该是：

抛出： java.lang.NullPointerException - 如果没有算法

javadoc

Answer 2

从版本8.40.13开始修复错误。

在焦点滑块上按Tab键时，RangeSlider会导致NullPointerException

2 个答案: