View to add a semitransparent overlay with a fully transparent square cutout

SquareCutoutOverlay.kt

import android.content.Context
import android.graphics.*
import android.util.AttributeSet
import android.view.View
import kotlin.math.max
import kotlin.math.min


class SquareCutoutOverlay(
    context: Context,
    attrs: AttributeSet? = null,
    defStyleAttr: Int = 0
) : View(context, attrs, defStyleAttr) {

  constructor(context: Context): this(context, null, 0)
  constructor(context: Context, attrs: AttributeSet?): this(context, attrs, 0)

  private val semitransparentColor = Color.parseColor("#A6000000")

  private val transparentPaint = Paint().apply {
    color = Color.TRANSPARENT
    strokeWidth = 10f
  }

  private val semitransparentPaint = Paint().apply {
    color = Color.TRANSPARENT
    strokeWidth = 10f
  }
  
  val path = Path()

  init {

  }

  override fun onDrawForeground(canvas: Canvas) {
    super.onDrawForeground(canvas)

    val cornerRadii = 40f
    val padding = 120f
    val heightWidth = min(canvas.width, canvas.height) - padding*2
    val horizontalAdjust = (canvas.width - heightWidth)/2 //Distance between screen edge and square horizontally
    val verticalAdjust = (canvas.height - heightWidth)/2 //Distance between screen edge and square vertically

    val barcodeSquare = RectF(
        padding,
        verticalAdjust,
        horizontalAdjust + heightWidth,
        verticalAdjust + heightWidth
    )

    path.apply {
      reset()
      addRoundRect(barcodeSquare, cornerRadii, cornerRadii, Path.Direction.CW)
      fillType = Path.FillType.INVERSE_EVEN_ODD
    }

    canvas.apply {
      drawRoundRect(barcodeSquare, cornerRadii, cornerRadii, transparentPaint)

      drawPath(path, semitransparentPaint)
      clipPath(path)
      drawColor(semitransparentColor)
    }
  }
}