how can i change the top bar while working with navigation?

1. override onCreateOptionsMenu() in MainActivity.

    override fun onCreateOptionsMenu(menu: Menu?): Boolean {
        super.onCreateOptionsMenu(menu)
        menuInflater.inflate(R.menu.menu_second, menu)
        return true
    }
   

2. create menus in res folder

   <menu xmlns:android="http://schemas.android.com/apk/res/android"
       xmlns:app="http://schemas.android.com/apk/res-auto">
       <item android:id="@+id/menu_next"
           android:title="toNext"
           android:titleCondensed="next"
           android:orderInCategory="1"
           android:icon="your icon"
           app:showAsAction="always" />
   </menu> 
   

menu api