How to pass values from one stage to other

Question

I have two stage (say primary and secondary).The primary stage creates the secondary stage. When the secondary is opened i can access all the members(say bitNo) of 1st stage and try to set some value. But in the 1st stage i find the value not being set. I think it's because 1st is executed before the 2nd. I used showAndWait() in 1st then show() on 2nd then it is throwing exception.
So i want to use the values set by the 2nd stage in the 1st stage.
How do i synchronize them ?
Thanks .
package test;
import javafx.application.Application;
import javafx.event.*;
import javafx.scene.*;
import javafx.scene.control.*;
import javafx.scene.input.MouseEvent;
import javafx.scene.layout.*;
import javafx.stage.*;
public class Test extends Application {
    private int bitNo;
    Stage primaryStage,secondaryStage;   
    TextField textField;   
    double x,y;
    public static void main(String[] args) { launch(args); }
    @Override
    public void start(final Stage primaryStage) {
        this.primaryStage=primaryStage;
        Group rt=new Group();
        Scene sc= new Scene(rt,300,300);
        Button button =new Button("Click Me");
        button.setOnAction(new EventHandler<ActionEvent>() {
            @Override
            public void handle(ActionEvent event) {
                secondaryStage=new Stage(StageStyle.TRANSPARENT);
                secondaryStage.initModality(Modality.WINDOW_MODAL);
                secondaryStage.initOwner(primaryStage);    
                showSecondaryWindow();
        rt.getChildren().add(button);          
        primaryStage.setScene(sc);
        primaryStage.show();
        //primaryStage.showAndWait();
        System.out.println("Bit no set= "+bitNo);      
}//start
public void showSecondaryWindow(){
     Pane root=new Pane();
     root.setStyle("-fx-background-color: rgb(0,50,70);");
     //root.setPrefSize(200,200);
     Scene scene=new Scene(root,200,300);
     Label label=new Label("Data");
     textField=new TextField();
     textField.setUserData("one");
     Button ok=new Button("Ok");
     ok.setDefaultButton(true);
     ok.setOnMouseClicked(new EventHandler<MouseEvent>() {
        @Override
        public void handle(MouseEvent event) {
            System.out.println("New Stage Mouse Clicked");
            bitNo=Integer.parseInt(textField.getText());
            System.out.println("Bit no set by Secondary= "+bitNo);
            primaryStage.getScene().getRoot().setEffect(null);
            secondaryStage.close();
     Button cancel=ButtonBuilder.create().cancelButton(true).text("Cancel").build();
     cancel.setOnMouseClicked(new EventHandler<MouseEvent>() { 
         @Override
         public void handle(MouseEvent event) {
             System.out.println("New Stage Mouse Clicked");
             primaryStage.getScene().getRoot().setEffect(null);
             secondaryStage.close();
     //VBox vBox =new VBox();
     //vBox.getChildren().addAll(label,textField,ok);
     HBox dataFileds=new HBox(10);
     dataFileds.getChildren().addAll(label,textField);
     HBox buttons=new HBox(10);
     buttons.getChildren().addAll(cancel,ok);
     root.getChildren().add(VBoxBuilder.create().children(dataFileds,buttons).spacing(10).build());
     //scene.getStylesheets().add(Test.class.getResource("Modal.css").toExternalForm());
     secondaryStage.setScene(scene);
     //final Node root = secondaryStage.getScene().getRoot();
     root.setOnMousePressed(new EventHandler<MouseEvent>() {
         @Override public void handle(MouseEvent mouseEvent) {
             // record distance for the drag and drop operation.
             x = secondaryStage.getX() - mouseEvent.getScreenX();
             y = secondaryStage.getY() - mouseEvent.getScreenY();
     root.setOnMouseDragged(new EventHandler<MouseEvent>() {
         @Override public void handle(MouseEvent mouseEvent) {
             secondaryStage.setX(mouseEvent.getScreenX() +x);
             secondaryStage.setY(mouseEvent.getScreenY() +y);
     //primaryStage.getScene().getRoot().setEffect(new BoxBlur());
     secondaryStage.show();
}//showSecondaryWindow
}//class

Answer 1

You can use showAndWait() on your secondary stage. Then execution is blocked and you'll see the change to your variable:
package test ;
import javafx.application.Application;
import javafx.event.*;
import javafx.scene.*;
import javafx.scene.control.*;
import javafx.scene.input.MouseEvent;
import javafx.scene.layout.*;
import javafx.stage.*;
public class Test extends Application {
  private int bitNo;
  Stage primaryStage, secondaryStage;
  TextField textField;
  double x, y;
  public static void main(String[] args) {
    launch(args);
  @Override
  public void start(final Stage primaryStage) {
    this.primaryStage = primaryStage;
    Group rt = new Group();
    Scene sc = new Scene(rt, 300, 300);
    Button button = new Button("Click Me");
    button.setOnAction(new EventHandler<ActionEvent>() {
      @Override
      public void handle(ActionEvent event) {
        secondaryStage = new Stage(StageStyle.TRANSPARENT);
        secondaryStage.initModality(Modality.WINDOW_MODAL);
        secondaryStage.initOwner(primaryStage);
        // This calls showAndWait(), so execution blocks until the window is closed
        showSecondaryWindow();
        // secondary window is now closed, value should be updated:
        System.out.println("Bit no now: " + bitNo);
    rt.getChildren().add(button);
    primaryStage.setScene(sc);
    primaryStage.show();
    // primaryStage.showAndWait();
    System.out.println("Bit no set= " + bitNo);
  }// start
  public void showSecondaryWindow() {
    Pane root = new Pane();
    root.setStyle("-fx-background-color: rgb(0,50,70);");
    // root.setPrefSize(200,200);
    Scene scene = new Scene(root, 200, 300);
    Label label = new Label("Data");
    textField = new TextField();
    textField.setUserData("one");
    Button ok = new Button("Ok");
    ok.setDefaultButton(true);
    ok.setOnMouseClicked(new EventHandler<MouseEvent>() {
      @Override
      public void handle(MouseEvent event) {
        System.out.println("New Stage Mouse Clicked");
        bitNo = Integer.parseInt(textField.getText());
        System.out.println("Bit no set by Secondary= " + bitNo);
        primaryStage.getScene().getRoot().setEffect(null);
        secondaryStage.close();
    Button cancel = ButtonBuilder.create().cancelButton(true).text("Cancel")
        .build();
    cancel.setOnMouseClicked(new EventHandler<MouseEvent>() {
      @Override
      public void handle(MouseEvent event) {
        System.out.println("New Stage Mouse Clicked");
        primaryStage.getScene().getRoot().setEffect(null);
        secondaryStage.close();
    // VBox vBox =new VBox();
    // vBox.getChildren().addAll(label,textField,ok);
    HBox dataFileds = new HBox(10);
    dataFileds.getChildren().addAll(label, textField);
    HBox buttons = new HBox(10);
    buttons.getChildren().addAll(cancel, ok);
    root.getChildren().add(
        VBoxBuilder.create().children(dataFileds, buttons).spacing(10).build());
    // scene.getStylesheets().add(Test.class.getResource("Modal.css").toExternalForm());
    secondaryStage.setScene(scene);
    // final Node root = secondaryStage.getScene().getRoot();
    root.setOnMousePressed(new EventHandler<MouseEvent>() {
      @Override
      public void handle(MouseEvent mouseEvent) {
        // record distance for the drag and drop operation.
        x = secondaryStage.getX() - mouseEvent.getScreenX();
        y = secondaryStage.getY() - mouseEvent.getScreenY();
    root.setOnMouseDragged(new EventHandler<MouseEvent>() {
      @Override
      public void handle(MouseEvent mouseEvent) {
        secondaryStage.setX(mouseEvent.getScreenX() + x);
        secondaryStage.setY(mouseEvent.getScreenY() + y);
    // primaryStage.getScene().getRoot().setEffect(new BoxBlur());
    secondaryStage.showAndWait();
  }// showSecondaryWindow
}// classYou can also use an IntegerProperty to hold the variable, and listen for changes on it:
package test ;
import javafx.application.Application;
import javafx.beans.property.IntegerProperty;
import javafx.beans.property.SimpleIntegerProperty;
import javafx.beans.value.ChangeListener;
import javafx.beans.value.ObservableValue;
import javafx.event.*;
import javafx.scene.*;
import javafx.scene.control.*;
import javafx.scene.input.MouseEvent;
import javafx.scene.layout.*;
import javafx.stage.*;
public class Test extends Application {
  private IntegerProperty bitNo;
  Stage primaryStage, secondaryStage;
  TextField textField;
  double x, y;
  public static void main(String[] args) {
    launch(args);
  @Override
  public void start(final Stage primaryStage) {
    this.bitNo = new SimpleIntegerProperty();
    bitNo.addListener(new ChangeListener<Number>() {
      @Override
      public void changed(ObservableValue<? extends Number> observable,
          Number oldValue, Number newValue) {
        System.out.printf("bit no changed from %d to %d%n", oldValue, newValue);
    this.primaryStage = primaryStage;
    Group rt = new Group();
    Scene sc = new Scene(rt, 300, 300);
    Button button = new Button("Click Me");
    button.setOnAction(new EventHandler<ActionEvent>() {
      @Override
      public void handle(ActionEvent event) {
        secondaryStage = new Stage(StageStyle.TRANSPARENT);
        secondaryStage.initModality(Modality.WINDOW_MODAL);
        secondaryStage.initOwner(primaryStage);
        showSecondaryWindow();
    rt.getChildren().add(button);
    primaryStage.setScene(sc);
    primaryStage.show();
    // primaryStage.showAndWait();
    System.out.println("Bit no set= " + bitNo.get());
  }// start
  public void showSecondaryWindow() {
    Pane root = new Pane();
    root.setStyle("-fx-background-color: rgb(0,50,70);");
    // root.setPrefSize(200,200);
    Scene scene = new Scene(root, 200, 300);
    Label label = new Label("Data");
    textField = new TextField();
    textField.setUserData("one");
    Button ok = new Button("Ok");
    ok.setDefaultButton(true);
    ok.setOnMouseClicked(new EventHandler<MouseEvent>() {
      @Override
      public void handle(MouseEvent event) {
        System.out.println("New Stage Mouse Clicked");
        bitNo.set(Integer.parseInt(textField.getText()));
        System.out.println("Bit no set by Secondary= " + bitNo);
        primaryStage.getScene().getRoot().setEffect(null);
        secondaryStage.close();
    Button cancel = ButtonBuilder.create().cancelButton(true).text("Cancel")
        .build();
    cancel.setOnMouseClicked(new EventHandler<MouseEvent>() {
      @Override
      public void handle(MouseEvent event) {
        System.out.println("New Stage Mouse Clicked");
        primaryStage.getScene().getRoot().setEffect(null);
        secondaryStage.close();
    // VBox vBox =new VBox();
    // vBox.getChildren().addAll(label,textField,ok);
    HBox dataFileds = new HBox(10);
    dataFileds.getChildren().addAll(label, textField);
    HBox buttons = new HBox(10);
    buttons.getChildren().addAll(cancel, ok);
    root.getChildren().add(
        VBoxBuilder.create().children(dataFileds, buttons).spacing(10).build());
    // scene.getStylesheets().add(Test.class.getResource("Modal.css").toExternalForm());
    secondaryStage.setScene(scene);
    // final Node root = secondaryStage.getScene().getRoot();
    root.setOnMousePressed(new EventHandler<MouseEvent>() {
      @Override
      public void handle(MouseEvent mouseEvent) {
        // record distance for the drag and drop operation.
        x = secondaryStage.getX() - mouseEvent.getScreenX();
        y = secondaryStage.getY() - mouseEvent.getScreenY();
    root.setOnMouseDragged(new EventHandler<MouseEvent>() {
      @Override
      public void handle(MouseEvent mouseEvent) {
        secondaryStage.setX(mouseEvent.getScreenX() + x);
        secondaryStage.setY(mouseEvent.getScreenY() + y);
    // primaryStage.getScene().getRoot().setEffect(new BoxBlur());
    secondaryStage.show();
  }// showSecondaryWindow
}// class