JavaFX include fxml in fxml without controller

Question

I'm programming an application with javafx. It's a "multiscreen" application with a mainmenu from where I can switch my scene.

My scenes are defined in different fxml files.

Because I try to use the mvc pattern I don't set the controller in the fxml files, I use setController on the FXMLloader.

Everything is working fine but I have the mainmenu and all its functions for the onActions in separate controller and in separate fxml file.

I've tried it with

<fx:include source="Menubar.fxml"/>

and created a controller for the fxml file, when I set the controller in the fxml file I can't compile the source. How do I set the controller for the included fxml file?

startpage.fxml gets its controller "Startpage" with

FXMLLoader loader = new FXMLLoader(getClass().getResource("../fxml/startpage.fxml"));
        loader.setController(new Startpage(m));
        Pane mainPane = loader.load();

startpage.fxml includes menubar.fxml, how to set a controller for the menubar controls now? Or how to include the menubarController easily in every other controller?

Answer 1

I think you need to use a controllerFactory in the loader to achieve what you want here. When you use a controllerFactory, you specify the classname of the controller in the FXML files, but the controller factory allows you to control how that is mapped to an object (so you can still construct it passing in a model, etc). When you specify a controllerFactory for an FXMLLoader, that factory is also used to create the controllers for any <fx:include>s that you have in the FXML file.

Finally, note that you can inject the controller for the included fxml file into the "main" fxml file, as documented in the "Nested controllers" section of the FXML documentation.

So if startpage.fxml looks like this:

<!-- imports etc -->
<BorderPane fx:controller="com.example.Startpage" ... >
  <top>
    <fx:include source="Menubar.fxml" fx:id="menubar" />
  </top>
  <!-- etc ... -->
</BorderPane>

and Menubar.fxml looks like

<!-- imports etc -->
<MenuBar fx:controller="com.example.MenubarController" ... >
  <!-- etc... -->
</MenuBar>

Then you can control the instantiation of the controller classes with:

FXMLLoader loader = new FXMLLoader(getClass().getResource("../fxml/startpage.fxml"));

Model m = ... ;

Startpage startpageController = new Startpage(m);
MenubarController menubarController = new MenubarController(m);

Callback<Class<?>, Object> controllerFactory = type -> {
    if (type == Startpage.class) {
        return startpageController ;
    } else if (type == MenubarController.class) {
        return menubarController ;
    } else { 
        // default behavior for controllerFactory:
        try {
            return type.newInstance();
        } catch (Exception exc) {
            exc.printStackTrace();
            throw new RuntimeException(exc); // fatal, just bail...
        }
    }
};

loader.setControllerFactory(controllerFactory);

Pane mainPane = loader.load();

Now you actually have references to both controllers in your application code, if you need, but you can also do

public class Startpage {

    public final Model m ;

    // note the name of this field must be xController,
    // where x is the fx:id set on the <fx:include>:

    @FXML
    private final MenubarController menubarController ;

    public Startpage(Model m) {
        this.m = m ;
    }

    // ...
}

So the main controller now has a reference to the menu bar controller.