MainActivity.kt

        seekBar.setOnSeekBarChangeListener(object : SeekBar.OnSeekBarChangeListener {
            override fun onStartTrackingTouch(p0: SeekBar?) {
            }

            override fun onStopTrackingTouch(p0: SeekBar?) {
                if (p0 != null) {
                    fernView.n = (p0.progress / 100.0 * MAX).toInt()
                    fernView.requestLayout()
                }
            }

            override fun onProgressChanged(p0: SeekBar?, p1: Int, p2: Boolean) {
            }
        })