Getting deprecated warning while getting the height, width in android for Api >= 30 and Api < 30 even after enclosing the code in if else block

After going through some stack overflow questions, I have written the code to get the height and width in Android for Api level >= 30 and Api level < 30 below :

class MainActivity : AppCompatActivity() {

        override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        val backgroundThread = Thread {

        val metric: WindowMetrics
        val insets: Insets    // An Insets instance holds four integer offsets which describe changes to the four edges of a Rectangle.
        val displayMetrics: DisplayMetrics
        val width: Int
        val height: Int
        val insetsWidth: Int
        val insetsHeight: Int

        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.R) {

            // Code for API level 30 and higher

            metric = windowManager.currentWindowMetrics
            insets = windowManager.currentWindowMetrics.windowInsets.getInsetsIgnoringVisibility (WindowInsets.Type.navigationBars() or WindowInsets.Type.displayCutout ())

            insetsWidth = insets.right + insets.left
            insetsHeight = insets.top + insets.bottom

            Log.d ("tally", "${insets.right}, ${insets.left}, ${insets.top}, ${insets.bottom}")

            width = metric.bounds.width () - insetsWidth
            height = metric.bounds.height () - insetsHeight

        } else {

            displayMetrics = DisplayMetrics ()
            windowManager.defaultDisplay.getMetrics (displayMetrics)

            width = displayMetrics.widthPixels
            height = displayMetrics.heightPixels
        }
    }
    backgroundThread.start()
}

/**
 * A native method that is implemented by the 'dpi_poc' native library,
 * which is packaged with this application.
 */
external fun stringFromJNI(): String

companion object {
    // Used to load the 'dpi_poc' library on application startup.
    init {
        System.loadLibrary("dpi_poc")
    }
}

}

I'm not able to understand why I'm still getting the deprecated warning, as shown in the image below, even after enclosing the code in if else block.

What's wrong in the above code and how to solve this warning and write code to get the height and width in android for both api level >= 30 and api level < 30?