tests/DiagnosticTools/res/layout/diagnostic_tools.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
  -->

<LinearLayout
  xmlns:android="http://schemas.android.com/apk/res/android"
  xmlns:app="http://schemas.android.com/apk/res-auto"
  xmlns:tools="http://schemas.android.com/tools"
  android:layout_width="match_parent"
  android:layout_height="match_parent"
  android:orientation="vertical">

  <Toolbar
    android:id="@+id/toolbar"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:background="?android:attr/colorPrimary"
    android:elevation="4dp"
    android:theme="@android:attr/actionBarTheme"/>

  <FrameLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <androidx.recyclerview.widget.RecyclerView
      android:id="@+id/my_recycler_view"
      android:layout_width="match_parent"
      android:layout_height="match_parent"
      android:scrollbars="vertical"/>
    <com.google.android.material.floatingactionbutton.FloatingActionButton
      android:id="@+id/floatingActionButton"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:clickable="true"
      android:layout_gravity="bottom|end"
      android:layout_margin="16dp"
      android:src="@drawable/ic_delete_sweep_black_24dp"
      android:onClick="onClickActionButton"/>
  </FrameLayout>


</LinearLayout>