JavaFX Passing Stage/Switching Scene

Question

I have decided to update my application using JavaFXML, However I am having difficulties passing a scene into my controller. Here is my Controller;

public class MainApp extends Application {

@FXML
public Stage primaryStage;

@FXML
private AnchorPane rootLayout;
@FXML
private JobInterface jInterface;

@Override
public void start(Stage primaryStage) {
    primaryStage = new Stage();
    setPrimaryStage(primaryStage);
    initRootLayout();
}

@FXML
public void initRootLayout(){
    try {
        primaryStage = getPrimaryStage();
        FXMLLoader loader = new FXMLLoader();
        loader.setLocation(MainApp.class.getResource("MainInterface.fxml"));
        rootLayout = (AnchorPane) loader.load();        
        Scene scene = new Scene(rootLayout);    
        primaryStage.setScene(scene);
        primaryStage.show();
        setPrimaryStage(primaryStage);
    } catch (IOException e) {
        e.printStackTrace();
    }
}

@FXML
private void setJobLayout(){
    primaryStage = getPrimaryStage();
    jInterface = new JobInterface();
    jInterface.initJobLayout();
    primaryStage.setScene(jInterface.getScene());
}

public static void main(String[] args) {
    launch(args);
}

public Stage getPrimaryStage() {
    return primaryStage;
}

public void setPrimaryStage(Stage primaryStage) {
    this.primaryStage = primaryStage;
}
}

Here is a method that is changing the scene using a different FXML file and attempting to pass the scene back to the controller;

public class JobInterface {

private AnchorPane rootLayout;
private Scene scene;

public void initJobLayout(){
    try {
        FXMLLoader loader = new FXMLLoader();
        loader.setLocation(MainApp.class.getResource("JobInterface.fxml"));
        rootLayout = (AnchorPane) loader.load();
        scene = new Scene(rootLayout);
        setScene(scene);
    } catch (IOException e) {
        e.printStackTrace();
    }
}

public Scene getScene() {
    return scene;
}

public void setScene(Scene scene) {
    this.scene = scene;
}
}

The issue I'm having now is a NullPointerException on this line in the main app;

primaryStage.setScene(jInterface.getScene());

I am trying to pass a Stage between methods so that I can only update the Scene and not have to open a new Stage everytime a new method is called. Any ideas on where I am going wrong?

Answer 1

There should be no need to pass the stage or scene. Your Main will load the fxml resource which will have your fxml controller 'in charge' of your fxml file.

    @Override
    public void start(Stage stage) throws Exception {
    Parent root = FXMLLoader.load(getClass().getResource("jobController.fxml"));        
    Scene scene = new Scene(root);        
    stage.setScene(scene);
    stage.show();
}

Your controller might look something like this (depending on your fxml design):

public class JobController {

    @FXML
    private Label label;

    @FXML
    private void handleButtonAction(ActionEvent event) {        
        label.setText("This is the controller speaking");
    } 
}

Now you can 'control' your stage (scene) from the controller. If you are going to create another class which also has to update the scene, pass a reference to the controller to it eg from the controller:

TimeClock timeClock = new TimeClock();
timeClock.init(this);

and then in TimeClock.java you have:

private final JobController controller;

public void init (JobController control){ 
    this.controller = control;
}

Now you can access any public method in your controller from the TimeClock class. Eg

controller.updateLabel("Time clock speaking!");