Activity quickly flashes white before switching to dark / night theme

I've implemented a Dark / night mode switch in my App I copied the implementation from the Google I/O App.

I've created a ThemedActivityDelegate that can be included in ViewModels. The actual changing to light or dark is done using the Extension function: updateForTheme.

But I see the SettingsActivity briefly flashing white before it turns black. While I put the updateForTheme method before setContentView.

MainActivity:

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

    binding = DataBindingUtil.setContentView(this, R.layout.activity_main)
    viewModel = ViewModelProvider(this, viewModelFactory).get(MainViewModel::class.java)
    updateForTheme(viewModel.currentTheme)

    lifecycleScope.launch {
        lifecycle.repeatOnLifecycle(Lifecycle.State.STARTED) {
            launch {
                viewModel.theme.collect { theme ->
                    updateForTheme(theme)
                }
            }
        }
    }
}

Extensions.kt:

fun AppCompatActivity.updateForTheme(theme: Theme) = when (theme) {
    Theme.DARK -> delegate.localNightMode = AppCompatDelegate.MODE_NIGHT_YES
    Theme.LIGHT -> delegate.localNightMode = AppCompatDelegate.MODE_NIGHT_NO
    Theme.SYSTEM -> delegate.localNightMode = AppCompatDelegate.MODE_NIGHT_FOLLOW_SYSTEM
    Theme.BATTERY_SAVER -> delegate.localNightMode = AppCompatDelegate.MODE_NIGHT_AUTO_BATTERY
}

SettingsActivity:

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    updateForTheme(Theme.DARK)
    setContentView(R.layout.activity_settings)
}

from Activity quickly flashes white before switching to dark / night theme