JavaFX Spinner 空文本 nullpointerexception

Question

我有一个问题，如果清除编辑器文本并提交，然后单击递增或递减按钮，可编辑的 JavaFX 8 Spinner会导致未捕获的NullPointerException 。 这是 j8u60 j8u77。 运气好的话，递增/递减按钮会卡在按下状态，并且 NPE 会不断锁定应用程序。

以下代码为我重现了该问题：

import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.Spinner;
import javafx.scene.control.SpinnerValueFactory;
import javafx.scene.control.SpinnerValueFactory.IntegerSpinnerValueFactory;
import javafx.stage.Stage;

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

    @Override
    public void start(Stage aPrimaryStage) throws Exception {
        IntegerSpinnerValueFactory valueFactory = new IntegerSpinnerValueFactory(0, 10);
        Spinner<Integer> spinner = new Spinner<>(valueFactory);
        spinner.setEditable(true);
        aPrimaryStage.setScene(new Scene(spinner));
        aPrimaryStage.show();
    }
}

运行它，清除文本，按回车（ NullPointerException ），单击增量或减量按钮现在也会导致 NPE。

任何人都可以确认这是一个 JavaFX 错误并提出解决方法吗？

编辑：异常堆栈跟踪

Exception in thread "JavaFX Application Thread" java.lang.NullPointerException
    at javafx.scene.control.SpinnerValueFactory$IntegerSpinnerValueFactory.lambda$new$215(SpinnerValueFactory.java:475)
    at com.sun.javafx.binding.ExpressionHelper$Generic.fireValueChangedEvent(ExpressionHelper.java:361)
    at com.sun.javafx.binding.ExpressionHelper.fireValueChangedEvent(ExpressionHelper.java:81)
    at javafx.beans.property.ObjectPropertyBase.fireValueChangedEvent(ObjectPropertyBase.java:105)
    at javafx.beans.property.ObjectPropertyBase.markInvalid(ObjectPropertyBase.java:112)
    at javafx.beans.property.ObjectPropertyBase.set(ObjectPropertyBase.java:146)
    at javafx.scene.control.SpinnerValueFactory.setValue(SpinnerValueFactory.java:150)
    at javafx.scene.control.Spinner.lambda$new$210(Spinner.java:139)
    at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:86)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
    at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
    at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:49)
    at javafx.event.Event.fireEvent(Event.java:198)
    at javafx.scene.Node.fireEvent(Node.java:8411)
    at com.sun.javafx.scene.control.behavior.TextFieldBehavior.fire(TextFieldBehavior.java:179)
    at com.sun.javafx.scene.control.behavior.TextInputControlBehavior.callAction(TextInputControlBehavior.java:178)
    at com.sun.javafx.scene.control.behavior.BehaviorBase.callActionForEvent(BehaviorBase.java:218)
    at com.sun.javafx.scene.control.behavior.TextInputControlBehavior.callActionForEvent(TextInputControlBehavior.java:127)
    at com.sun.javafx.scene.control.behavior.BehaviorBase.lambda$new$74(BehaviorBase.java:135)
    at com.sun.javafx.event.CompositeEventHandler$NormalEventHandlerRecord.handleBubblingEvent(CompositeEventHandler.java:218)
    at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:80)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
    at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
    at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:49)
    at javafx.event.Event.fireEvent(Event.java:198)
    at javafx.scene.Node.fireEvent(Node.java:8411)
    at com.sun.javafx.scene.control.skin.SpinnerSkin.lambda$new$473(SpinnerSkin.java:151)
    at com.sun.javafx.event.CompositeEventHandler$NormalEventFilterRecord.handleCapturingEvent(CompositeEventHandler.java:282)
    at com.sun.javafx.event.CompositeEventHandler.dispatchCapturingEvent(CompositeEventHandler.java:98)
    at com.sun.javafx.event.EventHandlerManager.dispatchCapturingEvent(EventHandlerManager.java:223)
    at com.sun.javafx.event.EventHandlerManager.dispatchCapturingEvent(EventHandlerManager.java:180)
    at com.sun.javafx.event.CompositeEventDispatcher.dispatchCapturingEvent(CompositeEventDispatcher.java:43)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:52)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
    at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:54)
    at javafx.event.Event.fireEvent(Event.java:198)
    at javafx.scene.Scene$KeyHandler.process(Scene.java:3964)
    at javafx.scene.Scene$KeyHandler.access$1800(Scene.java:3910)
    at javafx.scene.Scene.impl_processKeyEvent(Scene.java:2040)
    at javafx.scene.Scene$ScenePeerListener.keyEvent(Scene.java:2501)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler$KeyEventNotification.run(GlassViewEventHandler.java:197)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler$KeyEventNotification.run(GlassViewEventHandler.java:147)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleKeyEvent$353(GlassViewEventHandler.java:228)
    at com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:389)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleKeyEvent(GlassViewEventHandler.java:227)
    at com.sun.glass.ui.View.handleKeyEvent(View.java:546)
    at com.sun.glass.ui.View.notifyKey(View.java:966)
    at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at com.sun.glass.ui.win.WinApplication.lambda$null$148(WinApplication.java:191)
    at java.lang.Thread.run(Thread.java:745)

Answer 1

这是基于Integer的Spinner控件的正确和预期行为。

如果您不希望用户编辑通过Factory设置的值，则应将其Editable属性设置为false。

或者您应该处理由微调器的value属性引发的事件。

以下是如何执行此操作的简单示例：

import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.Spinner;
import javafx.scene.control.SpinnerValueFactory;
import javafx.scene.control.SpinnerValueFactory.IntegerSpinnerValueFactory;
import javafx.stage.Stage;

import javafx.beans.value.ChangeListener;
import javafx.beans.value.ObservableValue;

public class Spin extends Application {
    Spinner<Integer> spinner;

    public static void main(String[] args) {
        launch(args);
    }

    @Override
    public void start(Stage aPrimaryStage) throws Exception {
        IntegerSpinnerValueFactory valueFactory = new IntegerSpinnerValueFactory(0, 10);
        spinner = new Spinner<>(valueFactory);
        spinner.setEditable(true);
        spinner.valueProperty().addListener((observableValue, oldValue, newValue) -> handleSpin(observableValue, oldValue, newValue));

        aPrimaryStage.setScene(new Scene(spinner));
        aPrimaryStage.show();
    }

    private void handleSpin(ObservableValue<?> observableValue, Number oldValue, Number newValue) {
        try {
            if (newValue == null) {
                spinner.getValueFactory().setValue((int)oldValue);
            }
        } catch (Exception e) {
            System.out.println(e.getMessage());
        }
    }
}

如果您希望使用转换器类来帮助更全面地处理更改， 这也可以帮助您。

另请参阅有关setEditable方法的官方文档;

Answer 2

我通过JDK源进行了翻找。

NPE是从if (newValue < getMin()) {在监听器lambda中抛出的：

javafx.scene.control.SpinnerValueFactory.java

    public IntegerSpinnerValueFactory(@NamedArg("min") int min,
                                      @NamedArg("max") int max,
                                      @NamedArg("initialValue") int initialValue,
                                      @NamedArg("amountToStepBy") int amountToStepBy) {
        setMin(min);
        setMax(max);
        setAmountToStepBy(amountToStepBy);
        setConverter(new IntegerStringConverter());

        valueProperty().addListener((o, oldValue, newValue) -> {
            // when the value is set, we need to react to ensure it is a
            // valid value (and if not, blow up appropriately)
            if (newValue < getMin()) { 
                setValue(getMin());
            } else if (newValue > getMax()) {
                setValue(getMax());
            }
        });
        setValue(initialValue >= min && initialValue <= max ? initialValue : min);
    }

想必newValue是null和自动拆箱null ，抛出NPE。 由于输入来自编辑器，我怀疑IntegerStringConverter是默认转换器。

看看这里的实现：

javafx.util.converter.IntegerStringConverter

public class IntegerStringConverter extends StringConverter<Integer> {
    /** {@inheritDoc} */
    @Override public Integer fromString(String value) {
        // If the specified value is null or zero-length, return null
        if (value == null) {
            return null;
        }

        value = value.trim();

        if (value.length() < 1) {
            return null;
        }

        return Integer.valueOf(value);
    }

    /** {@inheritDoc} */
    @Override public String toString(Integer value) {
        // If the specified value is null, return a zero-length String
        if (value == null) {
            return "";
        }

        return (Integer.toString(((Integer)value).intValue()));
    }
}

我们看到它将为空字符串高兴地返回null ，这是合理的，因为输入没有有效值。

跟踪调用堆栈我发现值的来源：

javafx.scene.control.Spinner

public Spinner() {
    getStyleClass().add(DEFAULT_STYLE_CLASS);
    setAccessibleRole(AccessibleRole.SPINNER);

    getEditor().setOnAction(action -> {
        String text = getEditor().getText();
        SpinnerValueFactory<T> valueFactory = getValueFactory();
        if (valueFactory != null) {
            StringConverter<T> converter = valueFactory.getConverter();
            if (converter != null) {
                T value = converter.fromString(text);
                valueFactory.setValue(value);
            }
        }
    });

使用从转换器T value = converter.fromString(text);获得的值设置该值T value = converter.fromString(text); 大概是空的。 此时我认为spinner类应检查该value是否为null以及是否将以前的值恢复到编辑器。

我现在相当确定这是一个错误。 此外，我不认为使用永远不会返回null的转换器的工作将会正常工作，因为它只会掩盖问题，并且当值无法转换时应该返回什么值？

编辑：解决方法

使用“返回有效”策略替换微调器编辑器的onAction以拒绝无效输入可修复此问题：

public static <T> void fixSpinner2(Spinner<T> aSpinner) {
    aSpinner.getEditor().setOnAction(action -> {
        String text = aSpinner.getEditor().getText();
        SpinnerValueFactory<T> factory = aSpinner.getValueFactory();
        if (factory != null) {
            StringConverter<T> converter = factory.getConverter();
            if (converter != null) {
                T value = converter.fromString(text);
                if (null != value) {
                    factory.setValue(value);
                }
                else {
                    aSpinner.getEditor().setText(converter.toString(factory.getValue()));
                }
            }
        }
        action.consume();
    });
}

与valueProperty上的侦听器相反，这避免了使用无效数据触发其他侦听器。 然而，这突出了微调器类中的另一个问题。 虽然上面通过按Enter键返回有效值来解决问题。 擦除输入而不提交（按Enter键）然后按递增或递减将导致相同的NPE，但调用堆栈略有不同。

原因：

public void increment(int steps) {
    SpinnerValueFactory<T> valueFactory = getValueFactory();
    if (valueFactory == null) {
        throw new IllegalStateException("Can't increment Spinner with a null SpinnerValueFactory");
    }
    commitEditorText();
    valueFactory.increment(steps);
}

递减类似，都调用下面的commitEditorText ：

private void commitEditorText() {
    if (!isEditable()) return;
    String text = getEditor().getText();
    SpinnerValueFactory<T> valueFactory = getValueFactory();
    if (valueFactory != null) {
        StringConverter<T> converter = valueFactory.getConverter();
        if (converter != null) {
            T value = converter.fromString(text);
            valueFactory.setValue(value);
        }
    }
}

注意构造函数中onAction的复制粘贴：

    getEditor().setOnAction(action -> {
        String text = getEditor().getText();
        SpinnerValueFactory<T> valueFactory = getValueFactory();
        if (valueFactory != null) {
            StringConverter<T> converter = valueFactory.getConverter();
            if (converter != null) {
                T value = converter.fromString(text);
                valueFactory.setValue(value);
            }
        }
    });

我相信应该更改commitEditorText以在编辑器上触发onAction ，如下所示：

private void commitEditorText() {
    if (!isEditable()) return;
    getEditor().getOnAction().handle(new ActionEvent(this, this));
}

然后行为将是一致的，并让编辑器有机会在输入到值工厂之前处理输入。

Answer 3

我认为这是一个错误： IntegerSpinnerValueFactory应该正确处理这种情况。

一种解决方法是为微调器值工厂提供converter器，如果文本值无效，则将其converter为默认值：

import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.Spinner;
import javafx.scene.control.SpinnerValueFactory.IntegerSpinnerValueFactory;
import javafx.stage.Stage;
import javafx.util.StringConverter;

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

    @Override
    public void start(Stage aPrimaryStage) throws Exception {
        IntegerSpinnerValueFactory valueFactory = new IntegerSpinnerValueFactory(0, 10);

        valueFactory.setConverter(new StringConverter<Integer>() {

            @Override
            public String toString(Integer object) {
                return object.toString() ;
            }

            @Override
            public Integer fromString(String string) {
                if (string.matches("-?\\d+")) {
                    return new Integer(string);
                }
                // default to 0:
                return 0 ;
            }

        });

        Spinner<Integer> spinner = new Spinner<>(valueFactory);
        spinner.setEditable(true);
        aPrimaryStage.setScene(new Scene(spinner));
        aPrimaryStage.show();
    }
}

Answer 4

这是一个已知的错误，已在Java 9中修复 - 请参阅https://bugs.openjdk.java.net/browse/JDK-8150962

Answer 5

另一个对我有用的答案，阻止你输入任何非数字值：

spinnerIndex.editorProperty().getValue().textProperty().addListener(new ChangeListener<String>() {

    private static boolean isInteger(final String s) {
        try {
            @SuppressWarnings("unused")
            int d = Integer.parseInt(s);
            return true;
        }
        catch (NumberFormatException e) {
            return false;
        }
    }

    @Override
    public void changed(ObservableValue<? extends String> observable, String oldValue, String newValue) {
        if (!isInteger(newValue)) {
            final StringProperty sp = (StringProperty)observable;
            sp.set(oldValue);
        }
    }
});