java.lang.IllegalStateException: Not on FX application thread

本文讨论了在JavaFX应用中遇到'Not on FX application thread'异常的原因和解决方案。当尝试在非FX线程中更新界面组件时,会抛出此异常。解决方法是使用`Platform.runLater()`方法确保所有界面更新操作都在FX应用线程中执行。
  • 问题描述

运行javaFX程序,系统会自动创建一个FX application thread线程,用于更新界面的组件信息,例如ListViewitemsLabeltext。当我们想运用多线程实现业务,而自己创建的线程又直接导致了界面组件信息的更新时,控制台就会抛出java.lang.IllegalStateException异常。

完整异常栈如下
Exception in thread “pool-2-thread-1” java.lang.IllegalStateException: Not on FX application thread; currentThread = pool-2-thread-1
at com.sun.javafx.tk.Toolkit.checkFxUserThread(Toolkit.java:279)
at com.sun.javafx.tk.quantum.QuantumToolkit.checkFxUserThread(QuantumToolkit.java:423)
at javafx.scene.Parent2.onProposedChange(Parent.java:367)atcom.sun.javafx.collections.VetoableListDecorator.setAll(VetoableListDecorator.java:113)atcom.sun.javafx.collections.VetoableListDecorator.setAll(VetoableListDecorator.java:108)atcom.sun.javafx.scene.control.skin.LabeledSkinBase.updateChildren(LabeledSkinBase.java:575)atcom.sun.javafx.scene.control.skin.LabeledSkinBase.handleControlPropertyChanged(LabeledSkinBase.java:204)atcom.sun.javafx.scene.control.skin.LabelSkin.handleControlPropertyChanged(LabelSkin.java:49)atcom.sun.javafx.scene.control.skin.BehaviorSkinBase.lambda2.onProposedChange(Parent.java:367) at com.sun.javafx.collections.VetoableListDecorator.setAll(VetoableListDecorator.java:113) at com.sun.javafx.collections.VetoableListDecorator.setAll(VetoableListDecorator.java:108) at com.sun.javafx.scene.control.skin.LabeledSkinBase.updateChildren(LabeledSkinBase.java:575) at com.sun.javafx.scene.control.skin.LabeledSkinBase.handleControlPropertyChanged(LabeledSkinBase.java:204) at com.sun.javafx.scene.control.skin.LabelSkin.handleControlPropertyChanged(LabelSkin.java:49) at com.sun.javafx.scene.control.skin.BehaviorSkinBase.lambda2.onProposedChange(Parent.java:367)atcom.sun.javafx.collections.VetoableListDecorator.setAll(VetoableListDecorator.java:113)atcom.sun.javafx.collections.VetoableListDecorator.setAll(VetoableListDecorator.java:108)atcom.sun.javafx.scene.control.skin.LabeledSkinBase.updateChildren(LabeledSkinBase.java:575)atcom.sun.javafx.scene.control.skin.LabeledSkinBase.handleControlPropertyChanged(LabeledSkinBase.java:204)atcom.sun.javafx.scene.control.skin.LabelSkin.handleControlPropertyChanged(LabelSkin.java:49)atcom.sun.javafx.scene.control.skin.BehaviorSkinBase.lambdaregisterChangeListener$61(BehaviorSkinBase.java:197)
at com.sun.javafx.scene.control.MultiplePropertyChangeListenerHandler1.changed(MultiplePropertyChangeListenerHandler.java:55)atjavafx.beans.value.WeakChangeListener.changed(WeakChangeListener.java:89)atcom.sun.javafx.binding.ExpressionHelper1.changed(MultiplePropertyChangeListenerHandler.java:55) at javafx.beans.value.WeakChangeListener.changed(WeakChangeListener.java:89) at com.sun.javafx.binding.ExpressionHelper1.changed(MultiplePropertyChangeListenerHandler.java:55)atjavafx.beans.value.WeakChangeListener.changed(WeakChangeListener.java:89)atcom.sun.javafx.binding.ExpressionHelperSingleChange.fireValueChangedEvent(ExpressionHelper.java:182)
at com.sun.javafx.binding.ExpressionHelper.fireValueChangedEvent(ExpressionHelper.java:81)
at javafx.beans.property.StringPropertyBase.fireValueChangedEvent(StringPropertyBase.java:103)
at javafx.beans.property.StringPropertyBase.markInvalid(StringPropertyBase.java:110)
at javafx.beans.property.StringPropertyBase.set(StringPropertyBase.java:144)
at javafx.beans.property.StringPropertyBase.set(StringPropertyBase.java:49)
at javafx.beans.property.StringProperty.setValue(StringProperty.java:65)
at javafx.scene.control.Labeled.setText(Labeled.java:145)
at controller.RootLayoutController.updateLabel(RootLayoutController.java:255)
at controller.RootLayoutController.getReady(RootLayoutController.java:238)
at controller.RootLayoutController.lambda$login2(RootLayoutController.java:221)atjava.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)atjava.util.concurrent.ThreadPoolExecutor2(RootLayoutController.java:221) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) at java.util.concurrent.ThreadPoolExecutor2(RootLayoutController.java:221)atjava.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)atjava.util.concurrent.ThreadPoolExecutorWorker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)


  • 解决方案

之所以抛出异常,是因为javaFX程序不允许用户在FX application thread线程外更新界面的组件信息,换句话说,所有的更新界面组件的信息的代码,都应该在在FX application thread线程中执行。解决办法还是有的,用Platform类的runLater方法可以解决该问题。

runLater方法的定义如下
public static void runLater(Runnable runnable) {
  PlatformImpl.runLater(runnable);
}

通过阅读javaAPI文档,可以知晓,该方法可以将参数runnable将要执行的代码,交给FX application thread线程执行,这样问题就解决了。具体解决模板如下。

  • 假设在一个自己创建的线程中,调用了update()方法,update()方法用于更新主界面的组件信息,这会导致如题的异常
  • 此时,可以如下调用update()方法
    Platform.runLater(()->{
      update();
       //任何更新界面组件信息的代码
    });
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