start method

void start()

启动倒计时

Implementation

void start() {
  // 先取消旧的定时器，确保唯一性
  _timer?.cancel();

  // 重置剩余时间
  _remainingSeconds = maxSeconds;
  _updateDisplay();

  // 启动定时器，每秒减1
  _timer = Timer.periodic(const Duration(seconds: 1), (timer) {
    if (_remainingSeconds > 0) {
      _remainingSeconds--;
      _updateDisplay();
    } else {
      // 倒计时结束
      _timer?.cancel();
      _timer = null;
      onComplete?.call();
    }
  });
}