Create base custom view

BlurSurfaceView_01.kt

class BlurSurfaceView: View {
    private var canvas: Canvas? = null
    private lateinit var bitmap: Bitmap

    constructor(context: Context) : super(context)

    constructor(context: Context, attrs: AttributeSet?) : super(context, attrs)

    override fun onSizeChanged(w: Int, h: Int, oldw: Int, oldh: Int) {
        super.onSizeChanged(w, h, oldw, oldh)
        init(measuredWidth, measuredHeight)
    }

    private fun init(measuredWidth: Int, measuredHeight: Int) {
        bitmap = Bitmap.createBitmap(
            measuredWidth,
            measuredHeight,
            Bitmap.Config.ARGB_8888
        )
        canvas = Canvas(bitmap)
    }

    override fun onDraw(canvas: Canvas) {
        super.onDraw(canvas)
        canvas.save()
        canvas.drawBitmap(bitmap, 0f, 0f, null)
        canvas.restore()
    }
}