portrait-layout

<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"
    android:orientation="vertical">

    <TextView
        android:id="@+id/textview"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:gravity="center"
        android:textAppearance="@style/TextAppearance.MaterialComponents.Headline6"
        android:textColor="?colorPrimary"
        app:layout_constraintBottom_toTopOf="@id/bottom_bar"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        tools:text="@string/bottom_nav_label" />

    <com.google.android.material.bottomnavigation.BottomNavigationView
        android:id="@+id/bottom_bar"
        style="@style/Widget.MaterialComponents.BottomNavigationView.PrimarySurface"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:menu="@menu/nav_menu" />

</androidx.constraintlayout.widget.ConstraintLayout>