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kotlinlang

Hey guys! So, I have been trying out Navigation Components. Created an activity with 2 fragments. A goes to B on button press and B has a button to go back to A by destroying current fragment.

Now the issue is on this B to A fragment. If I use

```        binding.button2.setOnClickListener {
            activity?.supportFragmentManager?.popBackStack()
        }```
On going back to A, if I use A to B button again, app will crash with this message:
`java.lang.IllegalArgumentException: navigation destination dev.theimpulson.myapplication:id/action_firstFragment_to_secondFragment is unknown to this NavController`

However, if I use this in B to A button:
```        binding.button2.setOnClickListener {
            activity?.onBackPressed()
        }```
App doesn't crashes anymore. Any ideas why?

You normally don't interact with the fragment manager yourself when navigating

use `findNavController.navigate(id)` For back/up actions override `onSupportNavigateUp()` in your hosting activity

you provide the navcontroller with an `AppbarConfiguration`, this sets your toplevel destinations. Other fragments then get a 'back' arrow in the actionbar to go back. No manual popping of the backstack needed.