A semitransparent view with a rounded corner hole in it

OverlayView.kt

class OverlayWithHoleImageView(context: Context?, attrs: AttributeSet?) : androidx.appcompat.widget.AppCompatImageView(context, attrs) {
    private var rect: RectF? = null
    private val paint = Paint(Paint.ANTI_ALIAS_FLAG).apply {
        color = Color.parseColor("#a8000000")
        style = Paint.Style.FILL
    }
    private val addMode = PorterDuffXfermode(PorterDuff.Mode.ADD)
    private val clearMode = PorterDuffXfermode(PorterDuff.Mode.CLEAR)
    private val radius = 40.dp
    private val margin = 32.dp

    override fun onSizeChanged(w: Int, h: Int, oldw: Int, oldh: Int) {
        super.onSizeChanged(w, h, oldw, oldh)
        rect = RectF(
            margin + paddingLeft,
            margin + paddingTop,
            w - margin - paddingRight,
            h - margin - paddingBottom
        )
    }

    override fun onDraw(canvas: Canvas) {
        super.onDraw(canvas)
        rect?.let {
            paint.xfermode = addMode
            canvas.drawPaint(paint)
            paint.xfermode = clearMode
            canvas.drawRoundRect(it, radius, radius, paint)
        }
    }

    init {
        setLayerType(View.LAYER_TYPE_HARDWARE, null)
    }
}