res/layout/headsup_container.xml

<?xml version="1.0" encoding="utf-8"?>
<!--
    Copyright (C) 2019 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.
-->

<androidx.constraintlayout.widget.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:id="@+id/notification_headsup"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <androidx.constraintlayout.widget.Guideline
        android:id="@+id/gradient_edge"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="horizontal"
        app:layout_constraintGuide_begin="@dimen/headsup_scrim_height"/>

    <!-- Include a FocusParkingView at the beginning or end. The rotary controller "parks" the
         focus here when the user navigates to another window. This is also used to prevent
         wrap-around which is why it must be first or last in Tab order. -->
    <com.android.car.ui.FocusParkingView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintTop_toTopOf="parent"/>

    <View
        android:id="@+id/scrim"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:background="@drawable/headsup_scrim"
        app:layout_constraintBottom_toBottomOf="@+id/gradient_edge"
        app:layout_constraintTop_toTopOf="parent"/>

    <FrameLayout
        android:id="@+id/headsup_content"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="@dimen/headsup_notification_top_margin"
        app:layout_constraintEnd_toStartOf="parent"
        app:layout_constraintStart_toEndOf="parent"
        app:layout_constraintTop_toTopOf="parent"
    />

</androidx.constraintlayout.widget.ConstraintLayout>