samples-flatfoot/PersistenceSample/app/src/main/res/layout/product_fragment.xml

<?xml version="1.0" encoding="utf-8"?>
<!--
  ~ Copyright 2017, The Android Open Source Project
  ~
  ~ Licensed under the Apache License, Version 2.0 (the "License");
  ~ you may not use this file except in compliance with the License.
  ~ You may obtain a copy of the License at
  ~
  ~      http://www.apache.org/licenses/LICENSE-2.0
  ~
  ~ Unless required by applicable law or agreed to in writing, software
  ~ distributed under the License is distributed on an "AS IS" BASIS,
  ~ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  ~ See the License for the specific language governing permissions and
  ~ limitations under the License.
  -->

<layout xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:app="http://schemas.android.com/apk/res-auto">

    <data>

        <import type="android.view.View"/>

        <variable
            name="isLoading"
            type="boolean" />

        <variable
            name="productViewModel"
            type="com.example.android.persistence.viewmodel.ProductViewModel"/>
    </data>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:background="@color/cardview_light_background"
        android:orientation="vertical">

        <include
            layout="@layout/product_item"
            app:product="@{productViewModel.product}"/>

        <FrameLayout
            android:layout_width="match_parent"
            android:layout_height="match_parent">

            <TextView
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:id="@+id/loading_comments_tv"
                android:text="@string/loading_comments"
                app:visibleGone="@{isLoading}"/>

            <FrameLayout
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:id="@+id/comments_list_wrapper">

                <android.support.v7.widget.RecyclerView
                    android:id="@+id/comment_list"
                    android:contentDescription="@string/cd_comments_list"
                    android:layout_width="match_parent"
                    android:layout_height="match_parent"
                    app:layoutManager="LinearLayoutManager"
                    app:visibleGone="@{!isLoading}"/>
            </FrameLayout>
        </FrameLayout>


    </LinearLayout>
</layout>