I'm learning Room with the sample project RoomWordsSample at https://github.com/googlecodelabs/android-room-with-a-view/tree/kotlin.
The following code are from the project.
In my mind, the LiveDate will update UI automatically when the data changed if it was observed.
But in the file WordListAdapter.kt, I find notifyDataSetChanged() is added to the function setWords(words: List<Word>)， it's seems that it must notify UI manually when data changed.
Why do it still need launch notifyDataSetChanged() when I have used LiveData ?
MainActivity.kt
class MainActivity : AppCompatActivity() {
private val newWordActivityRequestCode = 1
private lateinit var wordViewModel: WordViewModel
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
val recyclerView = findViewById<RecyclerView>(R.id.recyclerview)
val adapter = WordListAdapter(this)
recyclerView.adapter = adapter
recyclerView.layoutManager = LinearLayoutManager(this)
wordViewModel = ViewModelProvider(this).get(WordViewModel::class.java)
wordViewModel.allWords.observe(this, Observer { words ->
words?.let { adapter.setWords(it) }
})
}
}
WordViewModel.kt
class WordViewModel(application: Application) : AndroidViewModel(application) {
private val repository: WordRepository
val allWords: LiveData<List<Word>>
init {
val wordsDao = WordRoomDatabase.getDatabase(application, viewModelScope).wordDao()
repository = WordRepository(wordsDao)
allWords = repository.allWords
}
fun insert(word: Word) = viewModelScope.launch {
repository.insert(word)
}
}
WordListAdapter.kt
class WordListAdapter internal constructor(
context: Context
) : RecyclerView.Adapter<WordListAdapter.WordViewHolder>() {
private val inflater: LayoutInflater = LayoutInflater.from(context)
private var words = emptyList<Word>() // Cached copy of words
inner class WordViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
val wordItemView: TextView = itemView.findViewById(R.id.textView)
}
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): WordViewHolder {
val itemView = inflater.inflate(R.layout.recyclerview_item, parent, false)
return WordViewHolder(itemView)
}
override fun onBindViewHolder(holder: WordViewHolder, position: Int) {
val current = words[position]
holder.wordItemView.text = current.word
}
internal fun setWords(words: List<Word>) {
this.words = words
notifyDataSetChanged()
}
override fun getItemCount() = words.size
}
Actually, livedata will give you updated data in your activity. But now, it is your activity's job to update the ui. So, whenever live data gives you updated data, you will have to tell the ui to update the data. Hence, notifyDataSetChanged().
notifyDataSetChanged has nothing to do with LiveData, it's part of RecyclerView api.
LiveData - is way of receiving data in lifecycle-aware way, RecyclerView simply displays views.
Related
In my application I want use Koin , Room and LiveData.
I write below codes, but after add new item into room not auto update recyclerview list!
Should close app and open again for show updated list !
Dao codes :
#Query("SELECT * FROM $NOTE_TABLE")
fun getAllNote(): MutableList<NoteModel>
Repository codes :
class RoomRepository(private val dao: NoteDao) {
suspend fun saveNote(note: NoteModel) = dao.saveNote(note)
fun getAllNotes() = dao.getAllNote()
}
ViewModel codes:
class RoomViewModel(private val repository: RoomRepository) : ViewModel() {
val notesList = MutableLiveData<MutableList<NoteModel>>()
fun saveNote(note:NoteModel) = viewModelScope.launch {
repository.saveNote(note)
}
fun loadAllNotes() = viewModelScope.launch {
val list = repository.getAllNotes()
if (list.isNotEmpty()) {
notesList.postValue(list)
}
}
}
Activity codes :
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
binding = ActivityKoinRoomBinding.inflate(layoutInflater)
setContentView(binding.root)
//InitViews
binding.apply {
//Save
btnSave.setOnClickListener {
val title = titleEdt.text.toString()
note.id = 0
note.title = title
viewModel.saveNote(note)
}
//Load notes
viewModel.loadAllNotes()
viewModel.notesList.observe(this#KoinRoomActivity) {
noteAdapter.differ.submitList(it)
notesList.apply {
layoutManager = LinearLayoutManager(this#KoinRoomActivity)
adapter = noteAdapter
}
}
}
How can I fix this issue?
In order to update data immediately, you need to return LiveData<T> from the database itself. In your case, do something like that:
#Query("SELECT * FROM $NOTE_TABLE")
fun getAllNote(): LiveData<List<NoteModel>>
I also changed MutableList to List, because there is no need for mutability here.
You ViewModel can then be like this:
class RoomViewModel(private val repository: RoomRepository) : ViewModel() {
val notesList = repository.getAllNotes()
...
}
and you can also remove function loadAllNotes() from it.
It's first time using Room Data while also using MVVM pattern. The aim is that I want my data to appeard on the RecyclerList but it's doesn't shut down nor shows me any error it's just appears empty.
Here is my Database class:
#Database(entities = [Plant::class, Plant_Category::class], version = 1)
abstract class PlantDatabase:RoomDatabase() {
abstract fun plantDao(): PlantOperations
abstract fun plantCategoryDao(): PlantCategoryOperations
companion object {
private var INSTANCE: PlantDatabase? = null
fun getDatabase(context: Context): PlantDatabase {
if (INSTANCE == null) {
INSTANCE = Room.databaseBuilder(
context.applicationContext,
PlantDatabase::class.java, DB_NAME // contains directory of sqlite database
)
.fallbackToDestructiveMigration()
.build()
}
return INSTANCE!!
}
}
}
My dao class:
#Dao
interface PlantOperations {
#Query("SELECT * FROM Plant")
fun getAll(): Flow<List<Plant>>
#Insert
fun insertPlant( plant: Plant)
#Delete
fun delete(plant:Plant)
#Update
fun updatePlant(plant:Plant)}
This is my repository class:
class PlantRepository(application:Application){
private var allPlants = MutableLiveData<List<Plant>>()
private val plantDAO = PlantDatabase.getDatabase(application).plantDao()
init {
CoroutineScope(Dispatchers.IO).launch {
val plantData = plantDAO.getAll()
plantData.collect{
allPlants.postValue(it)
}
}
}
fun getAllPlants(): MutableLiveData<List<Plant>> {
return allPlants
}
}
My Viewmodel class:
class PlantViewModel(
application: Application
): AndroidViewModel(application) {
private var repository = PlantRepository(application)
private var _allPlants = repository.getAllPlants()
val allPlants: MutableLiveData<List<Plant>>
get() = _allPlants
}
My Recycler in Fragment:
override fun onCreateView(inflater: LayoutInflater,
container: ViewGroup?, savedInstanceState: Bundle?): View? {
lateinit var photoAdapter: Photo_Adapter
lateinit var plantViewModel: PlantViewModel
val view: View = inflater.inflate(R.layout.fragment_edit__form, container, false)
val fab = view.findViewById(R.id.floatingActionButton) as FloatingActionButton
val recyclerView = view.findViewById(R.id.recyclerView) as RecyclerView
recyclerView.layoutManager = GridLayoutManager(context, 2)
photoAdapter = Photo_Adapter(context)
recyclerView.adapter = photoAdapter
plantViewModel = ViewModelProvider(this).get(PlantViewModel::class.java)
plantViewModel.allPlants.observe(viewLifecycleOwner, androidx.lifecycle.Observer {
photoAdapter.setDataList(it)
})
// photoAdapter.setDataList(dataList)
//Floating button that opens the Form in order to add plant
fab?.setOnClickListener {
val intent = Intent(view.context, Edit_Form::class.java)
startActivity(intent);
}
return view
}
This is my adapter class:
class Photo_Adapter(var context: Context?) : RecyclerView.Adapter<Photo_Adapter.ViewHolder>() {
var dataList = emptyList<Plant>()
internal fun setDataList(dataList: List<Plant>) {
this.dataList = dataList
notifyDataSetChanged()
}
override fun onBindViewHolder(holder: ViewHolder, position: Int) {
// Get the data model based on position
var data = dataList[position]
holder.title.text = data.name
holder.desc.text = data.type.toString()
holder.image.setImageResource(data.image)
holder.relativeLayout.setOnClickListener { view -> //Toast.makeText(view.getContext(),"click on item: "+model.getTitle(),Toast.LENGTH_LONG).show();
val intent = Intent(view.context, PlantDetails::class.java)
intent.putExtra("plant_name", data.name)
intent.putExtra("plant_image",data.image)
intent.putExtra("plant_type", data.type.type)
intent.putExtra("plant_water", data.type.water_time)
intent.putExtra("plant_details", data.type.details)
view.context.startActivity(intent)
}
}
// Provide a direct reference to each of the views with data items
class ViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
var image: ImageView
var title: TextView
var desc: TextView
var relativeLayout: CardView
init {
image = itemView.findViewById(R.id.image)
title = itemView.findViewById(R.id.title)
desc = itemView.findViewById(R.id.desc)
relativeLayout = itemView.findViewById<View>(R.id.relativeLayout) as CardView
}
}
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): Photo_Adapter.ViewHolder {
// Inflate the custom layout
var view = LayoutInflater.from(parent.context).inflate(R.layout.photo_layout, parent, false)
return ViewHolder(view)
}
// total count of items in the list
override fun getItemCount() = dataList.size
}
Perhaps I forgot to add something? In Anyway I will be grateful for your help.
You should not observe data on your repository, your activity/view should observe this data. Take a look at this:
First, add this dependency to your gradle:
implementation "androidx.lifecycle:lifecycle-livedata-ktx:2.3.1"
Then in your repository
class PlantRepository(application:Application){
private val plantDAO = PlantDatabase.getDatabase(application).plantDao()
fun getAllPlants(): Flow<List<Plant>> = plantDAO.getAll()
}
In your view model:
class PlantViewModel(
application: Application
): AndroidViewModel(application) {
private var repository = PlantRepository(application)
val allPlants = repository.getAllPlants()
.flowOn(Dispatchers.IO)
.asLiveData()
}
And your activity is fine, but check your adapter, make sure that you're notifing your adapter that your list has changed.
You can also work (collect) flows on your view, but this depends on you
The problem I am facing with the RecyclerView is the data is coming from Server and the API response is getting printed correctly in the console.
but when I am trying to set data in the adapter what is wrong or something is not going correctly with the flow that the data is not being updated on UI.
//This is my adapter class
class DashboardAdapter(val context: Context) : RecyclerView.Adapter<DashBoardHolder>() {
private var transactionList = ArrayList<DashboardData>()
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): DashBoardHolder {
val inflator = LayoutInflater.from(parent.context)
val view = ActivityDashboardDataBinding.inflate(inflator, parent, false)
val viewHolder = DashBoardHolder(view)
return viewHolder
}
override fun onBindViewHolder(holder: DashBoardHolder, position: Int) {
val quickModel = transactionList[position]
holder.tvName.text = quickModel.bookingTitle
}
fun showListItems(dashboardlist: List<DashboardData>?, aboolean: Boolean) {
when {
aboolean -> transactionList.clear()
}
if (dashboardlist != null && !dashboardlist.isEmpty())
this.transactionList.addAll(dashboardlist)
notifyDataSetChanged()
}
override fun getItemCount(): Int {
return transactionList.size
}
}
MyHolderClass
class DashBoardHolder(val binding: ActivityDashboardDataBinding) :
RecyclerView.ViewHolder(binding.root) {
var tvName: TextView = binding.textViewGrandrukName
var tvTime: TextView = binding.tvGrandrukTripDetails
var tvPlace: ImageView = binding.btnGhandruk
var ivRectangle: ImageView = binding.imageView5
}
Similarly,I set the adapter in view section like this way:
//setting adapter in Presenter class
fun setAdapter() {
var layoutmanager: LinearLayoutManager? = LinearLayoutManager(appCompatActivity)
val firstVisiblePosition = layoutmanager!!.findFirstVisibleItemPosition()
binding!!.includesDashboardRecyclerview.rvBookingList.setHasFixedSize(true)
binding!!.includesDashboardRecyclerview.rvBookingList.layoutManager = layoutmanager
binding!!.includesDashboardRecyclerview.rvBookingList.adapter = dashboardAdapter
layoutmanager!!.scrollToPositionWithOffset(firstVisiblePosition, 0)
}
In Presenter Class, calling setAdapter class from presenter like this way
class DashboardPresenter(
private val dashboardView: DashboardView,
private val dashboardModel: DashboardModel
) {
fun onCreateView() {
onClick()
dashboardView.setAdapter()
getDashboardRequest()
}
//calling adpter function here
fun showList(termlist: List<DashboardData>?, aboolean: Boolean) {
(null as DashboardAdapter?)?.showListItems(termlist!!, aboolean)
}
}
I'm not able to understand what is getting wrong here.
(null as DashboardAdapter?)?.showListItems(termlist!!, aboolean)
You are calling showListItems() on the DashboardAdapter as a type not the instance dashboardAdapter. Assuming that dashboardAdapter is a local class field.
Also I guess this type casting is not necessary as you already using the optional ?
So, it can be simplified to:
dashboardAdapter?.showListItems(termlist!!, aboolean)
Assuming that this should be called whenever you retrieve the API response. So, showList() must be called when there's new API data.
I have implemented RecyclerView in my app with Kotlin using Refrofit, MVVM, DataBinding, Coroutines. The same code works fine in another fragment but not here.
*Note: The retrofit functions returns the commentsList successfully but only problem in displaying the list in a recyclerView.
override fun onActivityCreated(savedInstanceState: Bundle?) {
super.onActivityCreated(savedInstanceState)
val api = ApiRepository()
factory = CommentsViewModelFactory(api)
viewModel = ViewModelProvider(this, factory).get(CommentsViewModel::class.java)
viewModel.getComments(requireActivity())
viewModel.commentsList.observe(viewLifecycleOwner, Observer { comments ->
rvComment.also {
it.layoutManager = LinearLayoutManager(requireContext())
it.setHasFixedSize(true)
if (comments != null) {
it.adapter = HomeServicesCommentsAdapter(comments, this)
}
}
})
}
The ViewModel looks like this, i declared the comments as MutableLiveData, which returns the data successfully but the only issue is with the adapter attachment.
class CommentsViewModel(private val repository: ApiRepository) : ViewModel() {
var userComment: String? = null
private val comments = MutableLiveData<List<Comment>>()
private lateinit var job: Job
val commentsList: MutableLiveData<List<Comment>>
get() = comments
fun getComments(context: Context) {
job = CoroutinesIO.ioThenMain(
{
repository.getServices(context)
}, {
for (i in it!!.data.data)
comments.value = i.comments
}
)
}
Here is the adapter implementation
class HomeServicesCommentsAdapter(
private val comments: List<Comment>,
private val listenerService: RvListenerServiceComments
) : RecyclerView.Adapter<HomeServicesCommentsAdapter.ServicesViewHolder>() {
override fun getItemCount() = comments.size
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int) =
ServicesViewHolder(
DataBindingUtil.inflate(
LayoutInflater.from(parent.context),
R.layout.custom_comment_layout,
parent,
false
)
)
override fun onBindViewHolder(holder: ServicesViewHolder, position: Int) {
holder.recyclerViewServicesBinding.comments = comments[position]
notifyDataSetChanged()
}
class ServicesViewHolder(
val recyclerViewServicesBinding: CustomCommentLayoutBinding
) : RecyclerView.ViewHolder(recyclerViewServicesBinding.root)
}
Let me know if you need the xml layout files.
Instead of giving layout manager at runtime while observing data ,
Define layoutmanager inside xml
eg:
<androidx.recyclerview.widget.RecyclerView
android:id="#+id/rvNews"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:nestedScrollingEnabled="false"
tools:listitem="#layout/item_your_layout"
app:layoutManager="androidx.recyclerview.widget.LinearLayoutManager" />
Remove below lines from observer
it.layoutManager = LinearLayoutManager(requireContext())
EDIT:
Do not create instance of adapter while observing data because observing data is not on MainThread So make sure you set data on MainThread
val adapter = HomeServicesCommentsAdapter(arrayListOf(), this)
rvComment?.adapter = adapter
viewModel.getComments(requireActivity())
viewModel.commentsList.observe(viewLifecycleOwner, Observer { comments ->
comments?.let{adapter.setData(comments)}//define setData(list:ArrayList<Comments>) method in your adapter
})
HomeServicesCommentsAdapter.kt:
........
private var mObjects: MutableList<Comment>? = ArrayList()// top level declaration
fun setData(objects: List<Comment>?) {
this.mObjects = objects as MutableList<Comment>
this.notifyDataSetChanged()
}
......
I have a Fragment with a RecyclerView in it. I use a ViewModel to hold the LiveData to show from a Room database and try to update the RecyclerView by observing the data in the ViewModel. But the Observer only ever gets called once when I open the fragment. I update the Room databse from a different Fragment than the Observer is on.
Wheter I add a new Event or delete or update one, the Observer never gets called! How can I get the Observer to be called properly? Where is my mistake?
Fragment
The code in onViewCreated does not work in onCreate, it return null on the line val recyclerview = upcoming_recycler.
You also see at the end of onViewCreated where I open a new fragment, from which the database gets updated. Note that the UpcomingFragment is in a different FragmentLayout than the EventEditFragment!
class UpcomingFragment : Fragment(R.layout.fragment_upcoming) {
private val clubDb by lazy {
ClubDatabase.getClubDatabase(requireContext().applicationContext)
}
private val eventAdapter = EventAdapter(null, this)
private val upcomingViewModel: UpcomingViewModel by viewModels()
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
val recyclerView = upcoming_recycler
recyclerView.layoutManager = LinearLayoutManager(context)
recyclerView.setHasFixedSize(true)
upcomingViewModel.eventsToShow.observe(viewLifecycleOwner, Observer { events ->
Log.d(TAG, "Live data changed in upcomingfragment!!!")
eventAdapter.setData(events.toTypedArray())
})
recyclerView.adapter = eventAdapter
// add a new Event
upcoming_fab.setOnClickListener {
parentFragmentManager.beginTransaction()
.replace(R.id.main_fragment_layout_overlay, EventEditFragment())
.addToBackStack(EVENT_EDIT_FRAGMENT)
.commit()
}
// and more stuff...
}
//the rest of the class
}
ViewModel
class UpcomingViewModel(application: Application) : ViewModel() {
val eventsToShow: LiveData<List<Event>>
init {
val roundToDay = SimpleDateFormat("dd.MM.yyy", Locale.GERMAN)
var today = Date()
today = roundToDay.parse(roundToDay.format(today))!!
val tomorrow = Date(today.time + 86400000L)
eventsToShow = ClubDatabase.getClubDatabase(application.applicationContext).clubDao()
.getEventsByClubIdAfterDate(CURRENT_CLUB_ID, tomorrow)
}
}
EventAdapter
class EventAdapter(
private var dataSet: Array<Event>?,
private val onEventItemClickListener: OnEventItemClickListener
) : RecyclerView.Adapter<EventAdapter.EventViewHolder>() {
class EventViewHolder(val view: View) : RecyclerView.ViewHolder(view)
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): EventViewHolder {
val view =
LayoutInflater.from(parent.context).inflate(R.layout.event_item_layout, parent, false)
return EventViewHolder(view)
}
override fun onBindViewHolder(holder: EventViewHolder, position: Int) {
// show the item & add onEventItemClickListener for updating
}
fun setData(new: Array<Event>) {
this.dataSet = new
this.notifyDataSetChanged()
}
override fun getItemCount(): Int {
return dataSet?.size ?: 0
}
}
Database
#Database(
entities = [Event::class, Member::class, RequiredMembersForEvents::class, AttendedMembersForEvents::class],
version = 9,
exportSchema = false
)
#TypeConverters(Converters::class)
abstract class ClubDatabase : RoomDatabase() {
abstract fun clubDao(): ClubDao
companion object {
#Volatile
private var INSTANCE: ClubDatabase? = null
fun getClubDatabase(context: Context): ClubDatabase {
return INSTANCE ?: synchronized(this) {
val instance = INSTANCE
return if (instance != null) {
instance
} else {
Room.databaseBuilder(
context.applicationContext,
ClubDatabase::class.java,
"club-db"
)
.allowMainThreadQueries()
.fallbackToDestructiveMigration()
.build()
}
}
}
}
}
DAO
#Dao
interface ClubDao {
#Query("SELECT * FROM events WHERE clubId = :clubId AND dateTimeFrom > :date ORDER BY dateTimeFrom ASC")
fun getEventsByClubIdAfterDate(clubId: String, date: Date): LiveData<List<Event>>
// the rest of the DAO
}
Check your database singleton implementation, since variable INSTANCE there - is always null. You should set it at first time when you've got the instance of the class. Otherwise your app has a deal with different instances of your Database class.
Probably that causes a problem, when though some changes were made to database, but LiveData's observer for these changes was not triggered.