i want to use BottomNavigationView in my app and i'm facing this problem with kotlin (never had it before with java) i see this message :
classifier 'listFragment' does not have a companion object and thus must be initialized here

this is my code :

```
private val mOnNavigationItemSelectedListener = BottomNavigationView.OnNavigationItemSelectedListener { item ->
    when (item.itemId) {
        R.id.listNav -> {
//the problem is here in listFragment word below
            setFragment(listFragment)
            return@OnNavigationItemSelectedListener true
        }
        R.id.accountNav -> {
//the problem is here also in accountFragment word below
            setFragment(accountFragment)
            return@OnNavigationItemSelectedListener true
        }
false 
}
private fun setFragment(fragment: Fragment) {
    supportFragmentManager.beginTransaction().replace(R.id.mainFrame , fragment).commit()
}

```

any help is appreciated :)