how to switch between two stylesheets in javafx.

To switch between two stylesheets in JavaFX, you can use the setUserAgentStylesheet method of the Application class to set the stylesheet for the application.

Here's an example of how you can do this:

import javafx.application.Application;
import javafx.stage.Stage;

public class Main extends Application {
    @Override
    public void start(Stage primaryStage) {
        // Set the first stylesheet
        Application.setUserAgentStylesheet(STYLESHEET_MODENA);

        // ...

        // Set the second stylesheet
        Application.setUserAgentStylesheet(STYLESHEET_CASPIAN);
    }
}

This code will set the first stylesheet when the application starts, and then switch to the second stylesheet at a later point.

Note that the setUserAgentStylesheet method only affects the styles of the JavaFX components, and does not affect the styles of HTML content displayed in a WebView. To switch between stylesheets for HTML content, you can use JavaScript to manipulate the link elements in the HTML document.

Here's an example of how you can do this:

WebView webView = new WebView();
WebEngine webEngine = webView.getEngine();

// Switch to the first stylesheet
webEngine.executeScript("document.getElementById('stylesheet1').disabled = false;");
webEngine.executeScript("document.getElementById('stylesheet2').disabled = true;");

// ...

// Switch to the second stylesheet
webEngine.executeScript("document.getElementById('stylesheet1').disabled = true;");
webEngine.executeScript("document.getElementById('stylesheet2').disabled = false;");

This code will disable the first stylesheet and enable the second stylesheet when switching to the second stylesheet.

Note that the executeScript method requires the ScriptEngine module to be enabled in your application. You can enable the ScriptEngine module by adding the following line to your module-info.java file:

requires javafx.web;