wulkanowy-mod/app/src/main/res/layout/activity_main.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_container"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <com.google.android.material.appbar.AppBarLayout
        android:id="@+id/main_app_bar"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:fitsSystemWindows="true"
        app:layout_constraintBaseline_toTopOf="parent">

        <com.google.android.material.appbar.MaterialToolbar
            android:id="@+id/main_toolbar"
            android:layout_width="match_parent"
            android:layout_height="?attr/actionBarSize" />
    </com.google.android.material.appbar.AppBarLayout>

    <androidx.fragment.app.FragmentContainerView
        android:id="@+id/main_fragment_container"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        app:layout_constraintBottom_toTopOf="@id/main_bottom_nav"
        app:layout_constraintTop_toBottomOf="@id/main_app_bar"
        tools:layout="@layout/fragment_dashboard" />

    <androidx.coordinatorlayout.widget.CoordinatorLayout
        android:id="@+id/main_message_container"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        app:layout_constraintBottom_toTopOf="@id/main_bottom_nav" />

    <com.google.android.material.bottomnavigation.BottomNavigationView
        android:id="@+id/main_bottom_nav"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        app:itemTextAppearanceActive="@style/WulkanowyTheme.TextAppearanceBottomNavigation"
        app:itemTextAppearanceInactive="@style/WulkanowyTheme.TextAppearanceBottomNavigation"
        app:labelVisibilityMode="labeled"
        app:layout_constraintBottom_toBottomOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>