Java FX: java.lang.IllegalStateException: Not on FX application thread

Java FX: java.lang.IllegalStateException: Not on FX application thread

• 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ListView的items、Label的text。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.onProposedChang**e(Paren**t.jav**a:367)atcom.sun.javaf**x.collections.VetoableListDecorator.setAl**l(VetoableListDecorator.jav**a:113)atcom.sun.javaf**x.collections.VetoableListDecorator.setAl**l(VetoableListDecorator.jav**a:108)atcom.sun.javaf**x.scene.control.ski**n.LabeledSkinBase.updateChildre**n(LabeledSkinBase.jav**a:575)atcom.sun.javaf**x.scene.control.ski**n.LabeledSkinBase.handleControlPropertyChange**d(LabeledSkinBase.jav**a:204)atcom.sun.javaf**x.scene.control.ski**n.LabelSkin.handleControlPropertyChange**d(LabelSkin.jav**a:49)atcom.sun.javaf**x.scene.control.ski**n.BehaviorSkinBas**e.lambd**aregisterChangeListener$61(BehaviorSkinBase.java:197)
at com.sun.javafx.scene.control.MultiplePropertyChangeListenerHandler1.changed(MultiplePropertyChangeListenerHandler.java:55)atjavafx.beans.value.WeakChangeListener.changed(WeakChangeListener.java:89)atcom.sun.javafx.binding.ExpressionHelper1.changed(MultiplePropertyChangeListenerHandler.java:55) at javafx.beans.value.WeakChangeListener.changed(WeakChangeListener.java:89) at com.sun.javafx.binding.ExpressionHelper1.changed(MultiplePropertyChangeListenerHandler.jav**a:55)atjavaf**x.beans.value.WeakChangeListene**r.changed(WeakChangeListene**r.jav**a:89)atcom.sun.javaf**x.binding.ExpressionHelpe**rSingleChange.fireValueChangedEvent(ExpressionHelper.java:182)
at com.sun.javafx.binding.ExpressionHelper.fireValueChangedEvent(ExpressionHelper.java:81)
at javafx.beans.property.StringPropertyBase.fireValueChangedEvent(StringPropertyBase.java:103)
at javafx.beans.property.StringPropertyBase.markInvalid(StringPropertyBase.java:110)
at javafx.beans.property.StringPropertyBase.set(StringPropertyBase.java:144)
at javafx.beans.property.StringPropertyBase.set(StringPropertyBase.java:49)
at javafx.beans.property.StringProperty.setValue(StringProperty.java:65)
at javafx.scene.control.Labeled.setText(Labeled.java:145)
at controller.RootLayoutController.updateLabel(RootLayoutController.java:255)
at controller.RootLayoutController.getReady(RootLayoutController.java:238)
at controller.RootLayoutController.lambda$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(RootLayoutControlle**r.jav**a:221)atjav**a.uti**l.concurren**t.ThreadPoolExecuto**r.runWorker(ThreadPoolExecuto**r.jav**a:1149)atjav**a.uti**l.concurren**t.ThreadPoolExecuto**rWorker.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
});