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android compose: remember failed with destructuring pattern

I'm trying to get specific behavior with focus and so use something like this :
val (focusA, focusB) = remember { FocusRequester.createRefs() }
And since i didn't get the correct behavior, start to investigate and the destructuring pattern with remember is the problem.
If you try this (this is what is it done under the hood of FocusRequester.createRefs()):
` class MyClass
object MyClassFactory{
operator fun component1() = MyClass()
operator fun component2() = MyClass()
}
fun createRefs() = MyClassFactory
#Composable
private fun ContentBody() {
val (a, b) = remember {
createRefs()
}
Log.d(">>:a", "${a.hashCode()}")
Log.d(">>:b", "${b.hashCode()}")
}
`
You will realise that a and b are new instance each time there is a recomposition.
Does any one have some information about that? Why remember fail with destructuring pattern. We can see many time this pattern (i use it with constraint layout for example), and according to that, it is a complete failure because each time a new instance are created...
What I'm doing wrong? I solved all my problem by using a remember without destructuring.
Thank.

Jetpack compose change in uiState doesn't trigger recomposition

I think I haven't quite wrapped my head around how compose states work yet. I'm not able to trigger a recomposition when an item in the uiState changes.
I'm building an app that need notification access, so for that I'm navigating the user to the settings and after the user has granted permission they have to navigate back to the app. That's where I want to trigger the recomposition.
I have the permission check in onResume working and the variable in the uiState changes, but the recomposition doesn't get called. What am I missing here?
Composable
#Composable
private fun MainLayout(viewModel: SetupViewModel){
val uiState = viewModel.uiState.collectAsState()
SetupItem(
title = "Notification access",
summary = if(uiState.value.hasNotificationPermission) stringResource(R.string.granted) else stringResource(R.string.not_granted){}
}
SetupUiState.kt
data class SetupUiState(
var hasNotificationPermission: Boolean = false
)
I know for a fact that hasNotificationPermission gets set to true, but the summary in the SetupItem does not update. How do I accomplish that?

The problem here is that the hasNotificationPermission field is mutable (var and not val). Compose is not tracking inner fields for change. You have two options here:
Modify the SetupUiState as a whole, assuming you are using StateFlow in your ViewModel, it can look like this:
fun setHasNotificationPermission(value: Boolean) {
uiState.update { it.copy(hasNotificationPermission = value) }
}
You should also change hasNotificationPermission from var to val.
You can make use of compose's State and do something like this:
class SetupUiState(
initialHasPermission: Boolean = false
) {
var hasNotificationPermission: Boolean by mutableStateOf(initialHasPermission)
}
With this you can then simply do uiState.hasNotificationPermission = value and composition will be notified, since it's tracking State instances automatically.

What/Where is the best way to handle with states on Jetpack Compose?

I've seen some Jetpack Compose projects and I've seen two types of managing states, not realizing which one is better.
For example, let's assume: the input state. I've seen people manage this state in the UI, using remember to save the state of the value.
Another way I've seen is to create this mutableState in the ViewModel and store/use it from there. What's the best way to do this?

In addition to #Thracian's answer.
Let me share my thought process based on my current level of experience in Jetpack Compose. Just a disclaimer, I'm still in the learning curve.
IMO, theres no such thing as "best", things in our field evolves, what might be considered "best" today may become obsolete tomorrow, but there are certain practices that are "recommended", approved and adopted by the community which might save you from dealing with some pitfalls (e.g unwanted re-compositions, infinite navhost calls( you already dealt with this) etc..), but its up to you if you will follow it or not.
So what your'e trying to understand is called State Hoisting. The way I could explain this is by just simply sampling a scenario (again this is based on my own experience with how I apply my knowledge in Jetpack Compose).
Consider a Login use-case with 3 different levels of complexity
A Login UI prototype : — Just showcasing your potential Login Screen design and user interaction
Login UI Mock-up : — With a bit of validation and some toast showing a negative scenario, just an advance version of the prototype
A fully working Login module — where you have to construct view models, bind things to lifecycles, perform concurrent operations etc..
At this point, you already have an idea the different levels of state management based on the use-case above.
For a Login prototype, I won't be needing a state class or a view model, since its just a prototype
#Composable
fun LoginScreen() {
val userName by remember { <mutable string state username> }
val password by remember { <mutable string state password> }
Column {
Text(text = username)
Text(text = password)
Button("Login")
}
}
and because its a very simple UI(composable), I only need to specify basic structure of a composable using remember + state, showcasing an input is happening.
For the Login mock-up with simple validation, we utilized the recommended state hoisting using a class,
class LoginState {
var event;
var mutableUserNameState;
var mutablePasswordState;
fun onUserNameInput() {...}
fun onPasswordInput() {...}
fun onValidate() {
if (not valid) {
event.emit(ShowToast("Not Valid"))
} else {
event.emit(ShowToast("Valid"))
}
}
}
#Composable
fun LoginScreen() {
val loginState by remember { LoginState }
LaunchedEffect() {
event.observe {
it.ShowToast()
}
}
Column {
Text(text = loginState.mutableUserNameState, onInput = { loginState.onUserNameInput()} )
Text(text = loginState.mutablePasswordState, onInput = { loginState.onPasswordInput()} )
Button(loginState.onValidate)
}
}
Now for a full blown Login Module, where your'e also taking lifecylce scopes into consideration
class LoginViewModel(
val userRepository: UserRepository // injected by your D.I framework
): ViewModel {
var event;
var mutableUserNameState;
var mutablePasswordState;
fun onUserNameInput() {...}
fun onPasswordInput() {...}
fun onValidateViaNetwork() {
// do a non-blocking call to a server
viewModelScope.launch {
var isUserValid = userRepository.validate(username, password)
if (isUserValid) {
event.emit(ShowToast("Valid"))
} else {
event.emit(ShowToast("Not Valid"))
}
}
}
}
#Composable
fun LoginScreen() {
val userNameState by viewModel.mutableUserNameState
val passwordState by viewModel.mutablePasswordState
LaunchedEffect() {
event.observe {
it.ShowToast()
}
}
Column {
Text(text = userNameState, onInput = { viewModel.onUserNameInput()} )
Text(text = passwordState, onInput = { viewModel.onPasswordInput()} )
Button(viewModel.onValidateViaNetwork)
}
}
Again, this is just based on my experience and how I decide on hoisting my states. As for the snippets I included, I tried to make them as pseudo as possible without making them look out of context so they are not compilable. Also mock and prototype are considered the same, I just used them in conjunction to put things into context.

It depends on your preference. Using states inside a Composable if you are building a standalone Composable or a library is preferred. Any class you see with rememberXState() keeps state variable. For instance scrollState()
#Composable
fun rememberScrollState(initial: Int = 0): ScrollState {
return rememberSaveable(saver = ScrollState.Saver) {
ScrollState(initial = initial)
}
}
#Stable
class ScrollState(initial: Int) : ScrollableState {
/**
* current scroll position value in pixels
*/
var value: Int by mutableStateOf(initial, structuralEqualityPolicy())
private set
// rest of the code
}
This is a common approach in Jetpack Compose. I use this approach in libraries i build, for instance in this image crop library, i keep state and Animatable. Animatable which is low level default animation class also has hold its own states.
#Suppress("NotCloseable")
class Animatable<T, V : AnimationVector>(
initialValue: T,
val typeConverter: TwoWayConverter<T, V>,
private val visibilityThreshold: T? = null
) {
internal val internalState = AnimationState(
typeConverter = typeConverter,
initialValue = initialValue
)
/**
* Current value of the animation.
*/
val value: T
get() = internalState.value
/**
* Velocity vector of the animation (in the form of [AnimationVector].
*/
val velocityVector: V
get() = internalState.velocityVector
/**
* Returns the velocity, converted from [velocityVector].
*/
val velocity: T
get() = typeConverter.convertFromVector(velocityVector)
/**
* Indicates whether the animation is running.
*/
var isRunning: Boolean by mutableStateOf(false)
private set
/**
* The target of the current animation. If the animation finishes un-interrupted, it will
* reach this target value.
*/
var targetValue: T by mutableStateOf(initialValue)
private set
}
and so on. This approach is doing for ui components that don't involve business logic but Ui logic.
When you need to update your Ui based on business logic like search or getting results from an API you should use a Presenter class which can be ViewModel too.
Last but least people are now questioning whether there should be a ViewModel with Jetpack Compose since we can use states with an AAC ViewModel. And cashapp introduced molecule library, you can check it out either.
Also this link about state holders is good source to read

How should I go about implementing MVVM architecture pattern in my project?

I know this is a very documented topic, but I couldn't find a way to implement it in my project, even after spending hours trying to figure it out.
My root problem is that I have a RecyclerView with an Adapter whose content isn't updating as I'd like. I'm a beginner in Android, so I didn't implement any MVVM or such architecture, and my project only contains a repository, fetching data from Firebase Database, and passing it to a list of ShowModel, a copy of said list being used in my Adapter to display my shows (In order to filter/sort them without modifying the list with all shows).
However, when adding a show to the database from another Activity, my Adapter isn't displaying the newly added show (as detailed here)
I was told to use LiveData and ViewModel, but even though I started understanding how it works after spending time researching it, I don't fully get how I should use it in order to implement it in my project.
Currently I have the following classes:
The Adapter:
class ShowAdapter(private val context: MainActivity, private val layoutId: Int, private val textNoResult: TextView?) : RecyclerView.Adapter<ShowAdapter.ViewHolder>(), Filterable {
var displayList = ArrayList(showList)
class ViewHolder(view : View) : RecyclerView.ViewHolder(view){
val showName: TextView = view.findViewById(R.id.show_name)
val showMenuIcon: ImageView = view.findViewById(R.id.menu_icon)
}
#SuppressLint("NewApi")
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
val view = LayoutInflater.from(parent.context).inflate(layoutId, parent, false)
return ViewHolder(view)
}
#SuppressLint("NewApi", "WeekBasedYear")
override fun onBindViewHolder(holder: ViewHolder, position: Int) {
val currentShow = displayList[position]
val index = holder.adapterPosition
holder.showName.text = currentShow.name
holder.itemView.setOnClickListener{ // Display show content
val intent = Intent(context, DetailsActivity::class.java)
intent.putExtra("position", index)
startActivity(context, intent, null)
}
holder.showMenuIcon.setOnClickListener{
val popupMenu = PopupMenu(context, it)
popupMenu.menuInflater.inflate(R.menu.show_management_menu, popupMenu.menu)
popupMenu.show()
popupMenu.setOnMenuItemClickListener {
when(it.itemId){
R.id.edit -> { // Edit show
val intent = Intent(context, AddShowActivity::class.java)
intent.putExtra("position", index)
startActivity(context, intent, null)
return#setOnMenuItemClickListener true
}
R.id.delete -> { // Delete show
val repo = ShowRepository()
repo.deleteShow(currentShow)
displayList.remove(currentShow)
notifyItemRemoved(index)
return#setOnMenuItemClickListener true
}
else -> false
}
}
}
}
override fun getItemCount(): Int = displayList.size
// Sorting/Filtering methods
}
The fragment displaying the adapter:
class HomeFragment : Fragment() {
private lateinit var context: MainActivity
private lateinit var verticalRecyclerView: RecyclerView
private lateinit var buttonAddShow: Button
private lateinit var showsAdapter: ShowAdapter
override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
val view = inflater.inflate(R.layout.fragment_home, container, false)
context = getContext() as MainActivity
buttonAddShow = view.findViewById(R.id.home_button_add_show)
buttonAddShow.setOnClickListener{ // Starts activity to add a show
startActivity(Intent(context, AddShowActivity::class.java))
}
verticalRecyclerView = view.findViewById(R.id.home_recycler_view)
showsAdapter = ShowAdapter(context, R.layout.item_show, null)
verticalRecyclerView.adapter = showsAdapter
return view
}
}
The MainActivity:
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
loadFragment(HomeFragment())
}
private fun loadFragment(fragment: Fragment){
val repo = ShowRepository()
if(showsListener != null) databaseRef.removeEventListener(showsListener!!)
repo.updateData{
val transaction = supportFragmentManager.beginTransaction()
transaction.replace(R.id.fragment_container, fragment)
transaction.addToBackStack(null)
if(supportFragmentManager.isStateSaved)transaction.commitAllowingStateLoss()
else transaction.commit()
}
}
}
The repository:
class ShowRepository {
object Singleton{
val databaseRef = FirebaseDatabase.getInstance().getReference("shows")
val showList = arrayListOf<ShowModel>()
var showsListener: ValueEventListener? = null
}
fun updateData(callback: () -> Unit){
showsListener = databaseRef.addValueEventListener(object : ValueEventListener {
override fun onDataChange(snapshot: DataSnapshot) {
showList.clear()
for(ds in snapshot.children){
val show = ds.getValue(ShowModel::class.java)
if(show != null) showList.add(show)
}
callback()
}
override fun onCancelled(p0: DatabaseError) { }
})
}
fun insertShow(show: ShowModel){
databaseRef.child(show.id).setValue(show)
}
fun deleteShow(show: ShowModel){
databaseRef.child(show.id).removeValue()
}
}
From what I understand of LiveData and ViewModel, what I should do is creating a ShowViewModel containing a MutableLiveData<List<ShowModel>> containing the shows, and then observe it in my HomeFragment and update the adapter depending on the changes happening. However, everytime I start something to implement it, I encounter a situation where I'm lost and don't know what I should do, which leads me back to square one once again. I've been trying this for more than a week without progressing even a little bit, and that's why I'm here, hoping for some insight.
Sorry for the silly question and the absurd amount of informations, and hoping someone will be able to help me understand what I do wrong/should do.

(this ended up longer than I meant it to be - hope it's not too much! There's a lot to learn, but you don't have to make it super complicated at first)
Broadly, working backwards, it should go like this:
Adapter
displays whatever the Fragment tells it to (some kind of setData function that updates its internal list and refreshes)
passes events to the Fragment (deleteItem(item), showDetails(item) etc.) - don't have the Adapter doing things like starting Activites, that's not its responsibility
Fragment
grabs a reference to any ViewModels (only certain components like Fragments and Activities can actually "own" them)
observes any LiveData (or collects Flows if you're doing it that way) on the VM, and updates stuff in the UI in response
e.g. model.shows.observe(viewLifecycleOwner) { shows -> adapter.setData(shows) }
handles UI events and calls methods on the VM in response, e.g. click listeners, events from the Adapter
ViewModel
acts as a go-between for the UI (the Fragment) and the data layer (the repository)
exposes methods for handling events like deleting items, interacts with the data layer as required (e.g. calling the appropriate delete function)
exposes data state for the UI to observe, so it can react to changes/updates (e.g. a LiveData containing the current list of shows that the data layer has provided)
That's the basic setup - the VM exposes data which the UI layer observes and reacts to, by displaying it. The UI layer also produces events (usually down to user interaction) which are passed to the VM. You can read more about this general approach in this guide about app architecture - it's worth reading because not only is it recommended as a way to build apps, a lot of the components you use in modern Android are designed with this kind of approach in mind (like the reactive model of wiring stuff up).
You could handle the Adapter events like this:
// in your Adapter
var itemDeletedListener: ((Item) -> Unit)? = null
// when the delete event happens for an item
itemDeletedListener?.invoke(item)
// in your Fragment
adapter.itemDeletedListener = { viewModel.deleteItem(it) }
which is easier than implementing an interface, and lets you wire up your Adapter similar to doing setOnClickListener on a button. Notice we're passing the actual Item object here instead of a list index - generally this is easier to work with, you don't need to maintain multiple copies of a list just so you can look up an index given to you by something else. Passing a unique ID can make sense though, especially if you're working with a database! But usually the object itself is more useful and consistent
The data layer is the tricky bit - the ViewModel needs to communicate with that to get the current state. Say you delete an item - you then need to get the current, updated list of shows. You have three approaches:
Call the delete function, immediately after fetch the current data, and set it on the appropriate LiveData
This can work, but it's not very reactive - you're doing one action, then immediately doing another because you know your data is stale. It would be better if the new data just arrived automatically and you could react to that by pushing it out. The other issue is that calling the delete function might not have an immediate effect - if you fetch the current data, nothing might have changed yet. It's better if the data layer is responsible for announcing updates.
This is the simplest approach though, and probably a good start! You could run this task in a coroutine (viewModelScope.launch { // delete and fetch and update LiveData }) so any slowness doesn't block the current thread.
Have the data layer's functions return the current, updated data that results
Similar to above, you're just sort of pushing the fetching into the data layer. This requires all those functions to be written to return the current state, which could take a while! And depending on what data you want, this might be impossible - if you have an active query on some data, how does the function know what specific data to return?
Make the ViewModel observe the data it wants, so when the data layer updates, you get the results automatically
This is the recommended reactive approach - again it's that two-way idea. The VM calling a function on the data layer is completely separate from the VM receiving new data. One thing just happens as a natural consequence of the other, they don't need to be tied together. You just need to wire them up right!
How do you actually do that though? If you're working with something like Room, that's already baked in. Queries can return async data providers like LiveData or Flows - your VM just needs to observe those and expose the results, or just expose them directly. That way, when a table is updated, any queries (like the current shows) push a new value, and the observers receive it and do whatever they need to do, like telling the Adapter to display the data. It all Just Works once it's wired up.
Since you have your own repo, you need to expose your own data sources. You could have a currentShows LiveData or (probably preferably) the flow equivalent, StateFlow. When the repo initialises, and when any data is changed, it updates that currentShows data. Anything observing that (e.g. the VM, the Fragment through a LiveData/Flow that the VM exposes) will automatically get the new values. So broadly:
// Repo
// this setup is exactly the same as your typical LiveData, except you need an initial value
private val _currentShows = MutableStateFlow<List<Show>>(emptyList()) // or whatever default
val currentShows: StateFlow<List<Show>> = _currentShows
fun deleteItem(item: Item) {
// do the deletion
// get the updated show list
_currentShows.value = updatedShowList
}
// ViewModel
// one way of doing things - you have a lot of options! This literally just exposes
// the state from the data layer, and turns it into a LiveData (if you want that)
val currentShows = repo.currentShows.asLiveData()
// Fragment
// wire things up so you handle new data as it arrives
viewModel.currentShows.observe(viewLifecycleOwner) { shows -> adapter.setData(shows) }
That's basically it. I've skimmed over a lot because honestly, there's a lot to learn with this - especially about Flows and coroutines if you're not already familiar with those. But hopefully that gives you an overview of the general idea, and don't be afraid to take shortcuts (like just updating your data in the ViewModel by setting its LiveData values) while you're learning and getting the hang of it. Definitely give that app architecture guide a read, and also the guides for ViewModels and LiveData. It'll start to click when you get the general idea!

How to refresh the UI of a fragment using LiveData after Firestore data loads

I'm making an Android app using Kotlin with Firebase products. I have successful connections with Firestore and can successfully retrieve the data I want, but I am having difficulty displaying it within a RecyclerView.
When the application loads, and after a user has logged in, my Firestore queries use the UID of the user to get a list of their assignments. Using logs I can see that this occurs without issue as the home screen loads. Within the home screen fragment I have data binding for the RecyclerView and setup my ViewModel to have the fragment observe the returned Firestore data.
I believe it is a misunderstanding on my part on exactly how LiveData works because if I tap the bottom nav icon for the home screen to trigger a refresh of the UI then the list populates and I can use the app as desired. Therefore my observer/LiveData must not be setup properly as it is not automatically refreshing once the data has changed (null list to not null list).
As I'm new to programming I'm sure I've fallen into a number of pitfalls and done a few things incorrectly, but I've been searching through StackOverflow and YouTube for help on this issue for months now. Unfortunately I don't have all of the links saved to every video and every post.
I've tried tweaking the ViewModel and the Repository/Database class (singleton) to different effects and currently I'm at my best version with only a single tap required to refresh the UI. Previously it took multiple taps.
from the Database class
private val assignments = MutableLiveData<List<AssignmentModel>>()
private fun getUserAssignments(c: ClassModel) {
val assignmentQuery = assignmentRef.whereEqualTo("Class_ID", c.Class_ID)
assignmentQuery.addSnapshotListener { documents, _ ->
documents?.forEach { document ->
val a = document.toObject(AssignmentModel::class.java)
a.Assignment_ID = document.id
a.Class_Title = c.Title
a.Formatted_Date_Due = formatAssignmentDueDate(a)
assignmentMap[a.Assignment_ID] = a
}
}
}
fun getAssignments() : LiveData<List<AssignmentModel>> {
assignments.value = assignmentMap.values.toList().filter {
if (it.Date_Due != null) it.Date_Due!!.toDate() >= Calendar.getInstance().time else true }
.sortedBy { it.Date_Due }
return assignments
}
from the ViewModel
class AssignmentListViewModel internal constructor(private val myDatabase: Database) : ViewModel() {
private var _assignments: LiveData<List<AssignmentModel>>? = null
fun getAssignments() : LiveData<List<AssignmentModel>> {
var liveData = _assignments
if (liveData == null) {
liveData = myDatabase.getAssignments()
_assignments = liveData
}
return liveData
}
}
from the Fragment
class AssignmentList : Fragment() {
private lateinit var model: AssignmentListViewModel
override fun onCreateView(
inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
val binding = AssignmentListBinding.inflate(inflater, container, false)
val factory = InjectorUtils.provideAssignmentListViewModelFactory()
model = ViewModelProvider(this, factory).get(AssignmentListViewModel::class.java)
val assignmentAdapter = AssignmentAdapter()
binding.assignmentRecycler.adapter = assignmentAdapter
updateUI(assignmentAdapter)
return binding.root
}
private fun updateUI(adapter: AssignmentAdapter) {
model.getAssignments().observe(this, Observer { assignments ->
if (assignments.isNotEmpty()) adapter.submitList(assignments)
})
}
}
Again, I expect the RecyclerView to populate automatically once the data from Firestore appears, but it doesn't. The screen remains empty until I tap the home screen button.
These snippets show the most recent changes I've made. Originally I had the Firestore query function returning the LiveData directly. I also had a much simpler ViewModel of something like fun getAssignments() = myDatabase.getAssignments().
Thanks for any and all help and advice.

When troubleshooting this issue, I'd recommend starting by looking at two things.
Take a look at where/when you're updating your LiveData
The goal is whenever the data in Firebase updates, your assignments LiveData updates your UI. Something like:
Firestore updates
Firestore triggers SnapshotListener
SnapshotListener updates LiveData
LiveData observer updates UI
So in your snapshot listener, you should be updating your LiveData, which is what I think you're missing. So it would be something like:
// Where you define your SnapshotListner
assignmentQuery.addSnapshotListener { documents, _ ->
// Process the data
documents?.forEach { document ->
val a = document.toObject(AssignmentModel::class.java)
a.Assignment_ID = document.id
a.Class_Title = c.Title
a.Formatted_Date_Due = formatAssignmentDueDate(a)
assignmentMap[a.Assignment_ID] = a
}
// Update your LiveData
assignments.value = assignmentMap.values.toList().filter {
if (it.Date_Due != null) it.Date_Due!!.toDate() >= Calendar.getInstance().time else true }
.sortedBy { it.Date_Due }
}
Now every time your Firestore updates, your LiveData will update and your UI should update.
Given the code change, getAssignments() can just return assignments. You can do this using a Kotlin backing property, covered here:
private val _assignments = MutableLiveData<List<AssignmentModel>>()
val assignments: LiveData<List<AssignmentModel>>
get() = _assignments
As for why it's not working at the moment, right now you call getAssignments() once on start up. This will filter an empty assignmentMap.values (I believe - might be worth checking), because when it's called, Firebase hasn't finished getting you any data. And when Firebase does get it's new data, it triggers the listener, but you don't update the LiveData.
Mind where you're setting up your listeners/observers
A tricky thing with LiveData observers and Firebase listeners is to make sure you only set them up once.
For your Firebase listener, you should be setting up the listener when you initialize your database and not every single time you call getUserAssignments. Then you wouldn't need all the null checking in the ViewModel, which essentially ensures that at least the ViewModel won't call getUserAssignments twice....but if you have other classes interacting with your database, they might call getUserAssignments multiple times and then you have tons of extra listeners.
Also, make sure you detach your listener.
One way to handle this is described in Doug Stevenson's talk Firebase and Android Jetpack: Fit Like a Glove - the talk includes a demo code here. The part that's related to this is how he handles LiveData -- notice how the class includes adding and removing the listener. The TL;DR is that he's using LiveData's lifecycle awareness to automatically do Firebase listener setup and cleanup. How that's done is a bit complicated, so I'd suggest watching the talk from here.
For your LiveData, setup/tear down looks correct since it's getting setup in onCreateView (and torn down automatically via the fact it's lifecycle aware). I might rename updateUI to something like setupUIObservation, since updateUI sounds like something you call multiple times. As with the Firebase listeners, you want to make sure you're not setting up the same LiveData observer more than once.
Hope that helps!