How to use a SwitchPreference to create a setting for light/night mode

Question

For my app I am using SharedPreferences to create a setting that allows the user to switch between light and dark theme when using it. My problem is every time I load up the app and turn on the setting nothing happens and how to make my app switch between light and dark theme using a SwitchPreference using multiple activities.

For context I am building an app that is connected to Firestore that allows users to add TV show data from the Recycler View list.

I have tried looking for documentation on Google and watching videos online to see if I can find any similarity to my issue, but every time I do there is like 50 different ways of doing so.

This is my activity for the RecyclerView List and some of the SharedPreferences:

    override fun onResume(){
        super.onResume()
        
        val sharedPreferences = getSharedPreferences("MyPrefs", Context.MODE_PRIVATE)
        val editor = sharedPreferences.edit()
        val isDarkTheme = sharedPreferences.getBoolean("night",false)

        if (!isDarkTheme) {
            AppCompatDelegate.setDefaultNightMode(AppCompatDelegate.MODE_NIGHT_NO)
            editor.putBoolean("night",false)
            editor.apply()
        } else {
            AppCompatDelegate.setDefaultNightMode(AppCompatDelegate.MODE_NIGHT_YES)
            editor.putBoolean("night",true)
            editor.apply()
        }

        recyclerViewTV = findViewById(R.id.recyclerViewShows)
        recyclerViewTV.layoutManager = LinearLayoutManager(this)
        data = ArrayList<TV>()

        tvAdapter = TVAdapter(data)
        recyclerViewTV.adapter = tvAdapter

        db = FirebaseFirestore.getInstance()

        db.collection("ProjectTVShows")
            .get()
            .addOnSuccessListener { result ->
                for (document in result) {
                    var show = document.getString("name")
                    var direct = document.getString("director")
                    var view = document.getString("viewership")
                    data.add(TV(show, direct, view))

                    Log.d("MY DEBUG", "${document.id} => ${document.data}")
                    Log.d("MY DEBUG", "show => $show")
                    Log.d("MY DEBUG", "direct => $direct")
                    Log.d("MY DEBUG", "view => $view")
                }
                tvAdapter.notifyDataSetChanged()
            }
            .addOnFailureListener { exception ->
                Log.w("MY DEBUG", "Error getting documents.", exception)
            }
    }

    override fun onCreateOptionsMenu(menu: Menu?): Boolean {
        val inflater = menuInflater
        inflater.inflate(R.menu.toolmenu, menu)

        return true
    }

    override fun onOptionsItemSelected(item: MenuItem): Boolean {
        return when (item.getItemId()) {
            R.id.add_shows-> {
                val intent = Intent(this@TVShowListActivity, AddShowActivity::class.java)
                startActivity(intent)
                true
            }

            R.id.settings->{
                val intent = Intent(this@TVShowListActivity, SettingsActivity::class.java)
                startActivity(intent)
                true
            }

            else -> super.onOptionsItemSelected(item)
        }
    }}

This is my UserPreferenceFragment:

class UserPreferenceFragment: PreferenceFragmentCompat() {
    override fun onCreatePreferences(savedInstanceState: Bundle?, rootKey: String?) {
        setPreferencesFromResource(R.xml.preferences, rootKey)
    }
}

This is my preference layout for the light/dark mode setting

This is my preference layout in xml:

<?xml version="1.0" encoding="utf-8"?>
<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto">

    <SwitchPreferenceCompat
        app:defaultValue="false"
        app:key="night"
        app:summary="Toggle between light and dark mode"
        app:title="@string/light_settings" />
</PreferenceScreen>