chooseThemeDialogWithDark.kt

  private fun chooseThemeDialog() {

        val builder = AlertDialog.Builder(this)
        builder.setTitle(getString(R.string.choose_theme_text))
        val styles = arrayOf("Light","Dark","System default")
        val checkedItem = 0

        builder.setSingleChoiceItems(styles, checkedItem) { dialog, which ->

            when (which) {
                0 -> {
                    AppCompatDelegate.setDefaultNightMode(AppCompatDelegate.MODE_NIGHT_NO)
                    delegate.applyDayNight()
                    dialog.dismiss()
                }
                1 -> {
                    AppCompatDelegate.setDefaultNightMode(AppCompatDelegate.MODE_NIGHT_YES)
                    delegate.applyDayNight()

                    dialog.dismiss()
                }
                2 -> {
                    AppCompatDelegate.setDefaultNightMode(AppCompatDelegate.MODE_NIGHT_FOLLOW_SYSTEM)
                    delegate.applyDayNight()
                    dialog.dismiss()
                }

            }
        }

        val dialog = builder.create()
        dialog.show()
    }