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

Some Addition of @Sergey Grinev :

Create A custom Scene :

package sample;

import javafx.scene.Parent;
import javafx.scene.Scene;

public class DataPassingScene extends Scene {

    public DataPassingScene(Parent parent) {
        super(parent);
    }

    String tafsir;

    public String getTafsir() {
        return tafsir;
    }

    public void setTafsir(String tafsir) {
        this.tafsir = tafsir;
    }
}

Suppose your Main Class Name is App.java, Then Create a method to show new Stage :

public  static void showLayout (Stage primaryStage, String fxmlFileName, String stringData) throws IOException {

        Parent root = FXMLLoader.load(Objects.requireNonNull(App.class.getClassLoader().getResource(fxmlFileName)));
        DataPassingScene scene =  new DataPassingScene(root);

        scene.setTafsir(stringData); // Here we pass the data 

        primaryStage.setScene(scene);
        primaryStage.show();
    }

Now When you want to pass the Data, Call the above method from any Where / any class in your app with some Data :

      String tafsir = "This My Data" ; 

      try {
      App.showLayout(new Stage(), "showTafsirFxml.fxml",tafsir);
     } catch (IOException e) {
       e.printStackTrace();
    }

Then Get the data in your controller. To get the scene you have to get the stage, and to get the stage you have use one of your elements of FXML, suppose here your element is a button, called closeButton, So :

@FXML
    private Button closeButton;

@Override
    public void initialize(URL url, ResourceBundle rb) {

        Platform.runLater(new Runnable() {
            @Override public void run() {

                Stage stage = (Stage) closeButton.getScene().getWindow();
                DataPassingScene  scene = (DataPassingScene) stage.getScene();
                String s = scene.getTafsir(); // Here we get the Data
                if(s!=null)
                    System.out.println("This is Tafsir From Highlight Table: "+s);
                else         
                System.out.println("Data Passing Null");
            }});
 
    }

because, You have to wait some Times in above runLater, because for initializing scene take some time. Other wise scene will be null.

Answer 2

You can use controller for scenes and pass the data through controller:

String filePath1 =  "../" + fxmlfilename;
URL location1 = YourController1.class.getResource(filePath1);
FXMLLoader fxmlLoader = new FXMLLoader();
fxmlLoader.setLocation(location1);
fxmlLoader.setBuilderFactory(new JavaFXBuilderFactory());
Parent root = (Node) fxmlLoader.load(location1.openStream());

YourController1 ctrl1 = (YourController1) fxmlLoader.getController();

Then you can assign data to the controller:

ctrl1.setUserData();

Finally, just show the scene as you want:

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

//show the stage
stage.show();

In the initialize() method in the controller, just get data from controller as usual data object.

Answer 3

If you really want your scene to be meaningful (aka store specific user data) you can extend it:

public class FooScene extends Scene {
   private ObservableList myData;

   public setMyData(ObservableList data) {
       this.myData = data;
       //handle data
   }
}

The easiest way to make sure setup code is called after scene initialized it to call it by yourself:

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

        // first: add root to scene
        FooScene scene = new FooScene(root);
        // second: apply data to scene (or root)
        scene.setMyData(ol);
        stage.setScene(scene);

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

Answer 4

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