正確管理JavaFX中的線程

Question

我正在嘗試調用外部命令並在製作時在TextArea中輸出其輸出。我閱讀了關於JavaFX併發性的文檔，我相信我做了我必須做的工作。

我使用Task類運行我的工作：

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); 
} 

不過，我發現了以下異常：

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簡直是Button。我不正確的是什麼？從文檔，使用Task這種方式應該是足夠的...

Answer 1

愚蠢的我。我想保證沒有人能夠運行命令（並在文本區域輸出），而另一個命令已經運行，因此​​和Thread.join。但是，這是錯誤的。我也誤解了Task類的文檔。

這裏有兩個錯誤我已經作出，以及如何解決這些問題：

• Thread.join塊的FX應用程序線程直到任務結束了，所以沒有什麼是永遠顯示在文本區域。我用Semaphore替換了這個同步。信號量阻止第二個線程輸入run方法，並在後臺線程終止時使用Task偵聽器方法釋放。 FX應用程序線程立即退出該方法。

• Task.call根據文檔，實際上不能與任何JavaFX組件進行交互。只有聽衆方法（cancelled,succeeded,failed）纔可以這樣做。因此，我將撥打setActive和setInactive的電話提取到call方法的外部。

的代碼演示這些變化如下：

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

如果我得到它的權利，stacktrace只是說，代碼中有一些其他行在FX應用程序線程之外操縱一些UI控件 - 這一定不會發生。

應用程序代碼的第一線下來的痕跡（不JDK代碼）是： 在com.dici.javafx.components.ExternalCommandRunner.setState(ExternalCommandRunner.java:66)

這似乎是foowloing在你的榜樣行：

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

如果站僅有按鈕和方法setState（）操作它，並從您自己的自定義線程中調用，那麼恰好發生了框架抱怨的事情。

嘗試將任何東西操作FX應用程序線程上的UI控件，正如您在handleLog方法中使用Platform.runLater(() -> { ... })一樣。