folio_activity.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:id="@+id/main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.folioreader.ui.activity.FolioActivity"
    tools:menu="@menu/menu_main">

    <com.folioreader.ui.view.DirectionalViewpager
        android:id="@+id/folioPageViewPager"
        android:layout_width="0dp"
        android:layout_height="0dp"
        app:direction="vertical"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <com.folioreader.ui.view.FolioAppBarLayout
        android:id="@+id/appBarLayout"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        android:animateLayoutChanges="true">

        <androidx.appcompat.widget.Toolbar
            android:id="@+id/toolbar"
            android:layout_width="match_parent"
            android:layout_height="?android:attr/actionBarSize"
            app:contentInsetLeft="0dp"
            app:contentInsetStart="0dp"
            app:contentInsetStartWithNavigation="0dp" />

    </com.folioreader.ui.view.FolioAppBarLayout>

</androidx.constraintlayout.widget.ConstraintLayout>