Access elements of loaded FXML in Parent Controller - javafx

Question

I currently have the following situation:
I have created a FXML file backed up by a FXML Controller. The screen consists of a sidebar and a child holder. When I click on an element in the sidebar, I load an additional FXML file in the child holder, like this:
childHolder.getChildren().addAll(FXMLLoader.load(getClass().getResource("SidebarItem1.fxml")));
This works fine. But I want to access some elements of the loaded FXML in the Controller of the Parent Controller. I just initialized the elements of the child FXML after I loaded it.
I already looked at this question: JAVAFX - FXML - Access Loaded FXML Controls from Parent Controller, but when I do it like that, I still get an error:
FXMLLoader loader = new FXMLLoader(getClass().getResource("SidebarItem1.fxml"));
loader.setController(this);
childHolder.getChildren().addAll(loader.load());
someChildTextField.setText("Some text");
I have given someChildTextField a fx:id and I have placed it on top of the initialize like this:
#FXML public TextField someChildTextField;
Still, I get a NullpointerException, so I assume it can still not find the control.
Does anyone know how to access elements of a loaded FXML in the Parent Controller?

Answer 1

I can't see any reason your approach doesn't work; I mocked something similar up and it worked just fine. This is an unusual approach, though, as you are using the same object as a controller for two separate FXML files.
I would recommend using one controller for each FXML. So you could do something like
public class SidebarItem1Controller {
#FXML
private TextField someTextField ;
public void setText(String text) {
someTextField.setText(text);
}
}
and then from your parent controller just do
FXMLLoader loader = new FXMLLoader(getClass().getResource("SidebarItem1.fxml"));
childHolder.getChildren().add(loader.load());
SideBarItem1Controller childController = loader.getController();
childController.setText("Some Text");
Set the controller in your SideBarItem1.fxml file the usual way, with fx:controller = com.example.SidebarItem1Controller"