simple-email/app/src/main/res/layout/fragment_messages.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout 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"
    tools:context=".ActivityView">

    <TextView
        android:id="@+id/tvNoEmail"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/title_no_messages"
        android:textAppearance="@style/TextAppearance.AppCompat.Medium"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/rvFolder"
        android:layout_width="0dp"
        android:layout_height="0dp"
        android:scrollbarStyle="outsideOverlay"
        android:scrollbars="vertical"
        app:layout_constraintBottom_toTopOf="@+id/bottom_navigation"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <com.google.android.material.bottomnavigation.BottomNavigationView
        android:id="@+id/bottom_navigation"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginTop="3dp"
        android:background="@color/colorPrimary"
        android:visibility="gone"
        app:itemIconTint="@color/bottomnav_background"
        app:itemTextColor="@color/bottomnav_background"
        app:labelVisibilityMode="labeled"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:menu="@menu/action_list_bottom" />

    <ProgressBar
        android:id="@+id/pbWait"
        style="@style/Base.Widget.AppCompat.ProgressBar"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:indeterminate="true"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <com.google.android.material.floatingactionbutton.FloatingActionButton
        android:id="@+id/fab"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="end|bottom"
        android:layout_margin="16dp"
        android:src="@drawable/baseline_edit_24"
        android:tint="@color/colorActionForeground"
        app:backgroundTint="?attr/colorAccent"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent" />

    <androidx.constraintlayout.widget.Group
        android:id="@+id/grpReady"
        android:layout_width="0dp"
        android:layout_height="0dp"
        app:constraint_referenced_ids="rvFolder" />
</androidx.constraintlayout.widget.ConstraintLayout>