Question

My application is Swing-based. I would like to introduce JavaFX and configure it to render a Scene on a secondary display.
I could use a JFrame to hold a JFXPanel which could hold a JFXPanel but I would like to achieve this with JavaFX API.

Subclassing com.sun.glass.ui.Application and using Application.launch(this) is not an option because the invoking thread would be blocked.

When instantiating a Stage from Swing EDT, the error I get is:

java.lang.IllegalStateException: Toolkit not initialized

Any pointers?

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EDIT: Conclusions

Problem: Non-trivial Swing GUI application needs to run JavaFX components. Application’s startup process initializes the GUI after starting up a dependent service layer.

Solutions

Subclass JavaFX Application class and run it in a separate thread e.g.:

public class JavaFXInitializer extends Application {
    @Override
    public void start(Stage stage) throws Exception {
        // JavaFX should be initialized
        someGlobalVar.setInitialized(true);
    }
}

Sidenote: Because Application.launch() method takes a Class<? extends Application> as an argument, one has to use a global variable to signal JavaFX environment has been initialized.

Alternative approach: instantiate JFXPanel in Swing Event Dispatcher Thread:

final CountDownLatch latch = new CountDownLatch(1);
SwingUtilities.invokeLater(new Runnable() {
    public void run() {
        new JFXPanel(); // initializes JavaFX environment
        latch.countDown();
    }
});
latch.await();

By using this approach the calling thread will wait until JavaFX environment is set up.

Pick any solution you see fit. I went with the second one because it doesn’t need a global variable to signal the initialization of JavaFX environment and also doesn’t waste a thread.

Answer 1

Found a solution. If I just create a JFXPanel from Swing EDT before invoking JavaFX Platform.runLater it works.
I don’t know how reliable this solution is, I might choose JFXPanel and JFrame if turns out to be unstable.

public class BootJavaFX {

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                new JFXPanel(); // this will prepare JavaFX toolkit and environment
                Platform.runLater(new Runnable() {
                    @Override
                    public void run() {
                        StageBuilder.create()
                                .scene(SceneBuilder.create()
                                        .width(320)
                                        .height(240)
                                        .root(LabelBuilder.create()
                                                .font(Font.font("Arial", 54))
                                                .text("JavaFX")
                                                .build())
                                        .build())
                                .onCloseRequest(new EventHandler<WindowEvent>() {
                                    @Override
                                    public void handle(WindowEvent windowEvent) {
                                        System.exit(0);
                                    }
                                })
                                .build()
                                .show();
                    }
                });
            }
        });
    }
}