问如何从活动更新导航标题中的TextView？

EN

class User(val username: String, val display_name: String )

class MainActivity : AppCompatActivity() {


    private lateinit var appBarConfiguration: AppBarConfiguration
    private lateinit var mDrawerLayout: DrawerLayout
    private lateinit var btnLogout: TextView
    val client: OkHttpClient = OkHttpClient()


    fun getMyProfile(){
        // code that makes the request to my API is here!(and it's working)

            override fun onResponse(call: Call, response: Response) {
                val body= response.body()?.string()

                println(response.code())
                println(body)
                if(response.code()==200){
                    val gson = GsonBuilder().create()
                    val my_user = gson.fromJson(body, User::class.java)
                    val view = LayoutInflater.from(this@MainActivity).inflate(R.layout.nav_header_main, null, false)
                    val username: TextView = view.findViewById(R.id.username)
                    val display_name: TextView = view.findViewById(R.id.displayname)
                    username.text = my_user.username
                    display_name.text = my_user.display_name


                }
                if(response.code()==401){
                    // if the request is not allowed
                }
            }
        })
    }

    override fun onCreate(savedInstanceState: Bundle?) {



        val context:Context = baseContext
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        val toolbar: Toolbar = findViewById(R.id.toolbar)
        setSupportActionBar(toolbar)

        val fab: FloatingActionButton = findViewById(R.id.fab)
        fab.setOnClickListener { view ->
            Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                .setAction("Action", null).show()
        }
        val drawerLayout: DrawerLayout = findViewById(R.id.drawer_layout)
        val navView: NavigationView = findViewById(R.id.nav_view)
        val navController = findNavController(R.id.nav_host_fragment)
        // Passing each menu ID as a set of Ids because each
        // menu should be considered as top level destinations.
        appBarConfiguration = AppBarConfiguration(
            setOf(
                R.id.nav_home, R.id.nav_new_group, R.id.nav_new_channel,
                R.id.nav_contacts, R.id.nav_settings, R.id.nav_send
            ), drawerLayout
        )
        setupActionBarWithNavController(navController, appBarConfiguration)
        getMyProfile()
        ...
    }
        ...





}

<TextView
        android:id="@+id/displayname"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:paddingTop="@dimen/nav_header_vertical_spacing"
        android:text="@string/nav_header_title"
        android:textAppearance="@style/TextAppearance.AppCompat.Body1" />

    <TextView
        android:id="@+id/username"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/nav_header_subtitle" />