正确管理JavaFX中的线程

Question

我正在尝试调用外部命令并在制作时在TextArea中输出其输出。我阅读了关于JavaFX并发性的文档，我相信我做了我必须做的工作。

我使用Task类运行我的工作：

public synchronized void run(ProcessBuilder processBuilder) throws IOException, InterruptedException { 
    ExternalCommandRunner self = this; 
    Thread taskThread = new Thread(new Task<Void>() { 
     @Override 
     public Void call() throws Exception { 
      setActive(); 
      try { 
       runningProcess = processBuilder.start(); 

       StreamPrinter inputStream = new StreamPrinter(runningProcess.getInputStream(), self::handleLog); 
       StreamPrinter errorStream = new StreamPrinter(runningProcess.getErrorStream(), self::handleLog); 
       outputTextArea.clear(); 

       new Thread(inputStream).start(); 
       new Thread(errorStream).start(); 
       runningProcess.waitFor(); 
       return null; 
      } finally { 
       stop.fire(); 
       setInactive(); 
      } 
     } 
    }); 
    taskThread.setDaemon(true); 
    taskThread.start(); 
    taskThread.join(); 
} 

private void handleLog (String line) { Platform.runLater(() -> outputTextArea.appendText(line + "\n")); } 
private void setActive ()   { setState(STOP_ACTIVE_ICON , false)       ; } 
private void setInactive()   { setState(STOP_INACTIVE_ICON, true)        ; } 
private void setState (String iconPath, boolean disableButton) { 
    stop.setGraphic(imageViewFromResource(iconPath, Resources.class)); 
    stop.setDisable(disableButton); 
} 

不过，我发现了以下异常：

Exception in thread "Thread-5" java.lang.IllegalStateException: Not on FX application thread; currentThread = Thread-5 
    at com.sun.javafx.tk.Toolkit.checkFxUserThread(Unknown Source) 
    at com.sun.javafx.tk.quantum.QuantumToolkit.checkFxUserThread(Unknown Source) 
    at javafx.scene.Parent$2.onProposedChange(Unknown Source) 
    at com.sun.javafx.collections.VetoableListDecorator.setAll(Unknown Source) 
    at com.sun.javafx.collections.VetoableListDecorator.setAll(Unknown Source) 
    at com.sun.javafx.scene.control.skin.LabeledSkinBase.updateChildren(Unknown Source) 
    at com.sun.javafx.scene.control.skin.LabeledSkinBase.handleControlPropertyChanged(Unknown Source) 
    at com.sun.javafx.scene.control.skin.ButtonSkin.handleControlPropertyChanged(Unknown Source) 
    at com.sun.javafx.scene.control.skin.BehaviorSkinBase.lambda$registerChangeListener$61(Unknown Source) 
    at com.sun.javafx.scene.control.MultiplePropertyChangeListenerHandler$1.changed(Unknown Source) 
    at javafx.beans.value.WeakChangeListener.changed(Unknown Source) 
    at com.sun.javafx.binding.ExpressionHelper$SingleChange.fireValueChangedEvent(Unknown Source) 
    at com.sun.javafx.binding.ExpressionHelper.fireValueChangedEvent(Unknown Source) 
    at javafx.beans.property.ObjectPropertyBase.fireValueChangedEvent(Unknown Source) 
    at javafx.beans.property.ObjectPropertyBase.markInvalid(Unknown Source) 
    at javafx.beans.property.ObjectPropertyBase.set(Unknown Source) 
    at javafx.css.StyleableObjectProperty.set(Unknown Source) 
    at javafx.beans.property.ObjectProperty.setValue(Unknown Source) 
    at javafx.scene.control.Labeled.setGraphic(Unknown Source) 
    at com.dici.javafx.components.ExternalCommandRunner.setState(ExternalCommandRunner.java:66) 
    at com.dici.javafx.components.ExternalCommandRunner.setActive(ExternalCommandRunner.java:63) 
    at com.dici.javafx.components.ExternalCommandRunner.access$000(ExternalCommandRunner.java:19) 
    at com.dici.javafx.components.ExternalCommandRunner$1.call(ExternalCommandRunner.java:39) 
    at com.dici.javafx.components.ExternalCommandRunner$1.call(ExternalCommandRunner.java:36) 
    at javafx.concurrent.Task$TaskCallable.call(Unknown Source) 
    at java.util.concurrent.FutureTask.run(Unknown Source) 
    at java.lang.Thread.run(Unknown Source) 

stop简直是Button。我不正确的是什么？从文档，使用Task这种方式应该是足够的...

Answer 1

愚蠢的我。我想保证没有人能够运行命令（并在文本区域输出），而另一个命令已经运行，因此​​和Thread.join。但是，这是错误的。我也误解了Task类的文档。

这里有两个错误我已经作出，以及如何解决这些问题：

• Thread.join块的FX应用程序线程直到任务结束了，所以没有什么是永远显示在文本区域。我用Semaphore替换了这个同步。信号量阻止第二个线程输入run方法，并在后台线程终止时使用Task侦听器方法释放。 FX应用程序线程立即退出该方法。

• Task.call根据文档，实际上不能与任何JavaFX组件进行交互。只有听众方法（cancelled,succeeded,failed）才可以这样做。因此，我将拨打setActive和setInactive的电话提取到call方法的外部。

的代码演示这些变化如下：

private final Semaphore runMutex = new Semaphore(1); 

public void run(ProcessBuilder processBuilder) throws IOException, InterruptedException { 
    runMutex.acquire(); 
    setActive(); 
    ExternalCommandRunner self = this; 
    Thread taskThread = new Thread(new Task<Void>() { 
     @Override 
     public Void call() throws Exception { 
      runningProcess = processBuilder.start(); 

      StreamPrinter inputStream = new StreamPrinter(runningProcess.getInputStream(), self::handleLog); 
      StreamPrinter errorStream = new StreamPrinter(runningProcess.getErrorStream(), self::handleLog); 
      outputTextArea.clear(); 

      new Thread(inputStream).start(); 
      new Thread(errorStream).start(); 
      runningProcess.waitFor(); 
      return null; 
     } 

     @Override protected void cancelled() { super.cancelled(); terminate(); } 
     @Override protected void failed () { super.failed (); terminate(); } 
     @Override protected void succeeded() { super.succeeded(); terminate(); } 

     private void terminate() { 
      stop.fire(); 
      setInactive(); 
      runMutex.release(); 
     } 
    }); 
    taskThread.setDaemon(true); 
    taskThread.start(); 
} 

Answer 2

如果我得到它的权利，stacktrace只是说，代码中有一些其他行在FX应用程序线程之外操纵一些UI控件 - 这一定不会发生。

应用程序代码的第一线下来的痕迹（不JDK代码）是： 在com.dici.javafx.components.ExternalCommandRunner.setState(ExternalCommandRunner.java:66)

这似乎是foowloing在你的榜样行：

stop.setGraphic(imageViewFromResource(iconPath, Resources.class)); 
stop.setDisable(disableButton); 

如果站仅有按钮和方法setState（）操作它，并从您自己的自定义线程中调用，那么恰好发生了框架抱怨的事情。

尝试将任何东西操作FX应用程序线程上的UI控件，正如您在handleLog方法中使用Platform.runLater(() -> { ... })一样。