JavaFX getScene() returns null in initialize method of the controller

Question

I built a small application in JavaFX yesterday. I wanted to get the Scene of the application in the Controller class. I got an error every time I tried to get the scene in

Answer 1

You can do

private Node replaceSceneContent(String fxml) throws Exception {
    FXMLLoader loader = new FXMLLoader();
    loader.setBuilderFactory(new JavaFXBuilderFactory());
    loader.setLocation(Main.class.getResource(fxml));

    BorderPane page = loader.load();
    MenuController controller = loader.getController();

    page.setOnKeyPressed(event -> {
        switch (event.getCode()) {
        case F11:
            if (stage.isFullScreen()) {
                stage.setFullScreen(false);
            } else {
                stage.setFullScreen(true);
            }
            break;
        default:
            break;
        }
    });
    Scene scene = new Scene(page);
    scene.setOnKeyPressed(event -> {
        if (event.getCode() == KeyCode.A) {
            controller.printA();
        }
    });


    page.prefWidthProperty().bind(scene.widthProperty());
    page.prefHeightProperty().bind(scene.heightProperty());
    stage.setScene(scene);
    return controller ;
}

with

public class MenuController extends BorderPane{

    // existing code...

    public void printA() {
        System.out.println("A!");
    }

}

Just a comment: it makes absolutely no sense for MenuController to be a subclass of BorderPane (or any other UI class). I left that in, in case you need it elsewhere, but it completely violates the MVC pattern.

Additionally, I'm not really sure why you want the key handler for A to be on the scene, and the key handler for F11 to be on the root of the scene. It seems these should both be registered with the scene. But again, I left it as you had it in the question.