xdz-app/app/src/main/res/layout/fragment_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"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <!-- 底部导航栏 -->
    <com.google.android.material.bottomnavigation.BottomNavigationView
        android:id="@+id/bottomNavView"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="?android:attr/windowBackground"
        app:itemIconTint="@android:color/black"
        app:itemTextColor="@android:color/black"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:menu="@menu/bottom_navigation_menu" />

</androidx.constraintlayout.widget.ConstraintLayout>