ExampleB.java

public class BouncingBalls extends GraphicsApp {

    private static final int CANVAS_WIDTH = 1280;
    private static final int CANVAS_HEIGHT = 360;
    private static final Color BACKGROUND_COLOR = Colors.WHITE;

    private Circle circle;
    private boolean isMovingRight = true;
    private int currentSpeed = 10;

    @Override
    public void initialize() {
        setCanvasSize(CANVAS_WIDTH, CANVAS_HEIGHT);
        circle = new Circle(CANVAS_WIDTH / 2, CANVAS_HEIGHT / 2, 25, Colors.RED);
    }

    @Override
    public void draw() {
        drawBackground(BACKGROUND_COLOR);
        updateCircle();
        circle.draw();
    }

    // Diese Methode bewegt den Kreis mit der aktuellen Geschwindigkeit in die aktuelle Bewegungsrichtung und ändert diese ggf.
    private void updateCircle() {
        if (isMovingRight) {
            circle.move(currentSpeed, 0);
        } else {
            circle.move(-currentSpeed, 0);
        }
        if (circle.getXPos() - circle.getRadius() > CANVAS_WIDTH) {
            isMovingRight = false;
        }
        if (circle.getXPos() < -circle.getWidth()) {
            isMovingRight = true;
        }
    }

    // Bei Tastendruck wird die Bewegungsgeschwindigkeit angepasst
    @Override
    public void onKeyPressed(KeyPressedEvent event) {
        super.onKeyPressed(event);
        if (event.getKeyCode() == KeyPressedEvent.VK_UP) {
            currentSpeed++;
        }
        if (event.getKeyCode() == KeyPressedEvent.VK_DOWN) {
            currentSpeed--;
        }
        if (currentSpeed <= 0) {
            currentSpeed = 1;
        }
    }

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