StopwatchVIewHolder.kt

class StopwatchViewHolder(
    private val binding: StopwatchItemBinding
): RecyclerView.ViewHolder(binding.root) {

    private var timer: CountDownTimer? = null

    fun bind(stopwatch: Stopwatch) {
        binding.stopwatchTimer.text = stopwatch.currentMs.displayTime()

        if (stopwatch.isStarted) {
            startTimer(stopwatch)
        }
    }

    private fun startTimer(stopwatch: Stopwatch) {
        timer?.cancel()
        timer = getCountDownTimer(stopwatch)
        timer?.start()
    }

    private fun getCountDownTimer(stopwatch: Stopwatch): CountDownTimer {
        return object : CountDownTimer(PERIOD, UNIT_TEN_MS) {
            val interval = UNIT_TEN_MS

            override fun onTick(millisUntilFinished: Long) {
                stopwatch.currentMs += interval
                binding.stopwatchTimer.text = stopwatch.currentMs.displayTime()
            }

            override fun onFinish() {
                binding.stopwatchTimer.text = stopwatch.currentMs.displayTime()
            }
        }
    }
    
 /*...*/
 
 private companion object {

        private const val START_TIME = "00:00:00:00"
        private const val UNIT_TEN_MS = 10L
        private const val PERIOD  = 1000L * 60L * 60L * 24L // Day
    }
  
}