Cannot call JavaFX from WebView JavaScript on Windows (VirtualBox)

问题

The following code works on Linux, but the callback does not work on Windows (VirtualBox VM). Can you please tell me why?

Java:

    public class WebViewTest extends Application {
      private Label label = new Label ("...");
      public static void main (String[] args) {
        launch (args);
      }
      @Override
      public void start (Stage stage) throws Exception {
        WebView webView = new WebView ();
        WebEngine webEngine = webView.getEngine ();
        webEngine.setJavaScriptEnabled (true);
        JSObject window = (JSObject) webView.getEngine ().executeScript ("window");
        window.setMember ("java", new Callback ());
        webEngine.load (getClass ().getResource ("WebViewTest.html").toString ());
        BorderPane pane = new BorderPane ();
        pane.setCenter (webView);
        pane.setBottom (label);
        Scene scene = new Scene (pane);
        stage.setScene (scene);
        stage.show ();
      }
      public class Callback {
        public void click () {
        label.setText ("Clicked :-)");
      }
    }
  }

HTML:

<!DOCTYPE html>
<html>
  <head>
    <title>Test</title>
    <meta charset="UTF-8">
  </head>
  <body>
    <button onclick="window.java.click ();">Test</button>
  </body>
</html>

回答1:

The trick was to create the Callback as a class field:

private Callback callback = new Callback ();

And then:

webEngine.load (getClass ().getResource ("WebViewTest.html").toString ());
JSObject window = (JSObject) webView.getEngine ().executeScript ("window");
// BUG // window.setMember ("java", new Callback ());
window.setMember ("java", callback);

Maybe there is some abusive garbage collecting on Windows? I don't know...

回答2:

The window object is likely replaced when a new DOM is loaded into the web engine. Try setting the callback when the document is loaded:

Callback callback = new Callback();
webEngine.documentProperty().addListener((obs, oldDoc, newDoc) -> {
    if (newDoc != null) {
        JSObject window = (JSObject) webView.getEngine ().executeScript ("window");
        window.setMember ("java", callback);                
    }
});

(You can see that the window object changes by System.out.println(System.identityHashCode(webView.getEngine ().executeScript ("window")) before loading the HTML, and System.out.println(System.identityHashCode(window)) in the document listener.)

回答3:

I had a similar problem and after digging deep, I found out that you are supposed to call window.setMember ("java", new Callback ()); after rendering your html so this should work:

JSObject window = (JSObject) webView.getEngine ().executeScript ("window");
webEngine.load (getClass ().getResource ("WebViewTest.html").toString ())
window.setMember ("java", new Callback ());

Also note that if you perform a reload or if you navigate to another page, you will lose your functionality again. A solid solution will be:

webEngine.documentProperty().addListener(((observable, oldValue, newValue) -> {
   if (Objects.nonNull(newValue)) {
        JSObject window = (JSObject) webEngine.executeScript("window");
        window.setMember("engine", callback);
    }
}));

来源：https://stackoverflow.com/questions/41537474/cannot-call-javafx-from-webview-javascript-on-windows-virtualbox

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