How do you embed a Swing JPanel into a JavaFX frame?

From Integrating JavaFX 2.0 with Swing and SWT there is a code that allows you to embed a JFXPanel inside a Swing JFrame. I was wondering is there a reverse of that where a JPanel is embedded inside an Application or Stage which is the equivalent of JFrame as noted in Converting from Swing to JavaFX?

/**
 * Simple class demonstrating interoperability between Swing and JavaFX. This
 * class is adapted from the example provided in the Javadoc documentation for
 * {@code javafx.embed.swing.JFXPanel}.
 */
public class SwingJavaFxInteroperabilityDemo
{
   private static void initAndShowGUI()
   {
      // This method is invoked on Swing thread
      final JFrame frame = new JFrame("JavaFX / Swing Integrated");
      final JFXPanel fxPanel = new JFXPanel();
      frame.add(fxPanel);
      frame.setVisible(true);

      Platform.runLater(new Runnable()
      {
         @Override
         public void run()
         {
            initFX(fxPanel);
         }
      });
   }

   private static void initFX(JFXPanel fxPanel)
   {
      // This method is invoked on JavaFX thread
      final Scene scene = TextIntegrationSceneCreator.createTextScene();
      fxPanel.setScene(scene);
   }

   public static void main(String[] arguments)
   {
      SwingUtilities.invokeLater(new Runnable()
      {
         @Override
         public void run()
         {
            initAndShowGUI();
         }
      });
   }   
}

You can use a SwingNode to place swing content into a JavaFX node.

Sample Application

There is an example application in the SwingNode documentation previously linked:

import javafx.application.Application;
import javafx.embed.swing.SwingNode;
import javafx.scene.Scene;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;

import javax.swing.*;

public class SwingFx extends Application {

    @Override
    public void start(Stage stage) {
        final SwingNode swingNode = new SwingNode();
        createAndSetSwingContent(swingNode);

        StackPane pane = new StackPane();
        pane.getChildren().add(swingNode);

        stage.setScene(new Scene(pane, 100, 50));
        stage.show();
    }

    private void createAndSetSwingContent(
        final SwingNode swingNode
    ) {
        SwingUtilities.invokeLater(() -> 
                swingNode.setContent(
                        new JButton("Click me!")
                )
        );
    }

    public static void main(String[] args) {
        launch(args);
    }
}

Dependency and Module Management

If you are using Maven or Gradle for your JavaFX dependencies, you can import the library for JavaFX/Swing integration using:

<dependency>
    <groupId>org.openjfx</groupId>
    <artifactId>javafx-swing</artifactId>
    <version>16</version>
</dependency>

If you are writing a modular application using Jigsaw capabilities, placing the following in your module-info.java file will make the JavaFX swing integration module visible to your application:

requires javafx.swing;

Embedding Swing in JavaFX Tutorial

Oracle provides a good tutorial for embedding Swing content in JavaFX:

• Embedding Swing Content in JavaFX Applications.

The tutorial is written for Java 8 but is still relevant. The tutorial covers topics such as thread management and event handling, and I advise anybody attempting the integration of JavaFX and Swing to understand those topics very well before attempting integration, otherwise bad and unpredictable things may occur.

In general, I advise not mixing JavaFX and Swing code unless that is absolutely necessary for your application.

Canvas Integration and Heavyweight Swing Components

Note, from the SwingNode documentation:

The hierarchy of components contained in the JComponent instance should not contain any heavyweight components, otherwise, SwingNode may fail to paint it.

An example of a heavyweight component is a Canvas. If you wish to use an awt canvas in JavaFX, see:

• Interoperability between Graphics2D and GraphicsContext

Specifically, consider using the FXGraphics2D library:

FXGraphics2D is an implementation of Java2D’s Graphics2D API that targets a JavaFX canvas.