Hiding App bar in a particular fragment with Navigation UI

If you are using navigation UI in your application , if you want to hide your app bar (top bar of your app showing navigation icon)  or back navigation arrow in a particular fragment you can do like this in your Mainactivity

class MainActivity : AppCompatActivity() {
  class MainActivity : AppCompatActivity() {
  private lateinit var drawerlayout : DrawerLayout
    private lateinit var navView : NavigationView
    override fun onCreate(savedInstanceState: Bundle?) {

        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        drawerlayout = findViewById(R.id.drawer_layout)
        navView = findViewById(R.id.nav_view)
        val navController : NavController = this.findNavController(R.id.navhost)
        NavigationUI.setupActionBarWithNavController(this,navController,drawerlayout)
        NavigationUI.setupWithNavController(navView,navController)
        navController.addOnDestinationChangedListener { _, destination, _ ->  
            if(destination.id==R.id.qaFragment){
                supportActionBar?.hide()
            }
            else{
                supportActionBar?.show()
            }
        }
    }

    override fun onSupportNavigateUp(): Boolean {
        val navController : NavController = findNavController(R.id.navhost)
        return NavigationUI.navigateUp(navController,drawerlayout)
    }
}

In the main activity you have to use OnDestinationChangeListener, in the listener you have to check for destination  fragment for which you want to hide the actionBar and hide it.

navController.addOnDestinationChangedListener { _, destination, _ ->  
            if(destination.id==R.id.qaFragment){
                supportActionBar?.hide()
            }
            else{
                supportActionBar?.show()
            }
        }