JavaFX: Passing Arguments with FXMLLoader to own class [duplicate] - javafx

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This question already has answers here:
JavaFX : Pass parameters while instantiating controller class
(2 answers)
Closed 23 days ago.
Edit: I believe I found the correct answer to my problem after all.
Original Post:
I'm currently trying to create an application with JavaFX and an EventBus-System. To do this, I have to pass the EventBus as constructor argument to other classes when instantiating them. However I don't know how to do this while also using an FXMLLoader to load my .fxml-Files.
My code currently looks somethinng like this:
Main Class
public class MyApplication extends Application {
public void start(Stage stage) throws Exception {
EventBus eventBus = new EventBus();
>>> Here would be code that creates an Object of MainView, passing eventBus as constructor argument. <<<
Scene scene = new Scene(mainView);
stage.setScene(scene);
stage.show();
}
public static void main(String[] args) {
launch(args);
}
}
This class inherits from BorderPane and I want to create an object of it using fxmlLoader (I think. I'm not sure if it works like that)
puplic class MainView extends BorderPane {
private EventBus eventBus;
public MainView(EventBus eventBus) {
this.eventBus = eventBus;
... other code
}
}
I also have a controller for MainView (don't know if thats important to mention)
public class MainViewController {
>>> several JavaFX Elements like buttons, labels etc and their associated functionalities like onActions and such... <<<<
}
And of course there is an .fxml-File that contains the actual design of the MainView that I created with SceneBuilder, but I won't post it here since it doesn't seem necessary. But I sould probably mention that this .fxml-File contains a BorderPane as it's highest node. I think that makes sense, since my MainView extends BorderPane.
My Problem is that I ever created my own class that extends BorderPane and needs a Constructor parameter before and I don't really know how to create an instance of it.
In the past I did something like this:
FXMLLoader loader = new FXMLLoader();
BorderPane root = loader.load(getClass().getResourceAsStream("MainView.fxml"));
Scene scene = new Scene(root);
stage.show();
I of course looked for solutions online but those posts talk about passing arguments between windows and such.
Thanks in advance for your help.

Answer 1

You can use a dynamic root in the FXML.
Briefly, the FXML will look like:
<fx:root
type="javafx.scene.layout.BorderPane"
xmlns:fx="http://javafx.com/fxml"
fx:controller="com.mycompany.myproject.MainViewController">
<!-- Controls etc. -->
</fx:root>
And then in the MainView constructor do
public class MainView extends BorderPane {
private EventBus eventBus;
public MainView(EventBus eventBus) {
this.eventBus = eventBus;
FXMLLoader loader = new FXMLLoader(getClass().getResourceAsStream("MainView.fxml"));
loader.setRoot(this);
loader.load();
}
}
The controller will just behave the same as the controller in an FXML with a static root. That is, you could communicate with the controller if needed with:
public MainView(EventBus eventBus) {
this.eventBus = eventBus;
FXMLLoader loader = new FXMLLoader(getClass().getResourceAsStream("MainView.fxml"));
loader.setRoot(this);
loader.load();
MainViewController controller = loader.getController();
// etc...
}
or if you needed to instantiate it by hand, omit the fx:controller attribute from the FXML file, and then do
public MainView(EventBus eventBus) {
this.eventBus = eventBus;
MainViewController controller = new MainViewController(...);
FXMLLoader loader = new FXMLLoader(getClass().getResourceAsStream("MainView.fxml"));
loader.setRoot(this);
loader.setController(controller);
loader.load();
}