In the <Conditional Navigation> section of the Nav...

# android

[Florian]

In the Conditional Navigation section of the Navigation Component, each fragment handles what happens when the user presses back on the login screen by observing a LOGIN_SUCCESSFUL flag:

class ProfileFragment : Fragment() {
    ...

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        val navController = findNavController()

        val currentBackStackEntry = navController.currentBackStackEntry!!
        val savedStateHandle = currentBackStackEntry.savedStateHandle
        savedStateHandle.getLiveData<Boolean>(LoginFragment.LOGIN_SUCCESSFUL)
                .observe(currentBackStackEntry, Observer { success ->
                    if (!success) {
                        val startDestination = navController.graph.startDestination
                        val navOptions = NavOptions.Builder()
                                .setPopUpTo(startDestination, true)
                                .build()
                        navController.navigate(startDestination, null, navOptions)
                    }
                })
    }

    ...
}

What is the benefit of this approach over the old approach from the codelab, where the LoginFragment just handles its back button itself:

requireActivity().onBackPressedDispatcher.addCallback(viewLifecycleOwner) {
   navController.popBackStack(R.id.mainFragment, false)
}

The second approach seems much simpler and less repetitive