Develop Reference

Room livedata , databinding issue : UI doesn't update when data changes

I am now developing an application where I use MVVM pattern for UI and repository interaction. In other words, I receive live data object with a list of models from my ROOM data base query via repository, then assign it to my live data variable in viewmodel. After that, this data should be populated to my xml layout recycler view via data binding, but It happens only once fragment is initialised. In other cases recycler view is void
DAO code :
#Query("SELECT * FROM note WHERE content LIKE :query ORDER BY isStarred")
fun searchAllNotes(query : String?) : Flow<List<Note>>
ViewModel code:
#HiltViewModel
class HomeViewModel #Inject constructor (
private val noteRepository : NoteRepository
) : ViewModel() {
private var _notesLiveData : LiveData<List<Note>> = noteRepository.getAllNotes().asLiveData()
val notesLiveData get()= _notesLiveData
fun searchNotes(query : String){
viewModelScope.launch(Dispatchers.IO){
_notesLiveData = noteRepository.searchAllNotes(query).asLiveData()
}
}
fun deleteNote(note : Note){
viewModelScope.launch(Dispatchers.IO){
noteRepository.deleteNote(note)
}
}
fun updateNoteChecked(note : Note){
viewModelScope.launch(Dispatchers.IO){
noteRepository.updateNoteChecked(note.id, note.isStarred)
}
}
Fragment code
#AndroidEntryPoint
class HomeFragment : Fragment(),
NoteCardAdapter.NoteTouchListener,
SearchView.OnQueryTextListener{
private var _binding : FragmentHomeBinding? = null
val binding get() = _binding!!
private val adapter by lazy {
NoteCardAdapter(this as NoteCardAdapter.NoteTouchListener)
}
private val vm : HomeViewModel by viewModels()
private val noteSharedViewModel : NoteSharedViewModel by activityViewModels()
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View {
_binding = FragmentHomeBinding.inflate(inflater)
return binding.root
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
binding.adapter = adapter
binding.vm = vm
binding.apply {
lifecycleOwner = viewLifecycleOwner
homeRecyclerView.isNestedScrollingEnabled = false
homeRecyclerView.layoutManager = LinearLayoutManager(view.context)
homeRecyclerView.itemAnimator= NotesItemAnimator()
}
binding.homeSearchView.isSubmitButtonEnabled = true
binding.homeSearchView.setOnQueryTextListener(this as SearchView.OnQueryTextListener)
binding.addNoteButton.setOnClickListener{
val note = Note(
"","","",false, activity?.getDate(), folderId = -1
)
noteSharedViewModel.selectNote(note)
val action = HomeFragmentDirections.actionHomeFragmentToSingleNoteFragment(
isNew = true
)
findNavController().navigate(action)
}
binding.foldersButton.setOnClickListener{
findNavController().navigate(HomeFragmentDirections.actionHomeFragmentToFoldersFragment())
}
}
xml layout code :
<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
>
<data>
<variable
name="vm"
type="com.example.leonidsnotesapplication.presentation.notes_feature.viewmodels.HomeViewModel" />
<variable
name="adapter"
type="com.example.leonidsnotesapplication.presentation.notes_feature.adapters.NoteCardAdapter" />
</data>
<androidx.constraintlayout.widget.ConstraintLayout
android:background="#color/note_background_color_3"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".presentation.notes_feature.fragments.HomeFragment">
<androidx.appcompat.widget.SearchView
android:id="#+id/homeSearchView"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_margin="10dp"
android:theme="#style/AppSearchView"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintStart_toStartOf="parent"/>
<TextView
android:id="#+id/tvRecentTitle"
android:textStyle="bold"
android:textSize="25sp"
android:textColor="#color/button_color_2"
android:text="#string/recent"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="20dp"
android:layout_marginStart="20dp"
app:layout_constraintTop_toBottomOf="#id/homeSearchView"
app:layout_constraintStart_toStartOf="parent"/>
<ImageView
android:layout_width="24dp"
android:layout_height="24dp"
android:layout_marginStart="16dp"
android:layout_marginTop="28dp"
android:background="#drawable/ic_circle_arrow"
app:layout_constraintStart_toEndOf="#id/tvRecentTitle"
app:layout_constraintTop_toBottomOf="#id/homeSearchView" />
<androidx.recyclerview.widget.RecyclerView
tools:listitem="#layout/note_card_view"
android:scrollbars="vertical"
android:scrollbarStyle="outsideInset"
android:id="#+id/homeRecyclerView"
android:layout_width="match_parent"
android:requiresFadingEdge="vertical"
android:fadingEdge="vertical"
android:fadingEdgeLength="15dp"
android:layout_height="500dp"
android:layout_marginTop="30dp"
app:setNoteAdapter="#{adapter}"
app:submitNoteList="#{vm.notesLiveData}"
app:layout_constraintTop_toBottomOf="#id/tvRecentTitle"
app:layout_constraintStart_toStartOf="parent"
/>
<com.google.android.material.floatingactionbutton.FloatingActionButton
android:backgroundTint="#color/button_color_1"
android:id="#+id/add_note_button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_margin="16dp"
android:src="#drawable/ic_create"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent" />
<com.google.android.material.floatingactionbutton.FloatingActionButton
android:backgroundTint="#color/button_color_1"
android:id="#+id/folders_button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_margin="16dp"
android:src="#drawable/ic_folders_stack"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintStart_toStartOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
</layout>
Data binding adapter :
#BindingAdapter("submitNoteList")
fun submitNoteList(recyclerView: RecyclerView, data : List<Note>?){
val adapter = recyclerView.adapter as NoteCardAdapter
adapter.setData((data as ArrayList<Note>? ?: arrayListOf()))
}
#BindingAdapter("setNoteAdapter")
fun setNoteAdapter(recyclerView: RecyclerView, adapter: NoteCardAdapter){
adapter.let {
recyclerView.adapter = it
}
}

You should observe your live data. Example code is:
vm.notesLiveData.observe(viewLifecycleOwner) { adapter.submitList(it) }

Using data bindings in Fragments

I have a problem using viewmodel in fragment with data binding.
In my programm i'm using only one activity and fragments. I organized transitions between fragments using navigation. And i want to use data binding in my fragment, but when running the application only with binding, everything works well when I pass to the binding viewmodel when switching to this fragment of the application, it crashes.
I would be very grateful for your help!
My fragment
class TimeSettings : Fragment() {
private lateinit var viewModel: TimeSettingsViewModel
private lateinit var binding: FragmentTimeSettingsBinding
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
binding = FragmentTimeSettingsBinding.inflate(inflater, container, false)
binding.lifecycleOwner = this
binding.viewmodel = viewModel;
return binding.root
}
}
Object for viewmodel
object TimeData {
var inhale: Int = 4
private val _currentTimeInhale = MutableLiveData<Int>()
val currentTimeInhale: LiveData<Int>
get() = _currentTimeInhale
init{
_currentTimeInhale.value = inhale
}
fun changeCurrentTimeInhale(){
_currentTimeInhale.value = 5
}
}
Viewmodel
class TimeSettingsViewModel : ViewModel() {
val currentInhale: LiveData<Int>
get() = TimeData.currentTimeInhale
fun onChange() = TimeData.changeCurrentTimeInhale()
}
xml file for fragment
<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools">
<data>
<variable
name="viewmodel"
type="ivakin.first.my_first_app.viewmodels.TimeSettingsViewModel" />
</data>
<androidx.constraintlayout.widget.ConstraintLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<TextView
android:id="#+id/textView"
android:layout_width="95dp"
android:layout_height="59dp"
android:text="#{viewmodel.currentInhale}"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_bias="0.452" />
<Button
android:id="#+id/button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Set"
android:onClick="#{()->viewmodel.onChange()"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="#+id/textView" />
</androidx.constraintlayout.widget.ConstraintLayout>
</layout>

U Forgot Initialize ViewModel :
viewmodel = TimeSettingsViewModel()
Also dont use return binding.root

DataBinding doesn't update value when changing LiveData

I want the value to increase when I press the button and write it in the textview.
However, the code below shows the increasing value as Log
But, on screen, the value in textview does not change.
I'm not sure what's wrong. Please let me know if you know.
Fragment.kt
class SettingFragment : Fragment(), View.OnClickListener {
companion object {
fun newInstance() = SettingFragment()
private val TAG = "SettingFragment"
}
private lateinit var viewModel: SettingViewModel
private lateinit var binding: FragmentSettingBinding
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
binding = DataBindingUtil.inflate(inflater, R.layout.fragment_setting, container, false)
return binding.root
}
override fun onActivityCreated(savedInstanceState: Bundle?) {
super.onActivityCreated(savedInstanceState)
viewModel = ViewModelProvider(this).get(SettingViewModel::class.java)
binding.lifecycleOwner = this
binding.button.setOnClickListener(this)
}
override fun onClick(v: View?) {
viewModel.increase()
Log.d(TAG, "Log Data" + viewModel.testInt.value)
}
}
FragmentViewModel
class SettingViewModel : ViewModel() {
val testInt: MutableLiveData<Int> = MutableLiveData()
init {
testInt.value = 0
}
fun increase() {
testInt.value = testInt.value?.plus(1)
}
}
fragment.xml
<?xml version="1.0" encoding="utf-8"?>
<layout>
<data>
<variable
name="viewModel"
type="com.example.ui.setting.SettingViewModel" />
</data>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context=".ui.setting.SettingFragment">
<TextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="#{String.valueOf(viewModel.testInt)}" />
<Button
android:id="#+id/button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
/>
</LinearLayout>
</layout>

<variable
name="viewModel"
type="com.example.ui.setting.SettingViewModel" />
This viewModel variable doesn't bind to a certain variable programmatically. So, when the value incremented, it won't reflect to the layout.
To fix this set the fragment's viewModel to this value:
viewModel = ViewModelProvider(this).get(SettingViewModel::class.java)
binding.viewModel = viewModel // <<<<< Here is the change
binding.lifecycleOwner = this
binding.button.setOnClickListener(this)
Side note:
You shouldn't use onActivityCreated() as it's is deprecated as of API level 28; you can normally its part of code to onCreateView(). And you can check here for other alternatives.

How can a ViewModel function access the Place instance returned by PlaceSelectionListener of AutocompleteSupportFragment?

I am building an Android app using Kotlin.
I have a layout that contains a create_button. When the user clicks the button, the onClick should call onCreateJourney() in my ViewModel. This function requires the selectedPlaceId parameter to update a Journey entity with its value.
In my Fragment, I use the AutocompleteSupportFragment for the user to search and choose the desired place. This works well, as onPlaceSelected() returns the correct place in response to the user's selection. But I can't figure out how to use the returned place id value (p0.id) in my ViewModel onCreateJourney().
At this stage, the compiler throws this error:
cannot find method onCreateJourney() in class com.example.traveljournal.journey.NewJourneyViewModel
Please, can you shed some light on this issue for me?
My UI (.xml fragment layout):
<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
tools:context=".journey.NewJourneyFragment">
<data>
<variable
name="newJourneyViewModel"
type="com.example.traveljournal.journey.NewJourneyViewModel" />
</data>
<androidx.constraintlayout.widget.ConstraintLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<TextView
android:id="#+id/whereQuestion"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="10dp"
android:layout_marginTop="20dp"
android:layout_marginEnd="10dp"
android:text="#string/whereQuestion"
android:textSize="18sp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.027"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="#+id/journeyBckgImageView" />
<androidx.cardview.widget.CardView
android:id="#+id/cardView"
android:layout_width="match_parent"
android:layout_height="wrap_content"
app:layout_constraintBottom_toBottomOf="parent">
</androidx.cardview.widget.CardView>
<fragment
android:id="#+id/autocomplete_fragment"
android:name="com.google.android.libraries.places.widget.AutocompleteSupportFragment"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginStart="10dp"
android:layout_marginTop="10dp"
android:layout_marginEnd="10dp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="#+id/whereQuestion" />
<Button
android:id="#+id/create_button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginBottom="16dp"
android:onClick="#{() -> newJourneyViewModel.onCreateJourney()}"
android:text="#string/createJourneyButton"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
</layout>
My ViewModel
class NewJourneyViewModel (
private val journeyKey: Long = 0L,
val database: TravelDatabaseDao) : ViewModel() {
private var viewModelJob = Job()
private val uiScope = CoroutineScope(Dispatchers.Main + viewModelJob)
private val _navigateToJourneys = MutableLiveData<Boolean?>()
val navigateToJourneys: LiveData<Boolean?>
get() = _navigateToJourneys
fun doneNavigating() {
_navigateToJourneys.value = null
}
fun onCreateJourney(selectedPlaceId: String) {
uiScope.launch {
withContext(Dispatchers.IO) {
val journey = database.getJourney(journeyKey) ?: return#withContext
journey.placeId = selectedPlaceId
database.updateJourney(journey)
}
_navigateToJourneys.value = true
}
}
override fun onCleared() {
super.onCleared()
viewModelJob.cancel()
}
}
My Fragment
class NewJourneyFragment : Fragment(), PlaceSelectionListener {
override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
(activity as AppCompatActivity).supportActionBar?.title = getString(R.string.createJourney)
val binding: FragmentNewJourneyBinding = DataBindingUtil.inflate(
inflater,
R.layout.fragment_new_journey, container, false
)
val application = requireNotNull(this.activity).application
val arguments = NewJourneyFragmentArgs.fromBundle(arguments!!)
val dataSource = TravelDatabase.getInstance(application).travelDatabaseDao
val viewModelFactory = NewJourneyViewModelFactory(arguments.journeyKey, dataSource)
val newJourneyViewModel =
ViewModelProviders.of(
this, viewModelFactory).get(NewJourneyViewModel::class.java)
binding.newJourneyViewModel = newJourneyViewModel
newJourneyViewModel.navigateToJourneys.observe(this, Observer {
if(it == true) {
this.findNavController().navigate(
NewJourneyFragmentDirections.actionNewJourneyDestinationToJourneysDestination())
newJourneyViewModel.doneNavigating()
}
})
if (!Places.isInitialized()) {
this.context?.let { Places.initialize(it, getString(R.string.apiKey), Locale.US) }
}
val autocompleteFragment = childFragmentManager.findFragmentById(R.id.autocomplete_fragment)
as? AutocompleteSupportFragment
autocompleteFragment?.setOnPlaceSelectedListener(this)
autocompleteFragment!!.setHint(getString(R.string.destinationExample))
autocompleteFragment!!.setPlaceFields(Arrays.asList(Place.Field.ID, Place.Field.NAME))
return binding.root
}
#ExperimentalStdlibApi
override fun onPlaceSelected(p0: Place) {
Log.i("PLACE", "Place: " + p0.name + ", " + p0.id)
}
override fun onError(status: Status) {
Toast.makeText(this.context,""+status.toString(),Toast.LENGTH_LONG).show()
Log.i("ERROR", "An error occurred: " + status)
}
}

You have to pass the field selectedPlaceId as an argument in the xml :
android:onClick="#{() -> newJourneyViewModel.onCreateJourney(newJourneyViewModel.selectedPlaceId)}"
How will you get the selectedPlaceId in view model depends on your programming logic.
For testing purposes, you can hardcode the value.

In NewJourneyViewModel, I set up selectedPlaceId as MutableLiveData.
val selectedPlaceId = MutableLiveData<String>()
In NewJourneyFragment, I used lateinit to create a field for NewJourneyViewModel called newJourneyViewModel and initialized it in onCreateView().
private lateinit var newJourneyViewModel : NewJourneyViewModel
Now having access to my ViewModel outside of onCreateView(), in my Fragment onPlaceSelected() method I can set the value of selectedPlaceId to p0.id.
newJourneyViewModel.selectedPlaceId.value = p0.id
If anybody can come up with a better and safer approach on this, it will be highly appreciated.

How to use a MutableLiveData Object in my xml?

I have an object that will fill some fields in my xml, but a mutablelivedata return a T value and I can't use the T properties. What I need to do to use the T object in my xml?
I don't want to create a mutablelivedata for each object member.
Sorry for my bad english..
class ExampleFragment: Fragment() {
override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
val viewModel = ViewModelProviders.of(this).get(MyVm::class.java)
val binding = DataBindingUtil.inflate<FragmentExampleBinding>(
inflater,
R.layout.fragment_house,
container,
false
)
binding.myVm = viewModel
binding.lifecycleOwner = this
return binding.root
}
}
class MyVm: ViewModel(){
val house: MutableLiveData<House> by lazy { MutableLiveData<House>().apply{ value =
House().apply{
door = "First door"
window = "My window"
}
} }
val thing: MutableLiveData<String> by lazy { MutableLiveData<String>().apply{ value = "something" } }
}
class House(){
var door: String = ""
var window: String = ""
}
<layout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto">
<data>
<variable name="my_vm" type="br.com.MyVm"/>
</data>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
orientation="vertical"
>
<!--I need this work-->
<TextView
android:layout_width="wrap_parent"
android:layout_height="wrap_parent"
android:text="my_vm.house.door"
/>
<!--I need this work-->
<TextView
android:layout_width="wrap_parent"
android:layout_height="wrap_parent"
android:text="my_vm.house.window"
/>
<TextView
android:layout_width="wrap_parent"
android:layout_height="wrap_parent"
android:text="my_vm.thing"
/>
</LinearLayout>
<layout>

This code is correcty! A tried run and worked, I thounght it didn't work because the android studio didn't show the attributes when press ctrl + space.