Multiple buttons and their event handlers in JavaFX

Question

In my project I used this code to create a GUI using JavaFX. The aim was to have a screen with 7 buttons on it. Next, depending on which button is pressed another set of buttons will appear on the screen. The user then chooses one of these which then sets an integer variable subchapter to a value and calls the next methods. However, from looking at my code to do this, it seems very inefficient and I was wondering if there was a better way to code this.

Firstly, this is my code to declare the buttons I use:

Label choice;
Button chapter1;
Button chapter2;
Button chapter3;
Button chapter4;
Button chapter5;
Button chapter6;
Button chapter7;
public int subchapter = 0;

Next this is the code where I use the buttons:

private void chooseQuiz() {


    root.getChildren().clear();
    choice = new Label();
    choice.setText("Please choose a chapter ");
    choice.setLayoutX(50);
    choice.setLayoutY(0);


    chapter1 = new Button();
    chapter1.setText("Applied Anatomy and physiology");
    chapter1.setLayoutX(30);
    chapter1.setLayoutY(50);
    chapter1.setWrapText(true);
    chapter1.setOnAction(event -> {
        root.getChildren().clear();
        choice.setText("Please choose a topic");
        chapter1.setText("The cardiovascular and respiratory system");
        chapter1.setOnAction(event1 -> {
            subchapter = 1;
            getQuestionsAndScores();
            runQuiz();
        });
        chapter2.setText("The neuromuscular and musculoskeletal system");
        chapter2.setOnAction(event1 -> {
            subchapter = 2;
            getQuestionsAndScores();
            runQuiz();
        });
        chapter3.setText("Energy systems");
        chapter3.setOnAction(event1 -> {
            subchapter = 3;
            getQuestionsAndScores();
            runQuiz();
        });
        root.getChildren().addAll(choice, chapter1, chapter2, chapter3);
    });

    chapter2 = new Button();
    chapter2.setText("Skill acquisition");
    chapter2.setLayoutX(30);
    chapter2.setLayoutY(150);
    chapter2.setWrapText(true);
    chapter2.setOnAction(event -> {
        root.getChildren().clear();
        choice.setText("Please choose a topic");
        chapter1.setText("Skill classifications and Information processing and transfer of skills");
        chapter1.setOnAction(event1 -> {
            subchapter = 4;
            getQuestionsAndScores();
            runQuiz();
        });
        chapter2.setText("Theories of learning and guidance and feedback and methods of presenting practice");
        chapter2.setOnAction(event1 -> {
            subchapter = 5;
            getQuestionsAndScores();
            runQuiz();
        });
        root.getChildren().addAll(choice, chapter1, chapter2);
    });

    chapter3 = new Button();
    chapter3.setText("Sport and society");
    chapter3.setLayoutX(30);
    chapter3.setLayoutY(250);
    chapter3.setWrapText(true);
    chapter3.setOnAction(event -> {
        root.getChildren().clear();
        choice.setText("Please choose a topic");
        chapter1.setText("Pre-industrial/industrial/post industrial sport");
        chapter1.setOnAction(event1 -> {
            subchapter = 6;
            getQuestionsAndScores();
            runQuiz();
        });
        chapter2.setText("Sociology in sport");
        chapter2.setOnAction(event1 -> {
            subchapter = 7;
            getQuestionsAndScores();
            runQuiz();
        });
        root.getChildren().addAll(choice, chapter1, chapter2);
    });

    chapter4 = new Button();
    chapter4.setText("Exercise physiology");
    chapter4.setLayoutX(30);
    chapter4.setLayoutY(350);
    chapter4.setWrapText(true);
    chapter4.setOnAction(event -> {
        root.getChildren().clear();
        choice.setText("Please choose a topic");
        chapter1.setText("Diet and nutrition and training methods and injury prevention and rehabilitation");
        chapter1.setOnAction(event1 -> {
            subchapter = 8;
            getQuestionsAndScores();
            runQuiz();
        });
        root.getChildren().addAll(choice, chapter1);
    });

    chapter5 = new Button();
    chapter5.setText("Biomechanical movement");
    chapter5.setLayoutX(30);
    chapter5.setLayoutY(450);
    chapter5.setWrapText(true);
    chapter5.setOnAction(event -> {
        root.getChildren().clear();
        choice.setText("Please choose a topic");
        chapter1.setText("Biomechanical principles and levers");
        chapter1.setOnAction(event1 -> {
            subchapter = 9;
            getQuestionsAndScores();
            runQuiz();
        });
        chapter2.setText("Linear motion and Angular motion ");
        chapter2.setOnAction(event1 -> {
            subchapter = 10;
            getQuestionsAndScores();
            runQuiz();
        });
        chapter3.setText("Projectile motion and Fluid mechanics");
        chapter3.setOnAction(event1 -> {
            subchapter = 11;
            getQuestionsAndScores();
            runQuiz();
        });
        root.getChildren().addAll(choice, chapter1, chapter2, chapter3);
    });

    chapter6 = new Button();
    chapter6.setText("Sport Psychology");
    chapter6.setLayoutX(30);
    chapter6.setLayoutY(550);
    chapter6.setWrapText(true);
    chapter6.setOnAction(event -> {
        root.getChildren().clear();
        choice.setText("Please choose a topic");
        chapter1.setText("Personality and attitudes");
        chapter1.setOnAction(event1 -> {
            subchapter = 12;
            getQuestionsAndScores();
            runQuiz();
        });
        chapter2.setText("Arousal and anxiety");
        chapter2.setOnAction(event1 -> {
            subchapter = 13;
            getQuestionsAndScores();
            runQuiz();
        });
        chapter3.setText("Aggression and motivation");
        chapter3.setOnAction(event1 -> {
            subchapter = 14;
            getQuestionsAndScores();
            runQuiz();
        });
        chapter4.setText("Achievement motivation and self-efficacy");
        chapter4.setOnAction(event1 -> {
            subchapter = 15;
            getQuestionsAndScores();
            runQuiz();
        });
        chapter5.setText("Social facilitation and group dynamics and goal setting");
        chapter5.setOnAction(event1 -> {
            subchapter = 16;
            getQuestionsAndScores();
            runQuiz();
        });
        chapter6.setText("Attribution theory and leadership and stress management");
        chapter6.setOnAction(event1 -> {
            subchapter = 17;
            getQuestionsAndScores();
            runQuiz();
        });
        root.getChildren().addAll(choice, chapter1, chapter2, chapter3, chapter4, chapter5, chapter6);
    });

    chapter7 = new Button();
    chapter7.setText("Sport and society and technology in sport");
    chapter7.setLayoutX(30);
    chapter7.setLayoutY(650);
    chapter7.setWrapText(true);
    chapter7.setOnAction(event -> {
        root.getChildren().clear();
        choice.setText("Please choose a topic");
        chapter1.setText("Physical activity and sport and the development of elite performers");
        chapter1.setOnAction(event1 -> {
            subchapter = 18;
            getQuestionsAndScores();
            runQuiz();
        });
        chapter2.setText("Ethics and violence in sport");
        chapter2.setOnAction(event1 -> {
            subchapter = 19;
            getQuestionsAndScores();
            runQuiz();
        });
        chapter3.setText("Drugs in sport and sport and the law");
        chapter3.setOnAction(event1 -> {
            subchapter = 20;
            getQuestionsAndScores();
            runQuiz();
        });
        chapter4.setText("Commercialisation");
        chapter4.setOnAction(event1 -> {
            subchapter = 21;
            getQuestionsAndScores();
            runQuiz();
        });
        chapter5.setText("Technology in sport");
        chapter5.setOnAction(event1 -> {
            subchapter = 22;
            getQuestionsAndScores();
            runQuiz();
        });
        root.getChildren().addAll(choice, chapter1, chapter2, chapter3, chapter4, chapter5);
    });


    root.getChildren().addAll(choice, chapter1, chapter2, chapter3, chapter4, chapter5, chapter6, 
    chapter7);

    Scene scene = new Scene(root, 500, 800);
    subStage.setScene(scene);
    subStage.show();
}
```

Answer 1

First thing that comes to mind is subclassing Button, perhaps nesting it in your main class so it can easily modify class variables:

import javafx.scene.control.Button;
import javafx.scene.layout.Pane;
import javafx.event.EventHandler;
import javafx.event.ActionEvent;

public class Quiz {

    private int subchapter;
    private Pane root = new Pane();

    private void chooseQuiz() {
        MyButton chapter1 = new MyButton("Skill acquisition", 30, 150, e -> {...});
        chapter1.setSubchapter(18);
    }
    private void getQuestionsAndScores() {...}
    private void runQuiz() {...}

    private class MyButton extends Button {
        private MyButton(String text, int x, int y, EventHandler<ActionEvent> onClick) {
            super(text);
            this.setLayoutX(30);
            this.setLayoutY(50);
            this.setWrapText(true);
            this.setOnAction(onClick);
            root.getChildren().add(this);
        }
        private void setSubchapter(int value) {
            this.setOnAction(e -> {
                subchapter = value;
                getQuestionsAndScores();
                runQuiz();
            });
        }
    }
}

This is essentially streamlining your code, delegating verbose code and repetitive calls to the constructor/class functions, which I assume is what you mean by "efficient".

EDIT:

As mjt pointed out, this could be considered an abuse of inheritance. A more proper way that avoids the use of inheritance would be using functions:

import javafx.scene.control.Button;
import javafx.scene.layout.Pane;
import javafx.event.EventHandler;
import javafx.event.ActionEvent;

public class Quiz {

    private int subchapter;
    private Pane root = new Pane();

    private void chooseQuiz() {
        MyButton chapter1 = createButton("Skill acquisition", 30, 150, e -> {...});
        setSubchapter(chapter1, 18);
    }
    private void getQuestionsAndScores() {...}
    private void runQuiz() {...}

    private Button createButton(String text, int x, int y, EventHandler<ActionEvent> onClick) {
        Button button = new Button();
        button.setText(text);
        button.setLayoutX(x);
        button.setLayoutY(y);
        button.setWrapText(true);
        button.setOnAction(onClick);
        root.getChildren().add(button);
        return button;
    }
    private void setSubchapter(Button target, int value) {
        target.setOnAction(e -> {
            subchapter = value;
            getQuestionsAndScores();
            runQuiz();
        });
    }
}

```