计时器未递增

Question

我正在尝试实现一个计时器，并且希望它显示在屏幕上。我能够使它显示出来，但不能在每个屏幕上递增。有人可以帮我吗？

代码如下：

// Screen Size
int gameWidth = 1000;
int gameHeight = 700;
// Timer
long endTime = System.currentTimeMillis();
Label timeLabel = new Label();
DateFormat timeFormat = new SimpleDateFormat("HH:mm:ss");
final Timeline timeline = new Timeline(
    new KeyFrame(
        Duration.seconds(1),
        event -> {
            final long diff = endTime - System.currentTimeMillis();
            if (diff < 0) {
                // timeLabel.setText("00:00:00");
                timeLabel.setText(timeFormat.format(0));
            } else {
                timeLabel.setText(timeFormat.format(diff));
            }
        })
    );
    timeline.setCycleCount(Timeline.INDEFINITE);
    timeline.play();
    // Background Image
    StackPane gameBackgroundImgContainer = new StackPane();
    ImageView gameBgImage = new ImageView("stoneBG.jpg");
    gameBgImage.setFitHeight(gameHeight + 100);
    gameBgImage.setFitWidth(gameWidth + 500);
    gameBackgroundImgContainer.getChildren().addAll(gameBgImage, gameBorder);
    game = new Scene(gameBackgroundImgContainer, gameWidth, gameHeight);