Pass object from one scene to another

Question

As I'm learning the new world of JavaFX2 I stumbled on another annoying problem. I'm developing a program with multiple scenes (~10 scenes). For that I created a small class like this:

public class SceneSelector {
    ...
    public void setScene(Stage stage, String fxmlfilename, ObservableList ol) throws Exception{
        String s = "../" + fxmlfilename;
        Parent root = FXMLLoader.load(getClass().getResource(s));
        root.setUserData(ol);

        Scene scene = new Scene(root);
        stage.setScene(scene);

        //show the stage
        stage.show();
    }
}

This class works good enough for switching between the scenes. Now the problem is that I sometimes need to pass data from Scene1 to Scene2. I'm trying to do this by setting the setUserData() for the new scene which basicly works exept for one thing. How can I get the userdata when the new Scene is beeing initialized? (because the Nodes are still null at that time)

Code at scene1:

//Code connected to a button that opens the new Scene
private void openLabID(ActionEvent event) throws Exception {       
    final Stage primaryStage = (Stage) btnNewScene.getScene().getWindow();

    ObservableList<Koe> olAfTeWerkenKoeien = DA_Koe.getAfTeWerkenKoeien();
    ss.setScene(primaryStage, "GUI/scenes/koe/Koe.fxml", olAfTeWerkenKoeien);
}

Code at scene2:

public void initialize(URL url, ResourceBundle rb) {
    Scene s = lbl.getScene();
    ObservableList<Koe> olAfTeWerkenKoeien = (ObservableList<Koe>) s.getRoot().getUserData();
    System.out.println(olAfTeWerkenKoeien.size());
} 

Of course Scene s gives a null value at this point (because lbl is null at this point), so I wonder, is there a method that is beeing fired right after initialize?

When I attach this code to a button on Scene2, it works like a charm, but it should be loaded automatically.

EDIT: The setting of the data with the setMyData() method is not a problem, however retrieving it is:

public ObservableList<Koe> getMyData() {
   return this.myData;
}

How can I get the CustomScene object when a controller initializes? Because doing this below will result in a NullPointerException (because btnSluiten is not initialized just yet):

@Override
public void initialize(URL url, ResourceBundle rb) {
    ...
    Stage stage = (Stage) btnSluiten.getScene().getWindow();
    CustomScene cs = (CustomScene) stage.getScene();

    ObservableList<Koe> olKoe = cs.getMyData();

    System.out.println(olKoe.size());
}

Answer 1

I believe you missed the point within the Scene object. From the Scene class documentation we can see that:

The JavaFX Scene class is the container for all content in a scene graph.

Which means that the Scene object is just a container and as such it's not supposed to hold any data.

With that in mind, you can make another static object with a field such as

private static Label lbl;

...

public static Label getLbl()
{
    return MyStaticObject.Lbl;
}

...

and use it to store your lbl (or whatever object suits your information) and then statically retrieve it.

I'm doing that to set the owner of my other Stage objects from my application. I hope it helps. Cheers