res/values/attrs.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <declare-styleable name="KeyboardView">
        <attr name="keyBackground" format="reference"/>
        <attr name="keyTextSize" format="dimension"/>
        <attr name="keyTextColorPrimary" format="color"/>
        <attr name="keyTextColorSecondary" format="color"/>
        <attr name="labelTextSize" format="dimension"/>
        <attr name="fontFamily" format="string" />
        <attr name="textStyle" format="enum">
            <enum name="normal" value="0" />
            <enum name="bold" value="1" />
            <enum name="italic" value="2" />
            <enum name="bold_italic" value="3" />
        </attr>
    </declare-styleable>
</resources>