Other than the NavController, I am getting the same error for AppCompatActivity(), layoutInflater, and a few more in the below mentioned code.

Error: Unresolved reference: NavController and so on...

MY Code:

package com.example.wordsapp

import android.os.Bundle
import androidx.appcompat.app.AppCompatActivity
import androidx.navigation.NavController
import androidx.navigation.NavHost
import androidx.navigation.ui.setupActionBarWithNavController
import com.example.wordsapp.databinding.ActivityMainBinding

/**
 * Main Activity and entry point for the app. Displays a RecyclerView of letters.
 */
class MainActivity : AppCompatActivity() {
    private lateinit var navController: NavController
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        val binding = ActivityMainBinding.inflate(layoutInflater)
        setContentView(binding.root)

        val navHostFragment = supportFragmentManager.findFragmentById(R.id.nav_host_fragment) as NavHost
        navController = navHostFragment.navController
        setupActionBarWithNavController(navController)
    }

    override fun onSupportNavigateUp(): Boolean {
        return navController.navigateUp() || super.onSupportNavigateUp()
    }
}

CodePudding user response：

1. First check if you can build the project.

if the project can be built, then it may be a Kotlin/JVM mismatch. But if you find a build error, consider checking your dependencies.

if the above solution does not fix the error, try to close android studio completely and then restart it.

CodePudding user response：

To add to Dron's answer - if none of that works you can also try File > invalidate cache's and restart