BarcodeView.kt

import android.content.Context
import android.util.AttributeSet
import android.view.View
import android.graphics.*
import android.graphics.PorterDuff
import android.graphics.PorterDuffXfermode


class BarcodeView @JvmOverloads constructor(
    context: Context, attrs: AttributeSet? = null, defStyleAttr: Int = 0
) : View(context, attrs, defStyleAttr) {


    private val backgroundColor = 0xA4000000
    private val edgeColor = 0xA400FF00
    private val rectSize = 300

    private var centerX = 0
    private var centerY = 0


    override fun onDraw(canvas: Canvas) {
        super.onDraw(canvas)
        centerX = width / 2
        centerY = height / 2

        setLayerType(LAYER_TYPE_SOFTWARE, null)

        drawBackgroud(canvas)
        drawTransparentRect(canvas)
        drawEdges(canvas)
    }

    private fun drawBackgroud(canvas: Canvas) {
        val paint = Paint(Paint.ANTI_ALIAS_FLAG)
        paint.style = Paint.Style.FILL
        paint.color = backgroundColor.toInt()

        canvas.drawPaint(paint)

    }

    private fun drawTransparentRect(canvas: Canvas) {
        val rect = RectF()

        rect.bottom = (centerY - rectSize).toFloat()
        rect.top = (centerY + rectSize).toFloat()
        rect.right = (centerX + rectSize).toFloat()
        rect.left = (centerX - rectSize).toFloat()

        val paint = Paint(Paint.ANTI_ALIAS_FLAG)
        paint.xfermode = PorterDuffXfermode(PorterDuff.Mode.CLEAR)
        paint.alpha = 0;
        paint.isAntiAlias = true

        canvas.drawRect(rect, paint)
    }

    private fun drawEdges(canvas: Canvas) {
        val paint = Paint(Paint.ANTI_ALIAS_FLAG)
        paint.style = Paint.Style.STROKE
        paint.strokeWidth = 10f
        paint.color = edgeColor.toInt()


        val left = (centerX - rectSize).toFloat()
        val right = (centerX + rectSize).toFloat()
        val bottom = (centerY + rectSize).toFloat()
        val top = (centerY - rectSize).toFloat()

        val edgeSize = left/2

        canvas.drawLine(left, bottom, left + edgeSize, bottom, paint)// left horizontal top
        canvas.drawLine(left, top, left + edgeSize, top, paint)// left horizontal bottom

        canvas.drawLine(right, bottom, right - edgeSize, bottom, paint)// right horizontal bottom
        canvas.drawLine(right, top, right - edgeSize, top, paint)// right horizontal bottom

        canvas.drawLine(left, bottom, left , bottom - edgeSize, paint)// left horizontal bottom
        canvas.drawLine(left, top, left , top + edgeSize, paint)// left horizontal bottom

        canvas.drawLine(right, bottom, right , bottom - edgeSize, paint )// left horizontal bottom
        canvas.drawLine(right, top, right, top + edgeSize, paint)// left horizontal bottom

    }
}

layout.xml

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout
        xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:app="http://schemas.android.com/apk/res-auto"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

    <ImageView
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:src="@drawable/bg"
            android:scaleType="centerCrop"/>

    <com.android.example.BarcodeView
            android:layout_width="match_parent"
            android:layout_height="match_parent"/>

</FrameLayout>