Using PreferenceFragment to effortlessly handle user settings https://blog.jakelee.co.uk/using-preferencefragment-to-effortlessly-handle-user-settings/

MainActivity.kt

class MainActivity: AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        this.supportFragmentManager
            .beginTransaction()
            .replace(R.id.fragment_frame, PrefsFragment())
            .commit()
    }
}

preferences.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <!-- Booleans -->
    <string name="pref_boolean1">boolean1</string>
    <bool name="pref_boolean1_default">false</bool>
    <string name="boolean1_title">First boolean</string>
    <string name="boolean1_desc">This toggles the first boolean</string>

    <string name="pref_boolean2">boolean2</string>
    <bool name="pref_boolean2_default">false</bool>
    <string name="boolean2_title">Second boolean</string>
    <string name="boolean2_desc">This toggles the second boolean</string>

    <!-- Strings -->
    <string name="pref_string1">string1</string>
    <string name="pref_string1_default">FirstDefault</string>
    <string name="string1_title">String 1</string>
    <string name="string1_desc">Set the first string</string>

    <string name="pref_string2">string2</string>
    <string name="pref_string2_default">SecondDefault</string>
    <string name="string2_title">String 2</string>
    <string name="string2_desc">Set the second string</string>

    <!-- Int -->
    <string name="pref_int1">int1</string>
    <integer name="pref_int1_step">1</integer>
    <integer name="pref_int1_min">0</integer>
    <integer name="pref_int1_max">10</integer>
    <integer name="pref_int1_default">10</integer>
    <string name="int1_title">Int 1</string>
    <string name="int1_desc">The first integer</string>

    <string name="pref_int2">int2</string>
    <integer name="pref_int2_step">1</integer>
    <integer name="pref_int2_min">0</integer>
    <integer name="pref_int2_max">10</integer>
    <integer name="pref_int2_default">2</integer>
    <string name="int2_title">Int 2</string>
    <string name="int2_desc">The second integer</string>
</resources>

preferences_ui.xml

<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android">
    <Preference
            android:key="@string/pref_show_values"
            android:title="@string/show_values_title"
            android:icon="@drawable/ic_show_values"
            android:summary="@string/show_values_desc"/>
    <PreferenceScreen
            android:title="@string/open_repo_title"
            android:icon="@drawable/ic_repo"
            android:summary="@string/open_repo_desc">
        <intent android:action="android.intent.action.VIEW"
                android:data="@string/repo_url"/>
    </PreferenceScreen>
    <PreferenceCategory android:title="Booleans">
        <SwitchPreference
                android:key="@string/pref_boolean1"
                android:defaultValue="@bool/pref_boolean1_default"
                android:title="@string/boolean1_title"
                android:icon="@drawable/ic_one"
                android:summary="@string/boolean1_desc"/>
        <SwitchPreference
                android:key="@string/pref_boolean2"
                android:defaultValue="@bool/pref_boolean2_default"
                android:title="@string/boolean2_title"
                android:icon="@drawable/ic_two"
                android:dependency="@string/pref_boolean1"
                android:summary="@string/boolean2_desc"/>
    </PreferenceCategory>
    <PreferenceCategory android:title="Strings">
        <EditTextPreference
                android:key="@string/pref_string1"
                android:defaultValue="@string/pref_string1_default"
                android:title="@string/string1_title"
                android:icon="@drawable/ic_one"
                android:summary="@string/string1_desc"/>
        <EditTextPreference
                android:key="@string/pref_string2"
                android:defaultValue="@string/pref_string2_default"
                android:title="@string/string2_title"
                android:icon="@drawable/ic_two"
                android:summary="@string/string2_desc"/>
    </PreferenceCategory>
    <PreferenceCategory android:title="Integers">
        <SeekBarPreference
                android:key="@string/pref_int1"
                android:defaultValue="@integer/pref_int1_default"
                android:title="@string/int1_title"
                android:icon="@drawable/ic_one"
                android:summary="@string/int1_desc"/>
        <SeekBarPreference
                android:key="@string/pref_int2"
                android:defaultValue="@integer/pref_int2_default"
                android:title="@string/int2_title"
                android:icon="@drawable/ic_two"
                android:summary="@string/int2_desc"/>
    </PreferenceCategory>
</PreferenceScreen>

PrefsFragment.kt

class PrefsFragment : PreferenceFragmentCompat(), SharedPreferences.OnSharedPreferenceChangeListener {

    override fun onCreatePreferences(savedInstanceState: Bundle?, rootKey: String?) {
        addPreferencesFromResource(R.xml.preferences_ui)
        findPreference(getString(R.string.pref_show_values)).onPreferenceClickListener = showValuesListener
        setupSeekbars()
    }

    private fun setupSeekbars() {
        (findPreference(getString(R.string.pref_int1)) as SeekBarPreference).apply { 
            seekBarIncrement = resources.getInteger(R.integer.pref_int1_step)
            min = resources.getInteger(R.integer.pref_int1_min)
            max = resources.getInteger(R.integer.pref_int1_max)
        }

        (findPreference(getString(R.string.pref_int2)) as SeekBarPreference).apply {
            seekBarIncrement = resources.getInteger(R.integer.pref_int2_step)
            min = resources.getInteger(R.integer.pref_int2_min)
            max = resources.getInteger(R.integer.pref_int2_max)
        }
    }

    override fun onResume() {
        super.onResume()
        preferenceScreen.sharedPreferences.registerOnSharedPreferenceChangeListener(this)
    }

    override fun onPause() {
        super.onPause()
        preferenceScreen.sharedPreferences.unregisterOnSharedPreferenceChangeListener(this)
    }

    override fun onSharedPreferenceChanged(sharedPreferences: SharedPreferences, key: String) {
        when (key) {
            getString(R.string.pref_string1) -> {
                val pref = findPreference(key) as EditTextPreference
                Toast.makeText(activity!!, "String changed to ${pref.text}", Toast.LENGTH_SHORT).show()
            }
        }
    }

    private val showValuesListener = Preference.OnPreferenceClickListener { _ ->
        val prefHelper = PreferenceHelper(activity!!)
        AlertDialog.Builder(activity!!)
            .setTitle(R.string.values_title)
            .setMessage(String.format(getString(R.string.values_text),
                prefHelper.getBooleanPref(PreferenceHelper.BooleanPref.setting1),
                prefHelper.getBooleanPref(PreferenceHelper.BooleanPref.setting2),
                prefHelper.getStringPref(PreferenceHelper.StringPref.setting1),
                prefHelper.getStringPref(PreferenceHelper.StringPref.setting2),
                prefHelper.getIntPref(PreferenceHelper.IntPref.setting1),
                prefHelper.getIntPref(PreferenceHelper.IntPref.setting2)
                ))
            .setPositiveButton(R.string.values_close) { _, _ -> }
            .show()
        true
    }
}