MainActivity.kt

import android.os.Bundle
import androidx.appcompat.app.AppCompatActivity
import androidx.navigation.NavController
import androidx.navigation.fragment.NavHostFragment
import androidx.navigation.ui.setupActionBarWithNavController

class MainActivity : AppCompatActivity() {
    private lateinit var navController: NavController

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)  // Set the content view to your activity_main layout

        // Initialize NavController from the NavHostFragment
        val navHostFragment = supportFragmentManager.findFragmentById(R.id.nav_host_fragment) as NavHostFragment
        navController = navHostFragment.navController

        // Setup the action bar to work with NavController
        setupActionBarWithNavController(navController)
    }

    override fun onSupportNavigateUp(): Boolean {
        // Handle navigation when the home or up button is pressed
        return navController.navigateUp() || super.onSupportNavigateUp()
    }
}