fragment_settings.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">

        <!--<Preference
            android:iconSpaceReserved="false"
            android:key="user"
            android:persistent="false"
            android:selectable="false"
            android:title="@string/title_user_settings" />
        <EditTextPreference
            android:icon="@drawable/ic_user_name"
            android:inputType="textPersonName"
            android:key="@string/key_user_name"
            android:title="@string/user_name"
            app:singleLineTitle="true" />
    <PreferenceCategory/>-->

        <Preference
            android:iconSpaceReserved="false"
            android:key="app"
            android:persistent="false"
            android:selectable="false"
            android:title="@string/title_app_settings"
            />

        <ListPreference
            android:defaultValue="@string/en_value"
            android:entries="@array/language_list"
            android:entryValues="@array/language_list_values"
            android:icon="@drawable/ic_language"
            android:key="@string/key_language"
            android:title="@string/lang"

        />
        <SwitchPreference
            android:defaultValue="true"
            android:icon="@drawable/ic_notifications_sound"
            android:key="@string/key_sound"
            android:summaryOff="@string/summary_off"
            android:summaryOn="@string/summary_on"
            android:title="@string/title_sound" />

    <SwitchPreference
        android:defaultValue="false"
        android:icon="@drawable/ic_theme"
        android:key="@string/key_dark_theme"
        android:summaryOff="@string/summary_off_theme"
        android:summaryOn="@string/summary_on_theme"
        android:title="@string/title_theme" />

</PreferenceScreen>