Example app

Mini quiz

Buttons, answer feedback and once-only scoring.

Run this example

Stop the app and save your current Main and helpers outside src/. Copy the files shown below into the listed destinations in your standalone starter, creating resource folders when needed. Replace Main and the listed helpers. Keep the zero/ framework folder and build files. If an older downloaded kit does not have these examples, use the source shown here.

examples/quiz/Main.java → src/main/java/Main.java
examples/shared/ScoreDisplay.java → src/main/java/ScoreDisplay.java

Run App to rebuild. These examples run in VS Code, in a separate JavaFX window.

Open related lesson

Read the source

quiz/Main.java

import javafx.geometry.Insets;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.control.TextField;
import javafx.scene.layout.VBox;
import zero.SimpleApp;

/** Start here: fields, objects, and a method called by a button click. */
public class Main extends SimpleApp {
    private int points;
    private TextField answer;
    private Label feedback;
    private Button check;
    private ScoreDisplay score;

    @Override public void settings() {
        title("Mini quiz");
        size(420, 300);
    }

    @Override public void setup() {
        Label question = new Label("What is 6 × 7?");
        answer = new TextField();
        answer.setPromptText("Answer");
        check = new Button("Check answer");
        feedback = new Label("Enter an answer.");
        score = new ScoreDisplay();
        check.setOnAction(event -> checkAnswer());
        VBox screen = new VBox(12, question, answer, check, feedback, score.view());
        screen.setPadding(new Insets(20));
        show(screen);
    }

    private void checkAnswer() {
        if (answer.getText().trim().equals("42")) {
            points += 10;
            score.setScore(points);
            feedback.setText("Correct!");
            check.setDisable(true); // Award this question only once.
        } else {
            feedback.setText("Try again.");
        }
    }

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

shared/ScoreDisplay.java

import javafx.scene.Node;
import javafx.scene.control.Label;

/** An ordinary class: the app owns the number; this object displays it. */
public class ScoreDisplay {
    private final Label label;
    private final String caption;

    public ScoreDisplay() {
        this("Score");
    }

    public ScoreDisplay(String caption) {
        this.caption = caption;
        label = new Label(caption + ": 0");
    }

    public void setScore(int points) {
        label.setText(caption + ": " + points);
    }

    public Node view() {
        return label;
    }
}