pickerHours.setOnValueChangedListener { picker, oldVal, newVal ->
            timerString = pickerHours.value.toString() + ":" + pickerMinutes.value.toString() + ":" + newVal
        }

    pickerMinutes.setOnValueChangedListener { picker, oldVal, newVal ->
        timerString1 = pickerHours.value.toString() + ":" + newVal + ":" + pickerSeconds.value
    }
    pickerSeconds.setOnValueChangedListener { picker, oldVal, newVal ->
        timerString2 = pickerHours.value.toString() + ":" + pickerMinutes.value.toString() + ":" + newVal

calculateBtn.setOnClickListener {
when {

            timerString.isEmpty() && timerString1.isEmpty() && timerString2.isEmpty() && (distance.text.isNotEmpty() && pace.text.isNotEmpty()) ->
                calculatePace(null, distance.text.toString().toDouble(), pace.text.toString())

            distance.text.isEmpty() && (timerString.isNotEmpty() && timerString1.isNotEmpty() && timerString2.isNotEmpty() && pace.text.isNotEmpty()) ->
                calculatePace(time.text.toString(), null, pace.text.toString())

            (timerString.isNotEmpty() && timerString1.isNotEmpty() && timerString2.isNotEmpty() && distance.text.isNotEmpty()) ->
                calculatePace(time.text.toString(), distance.text.toString().toDouble(), null)


            else -> {
                Toast.makeText(this, "Please check fields",
                        Toast.LENGTH_SHORT).show()
            }
        }

    }