Q: Confused about switching screens JavaFX - javafx

Question

I dont understand how to switch between the current screen and the register screen:
package Computing;
import javafx.scene.layout.*;import javafx.application.Application;
import static javafx.application.Application.launch;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.geometry.HPos;
import javafx.geometry.Insets;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.scene.control.*;
import javafx.scene.text.Font;
import javafx.scene.text.FontWeight;
import javafx.stage.Stage;
import javafx.stage.Window;
public class Computing extends Application {
Stage stage;
#Override
public void start(Stage primaryStage) throws Exception {
stage = primaryStage;
primaryStage.setTitle("Computing Quiz");
GridPane gridPane = createComputingQuizPane();
// ui controls to gridpane
addUIControls(gridPane);
// scene
Scene scene = new Scene(gridPane, 800, 500);
// primary stage scene set
primaryStage.setScene(scene);
primaryStage.show();
}
private GridPane createComputingQuizPane() {
// Instantiate a new Grid Pane
GridPane gridPane = new GridPane();
gridPane.setAlignment(Pos.CENTER);
gridPane.setPadding(new Insets(40, 40, 40, 40));
gridPane.setHgap(10);
gridPane.setVgap(10);
return gridPane;
}
private void addUIControls(GridPane gridPane) {
// HEADER
Label headerLabel = new Label("Welcome to the Computing Quiz!");
headerLabel.setFont(Font.font("Arial", FontWeight.BOLD, 24));
gridPane.add(headerLabel, 0,0,2,1);
GridPane.setHalignment(headerLabel, HPos.CENTER);
GridPane.setMargin(headerLabel, new Insets(20, 0,20,0));
// LOGIN BUTTON
Button loginButton = new Button("Login");
loginButton.setPrefHeight(50);
loginButton.setDefaultButton(true);
loginButton.setPrefWidth(125);
gridPane.add(loginButton, 0, 4, 2, 1);
GridPane.setHalignment(loginButton, HPos.CENTER);
GridPane.setMargin(loginButton, new Insets(20, 0,20,0));
// REGISTER BUTTON
Button registerButton = new Button ("Register");
registerButton.setOnAction(e-> buttonClick());
registerButton.setPrefHeight(50);
registerButton.setDefaultButton(true);
registerButton.setPrefWidth(125);
gridPane.add(registerButton,0,5,2,1);
GridPane.setHalignment(registerButton,HPos.CENTER);
GridPane.setMargin(registerButton, new Insets(20,0,20,0));
//registerButton.setOnAction(new EventHandler<ActionEvent>() {
//#Override
//public void handle(ActionEvent event) {
//Register nc = new Register(stage);
//}
//});
}
public void buttonClick(){
Register nc = new Register(stage);
}
public static void main(String[] args) {
launch(args);
}
}
This is the register screen:
package Computing;
import javafx.application.Application;
import static javafx.application.Application.launch;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.geometry.HPos;
import javafx.geometry.Insets;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.scene.control.*;
import javafx.scene.layout.*;
import javafx.scene.text.Font;
import javafx.scene.text.FontWeight;
import javafx.stage.Stage;
import javafx.stage.Window;
public class Register {
Stage stage;
public Register (Stage s){
stage = s;
}
public void start(Stage primaryStage){
primaryStage.setTitle("Registration");
GridPane gridPane = createRegisterPane();
addUIControls(gridPane);
Scene scene = new Scene(gridPane, 800, 500);
primaryStage.setScene(scene);
primaryStage.show();
}
private GridPane createRegisterPane() {
GridPane gridPane = new GridPane();
gridPane.setAlignment(Pos.CENTER);
gridPane.setPadding(new Insets(40, 40, 40, 40));
gridPane.setHgap(10);
gridPane.setVgap(10);
return gridPane;
}
private void addUIControls(GridPane gridPane) {
// Add Header
Label headerLabel = new Label("Registration Form");
headerLabel.setFont(Font.font("Arial", FontWeight.BOLD, 24));
gridPane.add(headerLabel, 0,0,2,1);
GridPane.setHalignment(headerLabel, HPos.CENTER);
GridPane.setMargin(headerLabel, new Insets(20, 0,20,0));
// FULL NAME
Label nameLabel = new Label("Full Name : ");
gridPane.add(nameLabel, 0,1);
// FULL NAME TEXT
TextField nameField = new TextField();
nameField.setPrefHeight(40);
gridPane.add(nameField, 1,1);
// USERNAME
Label emailLabel = new Label("Username : ");
gridPane.add(emailLabel, 0, 2);
// EMAIL TEXT
TextField emailField = new TextField();
emailField.setPrefHeight(40);
gridPane.add(emailField, 1, 2);
// PASSWORD
Label passwordLabel = new Label("Password : ");
gridPane.add(passwordLabel, 0, 3);
// PASSWORD TEXT
PasswordField passwordField = new PasswordField();
passwordField.setPrefHeight(40);
gridPane.add(passwordField, 1, 3);
// SUBMIT BUTTON
Button submitButton = new Button("Submit");
submitButton.setPrefHeight(40);
submitButton.setDefaultButton(true);
submitButton.setPrefWidth(100);
gridPane.add(submitButton, 0, 4, 2, 1);
GridPane.setHalignment(submitButton, HPos.CENTER);
GridPane.setMargin(submitButton, new Insets(20, 0,20,0));
submitButton.setOnAction(new EventHandler<ActionEvent>() {
#Override
public void handle(ActionEvent event) {
if(nameField.getText().isEmpty()) {
showAlert(Alert.AlertType.ERROR, gridPane.getScene().getWindow(), "Error", "Please enter your name.");
return;
}
if(emailField.getText().isEmpty()) {
showAlert(Alert.AlertType.ERROR, gridPane.getScene().getWindow(), "Error", "Please enter a Username");
return;
}
if(passwordField.getText().isEmpty()) {
showAlert(Alert.AlertType.ERROR, gridPane.getScene().getWindow(), "Error!", "Please enter a password");
return;
}
showAlert(Alert.AlertType.CONFIRMATION, gridPane.getScene().getWindow(), "Registration Successful!", "Welcome " + nameField.getText());
}
});
}
private void showAlert(Alert.AlertType alertType, Window owner, String title, String message) {
Alert alert = new Alert(alertType);
alert.setTitle(title);
alert.setHeaderText(null);
alert.setContentText(message);
alert.initOwner(owner);
alert.show();
}
public static void main(String[] args) {
launch(args);
}
}
I've tried using this instead of the buttonClick method also I'm slightly confused as to why it won't work as before I used the same method using buttonClick to send the scene to the next screen
submitButton.setOnAction(new EventHandler<ActionEvent>() {
#Override
public void handle(ActionEvent event) {