JavaFX docs指出WebView is ready when Worker.State.SUCCEEDED is reached，除非您稍等片刻（即WebView，Worker.State.SUCCEEDED，Animation等），否则将呈现空白页。
这表明在WebView内部发生了一个事件，准备将其捕获，但这是什么？
有Transition，但其中大多数似乎与PauseTransition无关，是交互式的（人类遮住了种族条件）或使用了任意的Transitions（从100ms到2,000ms的任何位置。）>
我尝试过：
从over 7,000 code snippets on GitHub which use SwingFXUtils.fromFXImage的尺寸内监听SwingFXUtils.fromFXImage（高度和宽度属性WebView实现了changed(...)，可以监视这些东西）]
盲目告诉FX应用程序线程上的changed(...)所有信息。
将DOM侦听器/触发器或JavaScript侦听器/触发器添加到WebView
DoubleProperty时，JavaScript和DOM似乎都已正确加载。 DOM / JavaScript侦听器似乎无济于事。使用ObservableValue或runLater(...)有效地“休眠”而不阻塞主FX线程。
runLater(...)，而且设计不好。对于高性能或关键任务应用程序，这迫使程序员在速度或可靠性之间做出权衡，这两者对于用户而言都是潜在的不良体验。什么时候打电话给WebView？
用法：
SUCCEEDED代码段：
Animation相关：
TransitionWebView.snapshot(...)SnapshotRaceCondition.initialize();
BufferedImage bufferedImage = SnapshotRaceCondition.capture("<html style='background-color: red;'><h1>TEST</h1></html>");
/**
* Notes:
* - The color is to observe the otherwise non-obvious cropping that occurs
* with some techniques, such as `setPrefWidth`, `autosize`, etc.
* - Call this function in a loop and then display/write `BufferedImage` to
* to see strange behavior on subsequent calls.
* - Recommended, modify `<h1>TEST</h1` with a counter to see content from
* previous captures render much later.
*/
import javafx.application.Application;
import javafx.application.Platform;
import javafx.beans.value.ChangeListener;
import javafx.beans.value.ObservableValue;
import javafx.concurrent.Worker;
import javafx.embed.swing.SwingFXUtils;
import javafx.scene.Scene;
import javafx.scene.SnapshotParameters;
import javafx.scene.image.WritableImage;
import javafx.scene.web.WebView;
import javafx.stage.Stage;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.atomic.AtomicReference;
import java.util.logging.Logger;
public class SnapshotRaceCondition extends Application {
private static final Logger log = Logger.getLogger(SnapshotRaceCondition.class.getName());
// self reference
private static SnapshotRaceCondition instance = null;
// concurrent-safe containers for flags/exceptions/image data
private static AtomicBoolean started = new AtomicBoolean(false);
private static AtomicBoolean finished = new AtomicBoolean(true);
private static AtomicReference<Throwable> thrown = new AtomicReference<>(null);
private static AtomicReference<BufferedImage> capture = new AtomicReference<>(null);
// main javafx objects
private static WebView webView = null;
private static Stage stage = null;
// frequency for checking fx is started
private static final int STARTUP_TIMEOUT= 10; // seconds
private static final int STARTUP_SLEEP_INTERVAL = 250; // millis
// frequency for checking capture has occured
private static final int CAPTURE_SLEEP_INTERVAL = 10; // millis
/** Called by JavaFX thread */
public SnapshotRaceCondition() {
instance = this;
}
/** Starts JavaFX thread if not already running */
public static synchronized void initialize() throws IOException {
if (instance == null) {
new Thread(() -> Application.launch(SnapshotRaceCondition.class)).start();
}
for(int i = 0; i < (STARTUP_TIMEOUT * 1000); i += STARTUP_SLEEP_INTERVAL) {
if (started.get()) { break; }
log.fine("Waiting for JavaFX...");
try { Thread.sleep(STARTUP_SLEEP_INTERVAL); } catch(Exception ignore) {}
}
if (!started.get()) {
throw new IOException("JavaFX did not start");
}
}
@Override
public void start(Stage primaryStage) {
started.set(true);
log.fine("Started JavaFX, creating WebView...");
stage = primaryStage;
primaryStage.setScene(new Scene(webView = new WebView()));
// Add listener for SUCCEEDED
Worker<Void> worker = webView.getEngine().getLoadWorker();
worker.stateProperty().addListener(stateListener);
// Prevents JavaFX from shutting down when hiding window, useful for calling capture(...) in succession
Platform.setImplicitExit(false);
}
/** Listens for a SUCCEEDED state to activate image capture **/
private static ChangeListener<Worker.State> stateListener = (ov, oldState, newState) -> {
if (newState == Worker.State.SUCCEEDED) {
WritableImage snapshot = webView.snapshot(new SnapshotParameters(), null);
capture.set(SwingFXUtils.fromFXImage(snapshot, null));
finished.set(true);
stage.hide();
}
};
/** Listen for failures **/
private static ChangeListener<Throwable> exceptListener = new ChangeListener<Throwable>() {
@Override
public void changed(ObservableValue<? extends Throwable> obs, Throwable oldExc, Throwable newExc) {
if (newExc != null) { thrown.set(newExc); }
}
};
/** Loads the specified HTML, triggering stateListener above **/
public static synchronized BufferedImage capture(final String html) throws Throwable {
capture.set(null);
thrown.set(null);
finished.set(false);
// run these actions on the JavaFX thread
Platform.runLater(new Thread(() -> {
try {
webView.getEngine().loadContent(html, "text/html");
stage.show(); // JDK-8087569: will not capture without showing stage
stage.toBack();
}
catch(Throwable t) {
thrown.set(t);
}
}));
// wait for capture to complete by monitoring our own finished flag
while(!finished.get() && thrown.get() == null) {
log.fine("Waiting on capture...");
try {
Thread.sleep(CAPTURE_SLEEP_INTERVAL);
}
catch(InterruptedException e) {
log.warning(e.getLocalizedMessage());
}
}
if (thrown.get() != null) {
throw thrown.get();
}
return capture.get();
}
}
JavaFX文档指出，当到达Worker.State.SUCCEEDED时，WebView就绪，除非您等待一会儿（即，Animation，Transition，PauseTransition等），否则将呈现空白页面。 ...
我之前没有见过的建议是监听JavaFX脉冲以确定是否绘制了JavaFX:how to resize the stage when using webview。
似乎是使用WebEngine的WebView方法时发生的错误。使用com.sun加载本地文件时也会发生这种情况，但是在这种情况下，调用PauseTransition将对此进行补偿。