How to hide a view in a fragment while using navigation component

Question

I have tried virtually all the answers found in:

but it doesn't work well:

I have a single activity:

activity_main.xml

  <androidx.fragment.app.FragmentContainerView
       android:id="@+id/nav_host_fragment"
       android:name="androidx.navigation.fragment.NavHostFragment"
       android:layout_width="0dp"
       android:layout_height="0dp"
       app:layout_constraintLeft_toLeftOf="parent"
       app:layout_constraintRight_toRightOf="parent"
       app:layout_constraintTop_toTopOf="parent"
       app:layout_constraintBottom_toBottomOf="parent"
       app:defaultNavHost="true"
       app:navGraph="@navigation/nav_graph" >
   </androidx.fragment.app.FragmentContainerView>

 <androidx.constraintlayout.widget.ConstraintLayout
      android:id="@+id/bottom_controls"
      android:layout_width="match_parent"
      android:layout_height="72dp"
      android:onClick="onSongInfoClick"
      android:background="@drawable/lyt_rounded_bottom_music"
      android:paddingStart="10dp"
      android:paddingEnd="10dp"
      android:elevation="25dp"
      app:layout_constraintTop_toBottomOf="@id/nav_host_fragment">

So, Inside the nav_graph, The start destination is a ViewPagerFragment consisting of various tabs.

Now, my first destination in the ViewPager is - SongsFragment

When I click the bottom_controls view from activity_main I am navigating to SongDetailsFragment like this:

MainActivity.kt

//on click song details
fun onSongInfoClick(v: View) {
    val navController = findNavController(R.id.nav_host_fragment)
    navController.navigateUp() // to clear previous navigation history
    navController.navigate(R.id.songDetailsFragment)
}

Here is what I want:

When in SongDetailsFragment:

Hide the bottom_controls in activity_main

When in other places:

Show the bottom_controls in activity_main

Right now: This is the current behaviour.

It works for the first time, but on subsequent trial, it doesn't work, as you can see:

The first time I clicked the bottom_controls, it was hidden in the songDetailsFragment (as it should), but subsequently it shows when in songDetailsFragment.

Here is how I am hiding/showing the bottom_control view:

In MainActivity.kt

songDetailViewModel.currentData.observe(this) {
    if (it.id !in arrayOf(0L, -1L, -2L)) {
        if (getCurrentVisibleFragment(this) == null){
           viewModel.showMiniPlayer()
            } else viewModel.hideMiniPlayer()
          } else viewModel.hideMiniPlayer()
       }

In SongDetailsFragment.kt

class SongDetailsFragment : BaseSongDetailFragment() {
  .....
}

BaseSongDetailsFragment.kt

open class BaseSongDetailFragment : Fragment() {

private val songDetailViewModel by sharedViewModel<SongDetailViewModel>()
protected val mainViewModel by inject<MainViewModel>()


override fun onActivityCreated(savedInstanceState: Bundle?) {
    super.onActivityCreated(savedInstanceState)
    showHideBottomSheet()
}

override fun onPause() {
    showHideBottomSheet()
    super.onPause()
}
override fun onResume() {
    showHideBottomSheet()
    super.onResume()
}
private fun showHideBottomSheet() {
    val currentData = songDetailViewModel.currentData.value ?: return
    if (currentData.id == 0L) return
    if (GeneralUtility.getCurrentVisibleFragment(requireActivity()) == SongDetailsFragment()){
        mainViewModel.hideMiniPlayer()
    }
    else{
        mainViewModel.showMiniPlayer()
    }
  } 
}

And finally, this is the getCurrentVisibleFragment() function

 //check if song details fragment
 fun getCurrentVisibleFragment(activity: Activity): SongDetailsFragment? { 
    val navHostFragment = (activity as FragmentActivity).supportFragmentManager.primaryNavigationFragment as NavHostFragment
    val fragmentManager: FragmentManager = navHostFragment.childFragmentManager
    val songDetailsFragment: Fragment? = fragmentManager.primaryNavigationFragment
    return if (songDetailsFragment is SongDetailsFragment) {
        songDetailsFragment as SongDetailsFragment
    } else null
}

score 1 · Accepted Answer · answered Aug 21 '21 at 14:42

I suspect this line:

GeneralUtility.getCurrentVisibleFragment(requireActivity()) == SongDetailsFragment()

with SongDetailsFragment() you always create a new instance of the fragment, then compare it with your current one. I would be surprised if this comparison returned true in any case. Try:

GeneralUtility.getCurrentVisibleFragment(requireActivity()) == this as SongDetailsFragment

How to hide a view in a fragment while using navigation component

1 Answers1