activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/activity_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.darshanbshah.odsystem.MainActivity">

    <Button
        android:text="Sign Out"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/sign_out_button"
        android:onClick="signOut"
        style="@android:style/Widget.Material.Button.ButtonBar.AlertDialog"
        android:layout_alignParentTop="true"
        android:layout_alignParentEnd="true" />
</RelativeLayout>