Custom attributes in styles.xml

layout_button.xml

<Button
    android:layout_width="wrap_content"
    android:layout_height="?attr/defaultButtonHeight"
    android:text="Button"
    android:textColor="?attr/defaultButtonColor"
    />

values->attrs.xml

<resources> 
    ...
    <attr name="defaultButtonColor" format="reference" />
    <attr name="defaultButtonHeight" format="reference"/>
</resources>

values->colors.xml

<resources>
    ...
    <color name="red">#f00</color>
</resources>

values->dimens.xml

<resources>
    ...
    <dimen name="dp_100">100dp</dimen>
</resources>

values->styles.xml

<style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">
    ...
    <item name="defaultButtonColor">@color/red</item>
    <item name="defaultButtonHeight">@dimen/dp_100</item>
</style>