app/src/main/res/values/attr.xml

<?xml version="1.0" encoding="utf-8"?>

<resources>
    <declare-styleable name="CircularImageView">
        <attr name="border" format="boolean"/>
        <attr name="border_width" format="dimension"/>
        <attr name="border_color" format="color"/>
        <attr name="shadow" format="boolean"/>
    </declare-styleable>
</resources>