item_checkbox.xml

<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto">
    <data>
        <variable
            name="toppings"
            type="com.jephtecolin.model.Topping[]" />
        <variable
            name="listener"
            type="com.jephtecolin.kwii.ui.custom.OnCheckedChangeListener" />
        <variable
            name="viewModel"
            type="com.jephtecolin.kwii.ui.consumable_detail.ConsumableDetailViewModel" />
    </data>

 <com.jephtecolin.kwii.ui.custom.CheckBoxGroup
     android:id="@+id/gp"
     android:layout_width="match_parent"
     android:layout_height="wrap_content"
     app:totalPrice="@={viewModel.totalCost}"
     setOnCheckedChangeListener="@{listener}"
     setItems="@{toppings}"/>
</layout>