java - 正确管理 JavaFX 中的线程

Question

我正在尝试调用外部命令并在生成时在 TextArea 中打印其输出。我阅读了有关 JavaFX 并发性的文档，并且我相信我已经做了我必须做的事情来使其工作。

我正在使用 Task 类来运行我的作业:

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); 
}

但是，我遇到以下异常:

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 只是一个按钮。我哪里做的不对？从文档来看，使用 Task 这种方式应该足够了......

Answer 1

如果我猜对了，堆栈跟踪只是表明代码中还有另一行，其中某些 UI 控件是从 FX 应用程序线程外部进行操作的 - 而这种情况一定不会发生。

应用程序代码的第一行(不是 JDK 代码)是: 在com.dici.javafx.components.ExternalCommandRunner.setState(ExternalCommandRunner.java:66)

在您的示例中，这似乎是以下几行:

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

如果 stop 只是一个按钮，并且方法 setState() 操纵它并从您自己的自定义线程调用，那么就会发生框架所提示的情况。

尝试将操作 UI 控件的任何内容放在 FX 应用程序线程上，就像您在 Platform.runLater(() -> { ... }) 中所做的那样handleLog 方法。