Custom View #2 (onTouchEvent)

import android.content.Context
        import android.graphics.Canvas
        import android.graphics.Color
        import android.graphics.Paint
        import android.util.AttributeSet
        import android.view.MotionEvent
        import android.view.View

class TestView(
    context: Context,
    attributeSet: AttributeSet
) : View(context, attributeSet) {
    private val paint = Paint()
    private val paintC = Paint()
    private val startAngle = -180f
    private val colors = listOf(
        Color.RED,
        Color.BLUE,
        Color.GREEN,
        Color.YELLOW
    )
    private val sweepAngle = 360f / colors.size
    private var buttonClicked = -1

    init {
        paint.style = Paint.Style.STROKE
        paint.color = Color.GRAY
        paint.strokeWidth = 5f
        paintC.style = Paint.Style.FILL
        paintC.color = Color.RED
    }

    override fun onDraw(canvas: Canvas) {
        super.onDraw(canvas)
        drawCircleButton(canvas)
    }

    private fun drawCircleButton(canvas: Canvas) {
        val centerX = width / 2f
        val centerY = width / 2f
        val radius = width.coerceAtMost(height) / 2f

        for (i in colors.indices) {
            paintC.color = if (i == buttonClicked)
                Color.GRAY
            else colors[i]
            canvas.drawArc(
                centerX - radius,
                centerY - radius,
                centerX + radius,
                centerY + radius,
                startAngle + i * sweepAngle,
                sweepAngle,
                true,
                paintC
            )
        }
    }

    override fun onTouchEvent(event: MotionEvent): Boolean {
        val centerX = width / 2f
        val centerY = width / 2f
        val x = event.x
        val y = event.y

        when (event.action) {
            MotionEvent.ACTION_DOWN -> {
                if (x < centerX && y < centerY){
                    buttonClicked = 0
                }
                if (x > centerX && y < centerY){
                    buttonClicked = 1
                }
                invalidate()
            }

            MotionEvent.ACTION_UP -> {
                buttonClicked = -1
                invalidate()
            }

        }
        return true
    }
}