Hide android bottom navigation view for child screens/ fragments

Update (Navigation component 1.0)

As of Navigation component 1.0.0-alpha08, method addOnNavigatedListener(controller: NavController, destination: NavDestination) was changed to addOnDestinationChangedListener(controller: NavController, destination: NavDestination, arguments: Bundle). Its behavior was also slightly changed (it is also called if the destinations arguments change).

Old Answer

You can use NavController.OnNavigatedListener to achieve this behavior (set it in Activity onCreate):

findNavController(R.id.container).addOnNavigatedListener { _, destination ->
    when (destination.id) {
        R.id.dashboardFragment -> showBottomNavigation()
        else -> hideBottomNavigation()
    }
}

private fun hideBottomNavigation() {
    // bottom_navigation is BottomNavigationView
    with(bottom_navigation) {
        if (visibility == View.VISIBLE && alpha == 1f) {
            animate()
                    .alpha(0f)
                    .withEndAction { visibility = View.GONE }
                    .duration = EXIT_DURATION
        }
    }
}

private fun showBottomNavigation() {
    // bottom_navigation is BottomNavigationView
    with(bottom_navigation) {
        visibility = View.VISIBLE
        animate()
                .alpha(1f)
                .duration = ENTER_DURATION
    }
}

Using addOnDestinationChangedListener works, and it's the solution recommended in the official documentation, but it does cause some flickering, as the callback is executed before the fragment is attached.

I find the below answer more flexible, and handles animations better:

supportFragmentManager.registerFragmentLifecycleCallbacks(object : FragmentManager.FragmentLifecycleCallbacks() {
        override fun onFragmentViewCreated(fm: FragmentManager, f: Fragment, v: View, savedInstanceState: Bundle?) {
            TransitionManager.beginDelayedTransition(binding.root, Slide(Gravity.BOTTOM).excludeTarget(R.id.nav_host_fragment, true))
            when (f) {
                is ModalFragment -> {
                    binding.bottomNavigation.visibility = View.GONE
                }
                else -> {
                    binding.bottomNavigation.visibility = View.VISIBLE
                }
            }
        }
    }, true)

You can customize it depending on the transitions between your fragments, by choosing different animation (on my example it's a Slide), or by making the call at another lifecycle callback.

You have to make a method in MainActivity for visibility. Do call that method from fragments where you want to show or hide.

One thing I faced with such scenario is, bottom navigation visibility is not being properly gone. So I put bottom navigation view in Relative layout and hide that parent view.