A scalable ZXing QR code drawable, which supports tint and transparency. Unlike a 515x515 bitmap commonly used in Android QR guides, the drawable is always sharp.

BitMatrixDrawable.kt

import android.content.res.ColorStateList
import android.graphics.Canvas
import android.graphics.Color
import android.graphics.ColorFilter
import android.graphics.Paint
import android.graphics.PixelFormat
import android.graphics.RectF
import android.graphics.drawable.Drawable
import androidx.annotation.ColorInt
import com.google.zxing.common.BitMatrix

class BitMatrixDrawable(
    private val bitMatrix: BitMatrix,
    @ColorInt
    squareColor: Int = Color.BLACK,
) : Drawable() {
    private val defaultSquareColor = squareColor
    private val squarePaint = Paint().apply {
        color = squareColor

        // Stroke is to compensate for float rounding.
        style = Paint.Style.FILL_AND_STROKE
        strokeWidth = 1f
    }

    private var squareWidth: Float = 1f
    private var squareHeight: Float = 1f

    override fun setBounds(left: Int, top: Int, right: Int, bottom: Int) {
        super.setBounds(left, top, right, bottom)
        squareWidth = (right - left).toFloat() / bitMatrix.width
        squareHeight = (bottom - top).toFloat() / bitMatrix.height
    }

    override fun draw(canvas: Canvas) {
        (0 until bitMatrix.width).forEach { x ->
            (0 until bitMatrix.height).forEach { y ->
                if (bitMatrix[x, y]) {
                    val left = x * squareWidth
                    val top = y * squareHeight
                    canvas.drawRect(
                        RectF(
                            left,
                            top,
                            left + squareWidth,
                            top + squareHeight
                        ),
                        squarePaint
                    )
                }
            }
        }
    }

    override fun setAlpha(alpha: Int) {
        squarePaint.alpha = alpha
    }

    override fun setColorFilter(colorFilter: ColorFilter?) {
        squarePaint.colorFilter = colorFilter
    }

    override fun setTintList(tint: ColorStateList?) {
        if (tint != null) {
            squarePaint.color = tint.defaultColor
        } else {
            squarePaint.color = defaultSquareColor
        }
        invalidateSelf()
    }

    override fun getOpacity(): Int = PixelFormat.TRANSLUCENT
}

QrDrawableFactory.kt

import android.graphics.Color
import androidx.annotation.ColorInt
import androidx.core.graphics.drawable.TintAwareDrawable
import com.google.zxing.BarcodeFormat
import com.google.zxing.EncodeHintType
import com.google.zxing.qrcode.QRCodeWriter
import com.google.zxing.qrcode.decoder.ErrorCorrectionLevel

class QrDrawableFactory {
    private val writer = QRCodeWriter()

    suspend fun getDrawable(
        content: String,
        @ColorInt
        squareColor: Int = Color.BLACK,
        errorCorrectionLevel: ErrorCorrectionLevel = ErrorCorrectionLevel.M,
        margin: Int = 0,
    ) = writer.encode(
        content,
        BarcodeFormat.QR_CODE,
        // 1x1 matrix yields the minimum size matrix for the data size.
        1, 1,
        mapOf(
            EncodeHintType.ERROR_CORRECTION to errorCorrectionLevel,
            EncodeHintType.MARGIN to margin,
        )
    ).let { bitMatrix ->
        checkNotNull(bitMatrix)

        BitMatrixDrawable(
            bitMatrix = bitMatrix,
            squareColor = squareColor,
        )
    }
}