Javafx WebEngine:背景工作者到底发生了什么? UI挂起在loadContent(大HTML文档)

来自
WebEngine文档:

Loading always happens on a background thread. Methods that initiate
loading return immediately after scheduling a background job. To track
progress and/or cancel a job, use the Worker instance available from
the getLoadWorker() method.

我有一个HTML string,我通过WebEngine.loadContent(String)加载到WebView上.这个字符串大约有500万个字符.在Platform.runLater()中运行它(我必须在JavaFX线程中运行它,否则我得到一个错误)我的UI挂起大约一分钟.

如果我不在Platform.runLater()中运行它,我得到:

java.lang.IllegalStateException: Not on FX application thread; currentThread = populator
    at com.sun.javafx.tk.Toolkit.checkFxUserThread(Toolkit.java:236)
    at com.sun.javafx.tk.quantum.QuantumToolkit.checkFxUserThread(QuantumToolkit.java:423)
    at javafx.scene.web.WebEngine.checkThread(WebEngine.java:1216)
    at javafx.scene.web.WebEngine.loadContent(WebEngine.java:931)
    at javafx.scene.web.WebEngine.loadContent(WebEngine.java:919)
    ...

我不能通过webEngine.getLoadWorker().getProgress()查询webEngine,也不能通过webEngine.getLoadWorker()取消取消.因为我必须再次在挂起的JavaFX线程上运行它…

所以我必须等到页面加载,然后先前提交的任何Platform.runLater(() – > webEngine.getLoadWorker().getProgress())(在网页加载过程中)将运行,每次给我1.0. ..

我用来查询Worker的代码:

// WebView
wvIn.getEngine().getLoadWorker().stateProperty().addListener(new ChangeListener<Worker.State>() {
    class ProgressThread extends Thread {
        private Worker.State loadWorkerState;

        synchronized Worker.State getLoadWorkerState() {
            return loadWorkerState;
        }

        synchronized void setLoadWorkerState(Worker.State loadWorkerState) {
            this.loadWorkerState = loadWorkerState;
        }

        {
            setDaemon(true);
            setName("LoadingWebpageProgressThread");
        }

        public void run() {
            while (true) {
                try {
                    if (getLoadWorkerState() == Worker.State.RUNNING)
                        // piWv ProgressIndicator (WebView loading)
                        Platform.runLater(() -> piWv.setVisible(true));
                    while (getLoadWorkerState() == Worker.State.RUNNING) {
                        Platform.runLater(() -> {
                            piWv.setProgress(wvIn.getEngine().getLoadWorker().getProgress());
                            // TODO delete
                            System.out.println(wvIn.getEngine().getLoadWorker().getProgress());
                        });
                        Thread.sleep(100);
                    }
                    if (getLoadWorkerState() == Worker.State.SUCCEEDED) {
                        Platform.runLater(() -> piWv.setProgress(1d));
                        Thread.sleep(100);
                        Platform.runLater(() -> {
                            piWv.setVisible(false);
                            piWv.setProgress(0d);
                        });
                    }
                    synchronized (this) {
                        wait();
                    }
                } catch (InterruptedException e) {
                }
            }
        }
    };

    final ProgressThread progressThread = new ProgressThread();
    {
        progressThread.start();
    }

    // executed on JavaFX Thread
    @Override
    public void changed(ObservableValue<? extends State> observable, State oldValue, State newValue) {
        if (newValue == State.SUCCEEDED) {
            JSObject window = (JSObject) wvIn.getEngine().executeScript("window");
            window.setMember("controller", mainController);
            progressThread.setLoadWorkerState(newValue);
            progressThread.interrupt();
        } else if (newValue == State.RUNNING) {
            progressThread.setLoadWorkerState(newValue);
            progressThread.interrupt();
        }
        // TODO delete
        System.out.println(oldValue + "->" + newValue);
    }
});

反正是否强制加载后台线程?

JavaFX线程到底发生了什么?它是填充WebView的过程吗?

最佳答案 您在问题中显示的HTML文件几乎立即加载到我的计算机上.

在我看来,问题在于你的代码.嗯,这很麻烦.请允许我指出它看起来不太好,因为它容易出现deadlock,并使用例外来实现guarded-blocks的形式.

看起来你并不完全理解events的概念.
除非为了简洁起见以某种方式切断了问题中的代码片段,否则ProgressThread实例完全没用.
您已经根据需要调度了ChangeListener个事件,并在JavaFX Application Thread上执行回调;只是使用它.

indicator.setVisible(false); // Start hidden
engine.getLoadWorker().progressProperty().addListener((observable, oldValue, newValue) -> {
    indicator.setProgress(newValue.doubleValue());
    indicator.setVisible(indicator.getProgress() != 1D);
});

或者,您可以使用binding的强大功能:

Worker<Void> worker = engine.getLoadWorker();
indicator.visibleProperty().bind(worker.stateProperty().isEqualTo(Worker.State.RUNNING));
indicator.progressProperty().bind(worker.progressProperty());

对于您的JavaScript代码,我建议您收听文档事件而不是工作状态事件:它们在您的情况下更有意义,并且在页面实际完成渲染时触发它们,而不仅仅是在页面数据完成下载时.

engine.documentProperty().addListener((observable, oldValue, newValue) -> {
    if (newValue == null) {
        return;
    }
    JSObject window = (JSObject)engine.executeScript("window");
    window.setMember("controller", mainController);
});

请注意,在我的机器上,加载过程中进度始终为零.我认为问题在于你的HTML代码:如果你试图加载一些其他资源,比如你现在正在阅读的网页,进度指示器将提供更愉快的体验,在页面内容完成之前多次更新加载.

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