问题描述
所以我遵循了本教程: https://www.youtube.com/watch?v= gyyj57O0FVI
So I followed this tutorial: https://www.youtube.com/watch?v=gyyj57O0FVI
,我在javafx8中编写了完全相同的代码.
and I made exactly the same code in javafx8.
public class CountdownController implements Initializable{
@FXML
private Label labTime;
@Override
public void initialize(URL location, ResourceBundle resources) {
new Thread(){
public void run(){
while(true){
Calendar calendar = new GregorianCalendar();
int hour = calendar.get(Calendar.HOUR);
int minute = calendar.get(Calendar.MINUTE);
int second = calendar.get(Calendar.SECOND);
String time = hour + ":" + minute + ":" + second;
labTime.setText(time);
}
}
}.start();
}
关闭窗口后,应用程序/线程仍在系统中运行.我的猜测是因为无限循环,但是线程不应该在应用程序关闭时终止吗?
After I close the Window, application/thread is still running in the system. My guess its because the infinite loop, but shouldnt the thread be terminated with application closing?
第二件事是,当我尝试为Label设置文本时,出现错误:
Second thing is that when I try to set the text for Label I get the error:
Exception in thread "Thread-4" java.lang.IllegalStateException: Not on FX application thread; currentThread = Thread-4
at com.sun.javafx.tk.Toolkit.checkFxUserThread(Toolkit.java:204)
at com.sun.javafx.tk.quantum.QuantumToolkit.checkFxUserThread(QuantumToolkit.java:364)
at javafx.scene.Parent$2.onProposedChange(Parent.java:364)
at com.sun.javafx.collections.VetoableListDecorator.setAll(VetoableListDecorator.java:113)
at com.sun.javafx.collections.VetoableListDecorator.setAll(VetoableListDecorator.java:108)
at com.sun.javafx.scene.control.skin.LabeledSkinBase.updateChildren(LabeledSkinBase.java:575)
at com.sun.javafx.scene.control.skin.LabeledSkinBase.handleControlPropertyChanged(LabeledSkinBase.java:204)
at com.sun.javafx.scene.control.skin.LabelSkin.handleControlPropertyChanged(LabelSkin.java:49)
at com.sun.javafx.scene.control.skin.BehaviorSkinBase.lambda$registerChangeListener$60(BehaviorSkinBase.java:197)
at com.sun.javafx.scene.control.skin.BehaviorSkinBase$$Lambda$144/1099655841.call(Unknown Source)
at com.sun.javafx.scene.control.MultiplePropertyChangeListenerHandler$1.changed(MultiplePropertyChangeListenerHandler.java:55)
at javafx.beans.value.WeakChangeListener.changed(WeakChangeListener.java:89)
at com.sun.javafx.binding.ExpressionHelper$SingleChange.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:143)
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:146)
at application.CountdownController$1.run(CountdownController.java:29)
...是的,我将阅读有关线程的更多信息,但我想知道这些问题的答案.
...yes, I am going to read more about threads, but I would like to know the answer to these questions.
推荐答案
第一部分
一个线程在创建时独立于其他线程运行.您有一个具有无限循环的新线程,这意味着即使关闭阶段,该线程也将永远运行.
Part I
A thread, when created, runs independent of other threads. You have a new thread which has an infinite loop, which implies, it will keep running forever, even after the stage has been closed.
通常不建议使用无限循环,因为要打破该循环非常困难.
Normally, using a infinite loop is not advised, because breaking out of it is very difficult.
建议您使用:
- TimerTask
- ScheduledExecutorService
然后您可以呼叫其中一个(根据您使用的是什么)
You can then call either one of them (based on whatever you are using)
- TimerTask.cancel()
- ScheduledExecutorService.shutdownNow()
舞台关闭时.您可以使用类似:
when your stage is closed. You can use something like :
stage.setOnCloseRequest(closeEvent -> {
timertask.cancel();
});
JavaFX API的 (感谢James_D评论的)
这些不需要显式取消,因为ScheduledService
使用守护程序线程,而AnimationTimer
在JavaFX线程上运行.
These do not need to be explicitly canceled as ScheduledService
uses daemon threads and AnimationTimer
runs on the JavaFX thread.
- ScheduledService
- AnimationTimer
问题的第二部分已在论坛中一次又一次地得到回答.
Your second part of the question has been answered time and again in the forum.
由于创建了新线程并尝试更新label
(它是一个JavaFX节点),因此它将引发异常.有关更多信息,请访问:
Since you have created a new thread and trying to update label
, which is a JavaFX node, it throws the exception. For more information, please visit:
为什么会收到java.lang.IllegalStateException不在FX应用程序线程上"在JavaFX上?
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