Android Studio – Bottom Navigation Bar in Android Studio not Working?

        bottomNavigationView.setOnNavigationItemSelectedListener{
            when (it.itemId){

                R.id.local1 -> make_Fragment(fragment1)
                R.id.local2-> make_Fragment(fragment2)
                R.id.local3 -> make_Fragment(fragment3)
            }
            true

     }

Here bottomNavigationView is throwing error : Unresolved reference: bottomNavigationView and also i defined the id on mainactivity.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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=".main.MainActivity">


<FrameLayout
    android:id="@+id/fl_wapper"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_above="@id/bottomNavigationView"/>

    <com.google.android.material.bottomnavigation.BottomNavigationView
        android:id="@+id/bottomNavigationView"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        app:menu="@menu/bottom_nav"
        />


</RelativeLayout>

Here bottomNavigationView shows error and also when(it.itemId){
the bottomNavigationView is the id of the bottom bar.i also tried clean project and rebuild project.

tell me a solution to resolve this problem?