private var scheduler: ScheduledExecutorService? = null

    fun timerStart() {

        scheduler = Executors.newSingleThreadScheduledExecutor()

        scheduler?.scheduleWithFixedDelay({
            var time = elapsed(startTime, LocalDateTime.now())
            timerLiveData.postValue(Pair(TIMER.TIMER, time))
        }, 0, 1, TimeUnit.SECONDS)

    }


    fun timerStop() {

        scheduler?.let {
            if (!it.isShutdown) {
                it.shutdown() // 优雅关闭（允许当前任务执行完毕）
                // 可选：如果需要立即终止任务，使用 it.shutdownNow()
            }
        }
        scheduler = null
    }

    fun timerReset() {
        startTime = LocalDateTime.now()
    }