packages/SystemUI/res/layout/inattentive_sleep_warning.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.
  -->

<FrameLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/sleep_warning_dialog_container"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:theme="@android:style/Theme.Material.Dialog"
    android:focusable="true">
    <View
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:background="@android:color/black"
        android:alpha="?android:backgroundDimAmount" />
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="@drawable/rounded_bg_full"
        android:layout_margin="8dp"
        android:padding="16dp"
        android:layout_gravity="top"
        android:orientation="vertical">
        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/inattentive_sleep_warning_title"
            android:layout_marginBottom="8dp"
            android:textColor="?android:attr/textColorPrimary"
            android:textAppearance="@android:style/TextAppearance.Material.Large"/>

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/inattentive_sleep_warning_message"
            android:textColor="?android:attr/textColorSecondary"
            android:textAppearance="@android:style/TextAppearance.Material"/>
    </LinearLayout>
</FrameLayout>