class MainActivity : AppCompatActivity(), BottomNavigationView.OnNavigationItemSelectedListener {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        loadFragment(new HomeFragment())

        BottomNavigationView navigation = findViewById(R.id.navigation)
        navigation.setOnNavigationItemSelectedListener(this)
    }

    ...

    fun onNavigationItemSelected(item: MenuItem?): Boolean {
        fragment: Fragment = null
        return true
    }
}

override