activity_settings.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".SettingsActivity">

    <TextView
        android:id="@+id/settingTitle"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Settings"
        android:layout_centerHorizontal="true"
        style="@style/HeaderStyle"
        />

    <Button
        android:id="@+id/mode"
        android:layout_height="wrap_content"
        android:layout_width="match_parent"
        android:text="Switch to Dark Mode"
        style="@style/BtnStyle"
        android:layout_below="@id/settingTitle"
        app:cornerRadius="0dp"
        android:layout_marginTop="50dp"/>

    <Button
        android:id="@+id/exit"
        android:layout_height="wrap_content"
        android:layout_width="match_parent"
        android:text="Exit"
        style="@style/BtnStyle"
        android:layout_below="@id/mode"
        app:cornerRadius="0dp"/>
</RelativeLayout>