I'm fairly new to Kotlin/Android development, and am trying to figure out the best way to update data in a Room database. After following some tutorials, I currently have an architecture that looks like this:
Room Database with tables and DAOs -> Repository -> ViewModel -> Activity
So the activity has a ViewModel that calls the Repository, which in turn updates the database.
The ViewModel for the activity has a LiveData list of the object (there's also a factory to create the ViewModel, but that's just to allow the bookId to be passed in):
class ViewBookViewModel(application: Application, bookId: Int) : AndroidViewModel(application) {
private val repository: AppRepository
internal val flashCards: LiveData<List<FlashCard>>
init {
val flashCardDao = AppDatabase.getDatabase(application, viewModelScope).flashCardDao()
val bookDao = AppDatabase.getDatabase(application, viewModelScope).bookDao()
repository = AppRepository(flashCardDao, bookDao)
flashCards = flashCardDao.getByBookId(bookId)
}
fun insert(flashCard: FlashCard) = viewModelScope.launch(Dispatchers.IO){
repository.insert(flashCard)
}
fun setIsFavorited(cardUid: Long, favorited: Boolean) = viewModelScope.launch(Dispatchers.IO) {
repository.setIsFavorited(cardUid, favorited)
}
}
//The actual query that gets called eventually
#Query("UPDATE flashcard SET is_favorited = :favorited WHERE uid LIKE :cardUid")
fun setFavorited(cardUid: Long, favorited: Boolean)
And the Activity sets up the viewModel and also creates an observer on the
class ViewBookActivity : AppCompatActivity() {
private lateinit var flashCards: LiveData<List<FlashCard>>
private var layoutManager: RecyclerView.LayoutManager? = null
private lateinit var viewModel: ViewBookViewModel
private var bookId: Int = 0
private lateinit var bookTitle: String
override fun onCreate(savedInstanceState: Bundle?) {
...
bookId = intent.extras["bookId"] as Int
bookTitle = intent.extras["bookTitle"].toString()
layoutManager = LinearLayoutManager(this)
flashCardRecyclerView.layoutManager = layoutManager
viewModel = ViewModelProviders.of(this, ViewBookViewModelFactory(application, bookId as Int)).get(ViewBookViewModel::class.java)
flashCards = viewModel.flashCards
flashCards.observe(this, Observer { flashCards:List<FlashCard> ->
flashCardRecyclerView.adapter = FlashCardRecyclerAdapter(flashCards, viewModel)
})
}
}
Finally, I have a custom RecyclerAdapter, which is where I'm running into trouble. I have it set up so that when the user taps the "favorite" button on the Flash Card, it updates the database. However, this also causes the Activity to "refresh", scrolling to the top. I assume this is because it is observing LiveData, and that data is being changed.
custom RecylcerAdapter with ViewHolder code (stripped not-relevant code):
class FlashCardRecyclerAdapter(val flashCards: List<FlashCard>, val viewModel: ViewBookViewModel) : RecyclerView.Adapter<FlashCardRecyclerAdapter.FlashCardViewHolder>() {
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): FlashCardViewHolder {
val v: View = LayoutInflater
.from(parent.context)
.inflate(R.layout.flash_card, parent, false)
return FlashCardViewHolder(v)
}
override fun onBindViewHolder(holder: FlashCardViewHolder, position: Int) {
val card = flashCards[position]
holder.isFavorited = card.isFavorited
holder.uid = card.uid
holder.modifyFavoriteButtonImage(holder.isFavorited)
}
override fun getItemCount(): Int {
return flashCards.size
}
inner class FlashCardViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView){
var mFavorited: Button
var frontShowing: Boolean
var isFavorited: Boolean = false
var uid: Long = 0
init {
mFavorited = itemView.findViewById(R.id.favoriteButton)
mFavorited.setOnClickListener { _ ->
isFavorited = !isFavorited
viewModel.setIsFavorited(uid, isFavorited) // Here is the database call
modifyFavoriteButtonImage(isFavorited)
}
}
fun modifyFavoriteButtonImage(isFavorited: Boolean){
// Code removed, just updates the image to be a filled/empty star based on favorited status
}
}
I feel like I am probably doing something wrong, as passing the ViewModel into the recylcer adapter in order to update the DB does not seem correct. Is there a pattern I should be using for this sort of situation, or should I change the code to not be using LiveData? Any help would be greatly appreciated.
flashCards.observe(this, Observer { flashCards:List<FlashCard> ->
flashCardRecyclerView.adapter = FlashCardRecyclerAdapter(flashCards, viewModel)
}
you should not be making a new adapter instance here, instead, assign the values you get from the live data to the existing adapter (adapter.flashCards = flashCards, LiveData value) and call adapter.notifyDataSetChanged, this will tell your adapter that new data came in and it needs to update.
you should not be passing your ViewModel to your adapter (or anything).
you can do something like this instead:
class FlashCardRecyclerAdapter(val flashCards: List<FlashCard>, val callback:(FlashCard) -> Unit)
then, where you declare your adapter, you do this :
val adapter = FlashCardRecyclerAdapter(...) {
viewModel.update(it)
}
and then :
override fun onBindViewHolder(holder: FlashCardViewHolder, position: Int) {
val card = flashCards[position]
holder.isFavorited = card.isFavorited
holder.uid = card.uid
holder.itemView.setOnClickListener {
callback.invoke(card)
}
holder.modifyFavoriteButtonImage(holder.isFavorited)
}
In your repository method, I am not sure what you are doing there but rather than passing in a livedata instance, you should pass in the underlying data of the livedata instance. That way, the observer in the main activity doesn't get triggered everytime you call setIsFavorited(). If you do want to trigger the observer, then you can just call postValue() on the livedata instance. As for the adapter question, I do not know the best practices but I usually create a listener interface so I don't have to pass around my viewmodels everywhere. All of my viewmodels are contained within my fragments and never goes anywhere else. Let me know if this answers your questions.
Also, if you are using viewmodels with recyclerview, consider using list adapters. They are made to work seamlessly with viewmodels. https://developer.android.com/reference/android/support/v7/recyclerview/extensions/ListAdapter
It makes it much simpler to use viewmodels with recyclerview.
Related
I want to use livedata in an recyclerview. But I only want to observe Livedata with a certain ID. The data gets loaded, but it doesn't update.
So here is the function in m Dao:
#Query("SELECT * FROM zutaten_table NATURAL JOIN table_ref WHERE table_ref.rezeptid = :id")
fun getZutatenforRezept(id:Int): LiveData<List<ZutatenData>>
I use a Viewmodel and a repository like this:
class LiveDataZutatenRepository(private val rezeptDao: AllDao, rezeptID: Int){
val Dao = rezeptDao
val allZutaten = Dao.getZutatenforRezept(rezeptID)
}
class SpecialZutatViewmodel(application: Application): AndroidViewModel(application){
private val repository: JustGetSpecialTypesRepository
private lateinit var repositoryLiveData: LiveDataZutatenRepository
lateinit var ZutatenforRezept : LiveData<List<ZutatenData>>
val Dao : AllDao
init {
Dao = EssenRoomDatabase.getDatabase(application, viewModelScope).allDao()
repository = JustGetSpecialTypesRepository(Dao)
}
suspend fun getRezeptWithZutat(id: Int):RezeptWithZutat{
return repository.getRezeptWithZutatFromID(id)
}
suspend fun getMengen(rezid: Int): List<RefZutatRezept>{
return repository.getMengen(rezid)
}
fun setLiveData(rezeptid: Int){
repositoryLiveData = LiveDataZutatenRepository(Dao, rezeptid )
ZutatenforRezept = repositoryLiveData.allZutaten
}
}
an in my view I use an observer to get the livedata:
val zutatViewmodel = ViewModelProvider(this).get(SpecialZutatViewmodel::class.java)
lifecycleScope.launch {
zutatViewmodel.setLiveData(rezeptid)
}
zutatViewmodel.ZutatenforRezept.observe(this, Observer { zutaten ->
zutaten?.let { adapterzut.setZutaten(it) }
})
Viewholder function:
override fun onBindViewHolder(holder: ZutatenViewHolder, position: Int) {
val current = zutaten[position]
holder.rezepteItemView.text = current.zutname
if(current.bild>=0) {
holder.rezeptePicView.setImageResource(current.bild)
holder.rezeptePicView.drawable.isFilterBitmap = false
}
}
unfortenatly the list doesn't update when the database is changed, but is loaded correctly the first time. What am I doing wrong?
it seems you are using room. So, instead of passing the entire list to the adapter, you can pass a list of all the ids in the database. Then, in the onBindViewholder, you can call the rest of the elements by using the id of the element. the code sample below might give you a better idea -
override fun onBindViewHolder(holder: PassViewHolder, position: Int) {
viewModel.getById(getItem(position)).asLiveData().observe(lifecycleOwner) {
try {
holder.bind(it)
}catch (e:Exception){
Log.e(TAG,"PassData passed = null")
e.printStackTrace()
}
}
}
I had the same problem where the views weren't getting updated but the changes where still being recorded. this method fixed it all.
the below piece of code returns the elements linked to the id as a flow.
viewModel.getById(getItem(position))
And then you covert it to live data and add an observer.
if you want, you can have a look at the project where I implemented this
I have a property with late initialization.
Now I want to provide a live data which does not emit anything until the property is initialized completely.
How to do this in proper Kotlin way?
class SomeConnection {
val data: Flow<SomeData>
...
class MyViewModel {
private lateinit var _connection: SomeConnection
// private val _connection: CompletableDeferred<SomeConnection>()
val data = _coonection.ensureInitilized().data.toLiveData()
fun connect(){
viewModelScope.launch {
val conn = establishConnection()
// Here I have to do something for the call ensureInitilized to proceed
}
}
private suspend fun establishConnection(){
...
}
Declare a MutableLiveData emitting values of type SomeConnection and a corresponding LiveData.
private val _connectionLiveData = MutableLiveData<SomeConnection>()
val connectionLiveData: LiveData<SomeConnection> = _connectionLiveData
Then assign value to _connectionLiveData when _connection is initialized:
if (::_connection.isInitialized()) _connectionLiveData.value = _connection
(or _connectionLiveData.postValue(_connection) if your code works concurrently)
Now observe this LiveData in another place in code, I'll use fragment here for the sake of example:
override fun firstOnViewCreated(view: View, savedInstanceState: Bundle?) {
viewModel.connectionLiveData.observe(this, ::sendData)
}
Then send the desired data via the corresponding view model method
I'm working with MVVM, and I have made different implementations of it, but one thing that is still making me doubt is how do I get data from a Repository (Firebase) from my ViewModel without attaching any lifecycle to the ViewModel.
I have implemented observeForever() from the ViewModel, but I don't think that is a good idea because I think I should communicate from my repository to my ViewModel either with a callback or a Transformation.
I leave here an example where I fetch a device from Firebase and update my UI, if we can see here, I'm observing the data coming from the repo from the UI, but from the ViewModel I'm also observing data from the repo, and here is where I really doubt if I'm using the right approach, since I don't know if observeForever() will be cleared on onCleared() if my view is destroyed, so it won't keep the observer alive if the view dies.
UI
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
button.setOnClickListener {
val deviceId = editText.text.toString().trim()
observeData(deviceId)
}
}
fun observeData(deviceId:String){
viewModel.fetchDeviceData(deviceId).observe(this, Observer {
textView.text = "Tipo: ${it.devType}"
})
ViewModel
class MainViewmodel: ViewModel() {
private val repo = Repo()
fun fetchDeviceData(deviceId:String):LiveData<Device>{
val mutableData = MutableLiveData<Device>()
repo.getDeviceData(deviceId).observeForever {
mutableData.value = it
}
return mutableData
}
}
Repository
class Repo {
private val db = FirebaseDatabase.getInstance().reference
fun getDeviceData(deviceId:String):LiveData<Device>{
val mutableData = MutableLiveData<Device>()
db.child(deviceId).child("config/device").addListenerForSingleValueEvent(object: ValueEventListener{
override fun onDataChange(dataSnapshot: DataSnapshot) {
val device = dataSnapshot.getValue(Device::class.java)
mutableData.value = device
}
override fun onCancelled(dataError: DatabaseError) {
Log.e("Error","handle error callback")
}
})
return mutableData
}
}
This example just shows how to fetch the device from Firebase, it works, but from my ViewModel, it keeps making me think that observeForever() is not what I'm looking for to communicate data between the repository to the ViewModel.
I have seen Transformations, but I, in this case, I just need to deliver the entire Device object to my UI, so I don't need to transform the Object I'm retrieving to another Object
What should be here the right approach to communicate the repository and the ViewModel properly?
is observeForever lifecycle aware?
No, that's why it's called observeForever.
I have implemented observeForever() from the ViewModel, but I don't think that is a good idea
No, it's not, you should be using Transformations.switchMap {.
since I don't know if observeForever() will be cleared on onCleared() if my view is destroyed, so it won't keep the observer alive if the view dies.
Well if you're not clearing it in onCleared() using removeObserver(observer), then it won't clear itself, because it observes forever.
here is where I really doubt if I'm using the right approach,
No, you can do much better than this following a reactive approach.
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
button.setOnClickListener {
val deviceId = editText.text.toString().trim()
viewModel.onSelectedDeviceChanged(deviceId)
}
viewModel.selectedDevice.observe(this, Observer { device ->
textView.text = "Tipo: ${device.devType}"
})
}
And
class MainViewModel(
private val savedStateHandle: SavedStateHandle,
): ViewModel() {
private val repo = Repo() // TODO: move to Constructor Argument with ViewModelProvider.Factory
private val selectedDeviceId: MutableLiveData<String> = savedStateHandle.getLiveData<String>("selectedDeviceId")
fun onSelectedDeviceChanged(deviceId: String) {
selectedDeviceId.value = deviceId
}
val selectedDevice = Transformations.switchMap(selectedDeviceId) { deviceId ->
repo.getDeviceData(deviceId)
}
}
And
class Repo {
private val db = FirebaseDatabase.getInstance().reference // TODO: move to constructor arg? Probably
fun getDeviceData(deviceId:String) : LiveData<Device> {
return object: MutableLiveData<Device>() {
private val mutableLiveData = this
private var query: Query? = null
private val listener: ValueEventListener = object: ValueEventListener {
override fun onDataChange(dataSnapshot: DataSnapshot) {
val device = dataSnapshot.getValue(Device::class.java)
mutableLiveData.value = device
}
override fun onCancelled(dataError: DatabaseError) {
Log.e("Error","handle error callback")
}
}
override fun onActive() {
query?.removeEventListener(listener)
val query = db.child(deviceId).child("config/device")
this.query = query
query.addValueEventListener(listener)
}
override fun onInactive() {
query?.removeEventListener(listener)
query = null
}
}
}
}
This way, you can observe for changes made in Firebase (and therefore be notified of future changes made to your values) using LiveData, rather than only execute a single fetch and then not be aware of changes made elsewhere to the same data.
To use ObserveForever, you need to remove the observer inside onClear in the ViewModel.
In this case, I would suggest to use Transformation even though you just need a direct mapping without any processing of the data, which is actually the same as what you are doing with the observer for observerForever.
observeForever() is not Lifecycle aware and will continue to run until removeObserver() is called.
In your ViewModel do this instead,
class MainViewmodel: ViewModel() {
private val repo = Repo()
private var deviceData : LiveData<Device>? = null
fun fetchDeviceData(deviceId:String):LiveData<Device>{
deviceData = repo.getDeviceData(deviceId)
return deviceData!!
}
}
Activity receiving intent
class AddNoteActivity : AppCompatActivity() {
private lateinit var addViewModel: NoteViewModel
private lateinit var titleEditText: TextInputEditText
private lateinit var contentEditText: TextInputEditText
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_add_note_activty)
setSupportActionBar(toolbar)
addViewModel = ViewModelProviders.of(this).get(NoteViewModel::class.java)
titleEditText = findViewById(R.id.itemTitle)
contentEditText = findViewById(R.id.itemNote)
val extra = intent.extras
if (extra != null) {
val uuid = extra.getLong("UUID")
val note: Notes? = addViewModel.getNote(uuid)
titleEditText.setText(note!!.title)
contentEditText.setText(note.note)
}
}
}
NoteViewModel class
class NoteViewModel(application: Application) : AndroidViewModel(application) {
companion object {
private var note: Notes = Notes(0, "", "test title", "test ontent")
}
fun getNote(uuid: Long?): Notes {
val job = async(CommonPool) {
getNoteAsyncTask(notesDatabase).execute(uuid)
}
runBlocking { job.await() }
return note
}
class getNoteAsyncTask(database: NotesDatabase) : AsyncTask<Long, Unit, Unit>() {
private val db: NotesDatabase = database
override fun doInBackground(vararg params: Long?) {
note = db.notesDataDao().getNote(params[0])
}
}
}
If I pass an intent to get a Note object from the database with a uuid and set that received data in titleEditText and contentEditText, the data set in the Note was from previous intent invoked when we clicked on the Note item in RecyclerView. On clicking the Note item for the first time, I get the default value which I have set "test title" and "test content".
Aforementioned is the behavior most of the time. Sometimes the data set in titleEditText and contentEditText is of the correct Note object.
Can someone please tell me what I have done wrong? How can I correct my apps behavior?
Unfortunately, there is a big mistake in how you use a view model to provide a data to your view(AddNoteActivity).
Basically, your view never has a chance to wait for the data to be fetched as it always receives a default value. This happens because the AsyncTask runs on its own thread pool so the coroutine completes immediately and returns a default value.
You should consider using LiveData to post a new object to your view and refactor your view model.
So, you need to make a query to the database synchronous and observe changes to a note rather than have a getter for it. Of course, in a real life scenario it might be a good idea to have different kind of states to be able to show a spinner while a user is waiting. But this is another big question. So to keep things simple consider changing your view model to something like that:
class NoteViewModel(private val database: NotesDatabase) : ViewModel { // you do not need an application class here
private val _notes = MutableLiveData<Notes>()
val notes: LiveData<Notes> = _notes
fun loadNotes(uuid: Long) {
launch(CommonPool) {
val notes = database.notesDataDao().getNote(uuid)
_notes.setValue(notes)
}
}
}
Then, you can observe changes to the note field in your activity.
class AddNoteActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
// ...
val noteViewModel = ViewModelProviders.of(this).get(NoteViewModel::class.java)
noteViewModel.notes.observe(this, Observer {
title.text = it.title
content.text = it.note
})
}
}
Also you need to use a ViewModelProvider.Factory to create your view model and properly inject dependencies into it. Try to avoid having a context there as it makes it much harder to test.
Been using realm and it's awesome.
Came up against something. Wondering if I'm doing something wrong.
I have a RealmRecyclerViewAdapter that I'm using to show the results of a realm query. This works perfectly if I add or update records in the realm. I had to setHasFixedSize(false) on the recycler view to get it to update on the fly. Not sure if this is correct but it worked.
Anyway, that's not my issue.
I'm experimenting with filtering my data. I have the following query:
realm.where(Person::class.java).contains("name", nameFilter, Case.INSENSITIVE).findAllSorted("name")
I'm passing this RealmResults to my recycler view and it works great on add/update.
However, when I attempt a filter, it doesn't update automatically.
Am I right in saying that simply changing my filter (specified by nameFilter) isn't enough for the query to be re-run? This would be fair enough I suppose. Since I guess there's no trigger for realm to know I've changed the value of the string.
However, even if I recalculate my query, it doesn't seem to update in the Recycler View unless I explicitly call updateData on my adapter. I'm not sure if this is the best or most efficient way to do this. Is there a better way?
Complete Code:
Main Activity
class MainActivity : AppCompatActivity(), View.OnClickListener {
private val TAG: String = this::class.java.simpleName
private val realm: Realm = Realm.getInstance(RealmConfiguration.Builder().deleteRealmIfMigrationNeeded().build())
private var nameFilter = ""
private var allPersons: RealmResults<Person> = realm.where(Person::class.java).contains("name", nameFilter, Case.INSENSITIVE).findAllSorted("name")
private val adapter: PersonRecyclerViewAdapter = PersonRecyclerViewAdapter(allPersons)
private lateinit var disposable: Disposable
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
realm.executeTransaction({
// realm.deleteAll()
})
Log.i(TAG, "Deleted all objects from Realm")
buttonAddOrUpdatePerson.setOnClickListener(this)
setUpRecyclerView()
disposable = RxTextView.textChangeEvents(editTextNameFilter)
// .debounce(400, TimeUnit.MILLISECONDS) // default Scheduler is Computation
.observeOn(AndroidSchedulers.mainThread())
.subscribeWith<DisposableObserver<TextViewTextChangeEvent>>(getSearchObserver())
}
private fun getSearchObserver(): DisposableObserver<TextViewTextChangeEvent> {
return object : DisposableObserver<TextViewTextChangeEvent>() {
override fun onComplete() {
Log.i(TAG,"--------- onComplete")
}
override fun onError(e: Throwable) {
Log.i(TAG, "--------- Woops on error!")
}
override fun onNext(onTextChangeEvent: TextViewTextChangeEvent) {
nameFilter = editTextNameFilter.text.toString()
allPersons = realm.where(Person::class.java).contains("name", nameFilter, Case.INSENSITIVE).findAllSorted("name")
// this is necessary or the recycler view doesn't update
adapter.updateData(allPersons)
Log.d(TAG, "Filter: $nameFilter")
}
}
}
override fun onDestroy() {
super.onDestroy()
realm.close()
}
override fun onClick(view: View?) {
if(view == null) return
when(view) {
buttonAddOrUpdatePerson -> handleAddOrUpdatePerson()
}
}
private fun handleAddOrUpdatePerson() {
val personToAdd = Person()
personToAdd.name = editTextName.text.toString()
personToAdd.email = editTextEmail.text.toString()
realm.executeTransactionAsync({
bgRealm -> bgRealm.copyToRealmOrUpdate(personToAdd)
})
}
private fun setUpRecyclerView() {
recyclerViewPersons.layoutManager = LinearLayoutManager(this)
recyclerViewPersons.adapter = adapter
recyclerViewPersons.setHasFixedSize(false)
recyclerViewPersons.addItemDecoration(DividerItemDecoration(this, LinearLayoutManager.VERTICAL))
}
}
PersonRecyclerViewAdapter
internal class PersonRecyclerViewAdapter(data: OrderedRealmCollection<Person>?, autoUpdate: Boolean = true) : RealmRecyclerViewAdapter<Person, PersonRecyclerViewAdapter.PersonViewHolder>(data, autoUpdate) {
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): PersonViewHolder {
val itemView = LayoutInflater.from(parent.context).inflate(R.layout.person_row, parent, false)
return PersonViewHolder(itemView)
}
override fun onBindViewHolder(holder: PersonViewHolder?, position: Int) {
if(holder == null || data == null) return
val personList = data ?: return
val person = personList[position]
holder.bind(person)
}
internal class PersonViewHolder(view: View) : RecyclerView.ViewHolder(view) {
var textViewName: TextView = view.findViewById(R.id.textViewNameDisplay)
var textViewEmail: TextView = view.findViewById(R.id.textViewEmailDisplay)
internal fun bind(person: Person) {
textViewEmail.text = person.email
textViewName.text = person.name
}
}
}
Yeah, updateData() is the way to do it. Since you updated the query, the Results you want to show becomes a different object. updateData() has to be called to notify the adapter that the data source is changed.
However, you may lose the nice animation for the RecyclerView in this way since the whole view will be refreshed because of the data source is changed. There are some ways to work around this.
eg.: You can add one field isSelected to Person. Query the results by isSelected field and pass it to the adaptor:
allPersons = realm.where(Person::class.java).equalTo("isSelected", true).findAllSorted("name")
adapter = PersonRecyclerViewAdapter(allPersons)
When changing the query:
realm.executeTransactionAsync({
var allPersons = realm.where(Person::class.java).equalTo("isSelected", true).findAllSorted("name")
for (person in allPersons) person.isSelected = false; // Clear the list first
allPersons = realm.where(Person::class.java).contains("name", nameFilter, Case.INSENSITIVE).findAllSorted("name") // new query
for (person in allPersons) person.isSelected = true;
})
It depends on your use case, if the list to show is long, this approach might be slow, you could try to add all the filtered person to a RealmList and set the RealmList as the data source of the adapter. RealmList.clear() is a fast opration than iterating the whole results set to set the isSelected field.
If the filter will mostly cause the whole view gets refreshed, updateData() is simply good enough, just use it then.