A background drawbale with rounded corners and shadow effect around it

BackgroundDrawable.kt

import android.graphics.*
import android.graphics.drawable.Drawable

class BackgroundDrawable : Drawable() {

    private val shadowSize = 3f.dp
    private val rectRadius = 5f.dp

    private val rect = RectF()

    private val paint = Paint(Paint.ANTI_ALIAS_FLAG).apply {
        style = Paint.Style.FILL
        setShadowLayer(
            shadowSize,
            0f,
            0f,
            Color.LTGRAY
        )
    }

    var backgroundColor = Color.TRANSPARENT
        set(value) {
            field = value
            invalidateSelf()
        }

    override fun onBoundsChange(bounds: Rect) {
        rect.apply {
            left = shadowSize
            top = shadowSize
            right = bounds.right - shadowSize
            bottom = bounds.bottom - shadowSize
        }
        invalidateSelf()
    }

    override fun draw(canvas: Canvas) {
        paint.color = backgroundColor
        canvas.drawRoundRect(
            rect,
            rectRadius,
            rectRadius,
            paint
        )
    }

    override fun setAlpha(alpha: Int) {
        
    }

    override fun setColorFilter(colorFilter: ColorFilter?) {
        
    }

    override fun getOpacity(): Int {
        return PixelFormat.TRANSLUCENT
    }
    
}