Develop Reference

Why not auto update list when used LiveData in Android

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.

LiveData with condition

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

Room not updating entities with #Update(onConflict = OnConflictStrategy.REPLACE)

My application uses Google Places API which data I later use to get weather from openweather.
I have a SearchFragment with RecyclerView where this happens.
Inside SearchFragment I observe the list I'm getting:
viewModel.predictions.observe(viewLifecycleOwner) {
citiesAdapter.submitList(it)
}
<...>
override fun onCreateOptionsMenu(menu: Menu, inflater: MenuInflater) {
inflater.inflate(R.menu.menu_fragment_weather, menu)
<...>
searchView.onQueryTextChanged {
viewModel.searchQuery.value = it
}
}
My viewModel:
class SearchViewModel #Inject constructor(
private val repository: AutocompleteRepository,
private val weatherRepository: WeatherRepository
) : ViewModel() {
fun provideClient(client: PlacesClient) {
repository.provideClient(client)
}
val searchQuery = MutableStateFlow("")
private val autocompleteFlow = searchQuery.flatMapLatest {
repository.getPredictions(it)
}
val predictions = autocompleteFlow.asLiveData()
fun onAddPlace(place: PlacesPrediction, added: Boolean) {
viewModelScope.launch {
repository.update(place, added)
if (added) weatherRepository.addWeather(place)
else weatherRepository.delete(place)
}
}
fun onDestroy() = viewModelScope.launch {repository.clearDb()}
}
Inside adapter I bind my items like this:
inner class CityViewHolder(private val binding: ItemCityToAddBinding) : RecyclerView.ViewHolder(binding.root) {
init {
binding.apply {
btnAdd.setOnClickListener {
val position = adapterPosition
if (position != RecyclerView.NO_POSITION) {
val place = getItem(position)
btnAdd.animate().rotation(if (place.isAdded) 45f else 0f).start()
println("Current item state (isAdded): ${place.isAdded}")
listener.onAddClick(place, !place.isAdded)
}
}
}
}
fun bind(prediction : PlacesPrediction) {
binding.apply {
val cityName = prediction.fullText.split(", ")[0]
locationName.text = cityName
fullName.text = prediction.fullText
btnAdd.animate().rotation(if (prediction.isAdded) 45f else 0f).start()
}
}
}
Where listener is passed to my adapter as a parameter from my fragment:
override fun onAddClick(place: PlacesPrediction, isAdded: Boolean) {
viewModel.onAddPlace(place, isAdded)
println("Parameter passed to onClick: $isAdded, placeId = ${place.placeId}")
}
<...>
val citiesAdapter = CitiesAdapter(this)
My repository's update() method looks like this:
suspend fun update(place: PlacesPrediction, added: Boolean) =
database.dao().update(place.copy(isAdded = added))
And finally, my dao's update:
#Update(onConflict = OnConflictStrategy.REPLACE)
suspend fun update(prediction: PlacesPrediction)
This is all tied up on PlacesPrediction class, an here it is:
#Entity(tableName = "autocomplete_table")
data class PlacesPrediction(
val fullText: String,
val latitude: Double,
val longitude: Double,
val placeId: String,
val isAdded: Boolean = false
) {
#PrimaryKey(autoGenerate = true) var id: Int = 0
}
So, my problem is that PlacesPredictions entries in my database are not getting updated. Actually, the only field I want to update with the code provided above is isAdded, but it stays the same after I press btnAdd of my list item. I used Android Studio's Database Inspector to verify that.
I tried using #Insert instead like so:
#Insert(onConflict = OnConflictStrategy.REPLACE)
suspend fun insert(prediction: PlacesPrediction)
suspend fun update(place: PlacesPrediction, added: Boolean) =
database.dao().insert(place.copy(isAdded = added))
But strangely it only inserts a copy of place, the original item I clicked on stays the same.
Workaround
I get the desired behavior only if I hack my way to it:
#Entity(tableName = "autocomplete_table")
data class PlacesPrediction(
val fullText: String,
val latitude: Double,
val longitude: Double,
val placeId: String,
var isAdded: Boolean = false,
#PrimaryKey(autoGenerate = true) var id: Int = 0
)
suspend fun update(place: PlacesPrediction, added: Boolean) =
database.dao().insert(place.copy(isAdded = added, id = place.id))
And I don't like this soution at all. So my question is: how do I make #Update work?

As you probably already understood, the generated copy method of data classes ignores all members declared outside the constructor. So place.copy(isAdded = added) will generate a copy of all constructor parameters, but leave the id as the default 0, meaning a new element should be inserted, instead of updating an existing one.
Now this is my personal opinion:
Having the id as constructor parameter is the most elegant solution, as updates will work out of the box.
However if you dislike it that much, maybe an extension function might help you:
inline fun PlacesPrediction.preserveId(copyBuilder: PlacesPrediction.() -> PlacesPrediction): PlacesPrediction{
val copy = copyBuilder(this)
copy.id = this.id
return copy
}
//usage
suspend fun update(place: PlacesPrediction, added: Boolean) =
database.dao().insert(place.preserveId { copy(isAdded = added) })

How to get an id of an added object from an Activity(VIEW) in a database(MODEL) through VIEWMODEL | Android, MVVM

I have a ShoppingList App that is built on MVVM architecture Android.
I did not make it, but I followed a tutorial on Youtube.
This is the image of the app(1/2) where the shopping list is shown. The bottom right side is a button for adding new elements of the list.
This is the second view(2/2) where the dialog appears to enter a name of our element and amount of it. Here we have cancel button and add button.
The problem is when I click the ADD button on the Dialog Box I do not know how to get an ID of this added item to the recycler view on my VIEW and to make it appear via the TOAST command on my main Activity.
The question is - How to get an ID of a new added element to my shopping list and show it on my MainActivity(ShoppingActivity) VIEW when I click the ADD button?
If you need additional information ask me out immediately! I will provide you anything you need.
Code is provided here:
ShoppingActivity(View)
class ShoppingActivity : AppCompatActivity(), KodeinAware {
override val kodein by kodein()
private val factory: ShoppingViewModelFactory by instance()
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_shopping)
// View Model is being created out of other classes to set changes to View
val viewModel = ViewModelProviders.of(this, factory).get(ShoppingViewModel::class.java)
// Adapters and Recycler View
val adapter = ShoppingItemAdapter(listOf(), viewModel)
rvShoppingItems.layoutManager = LinearLayoutManager(this)
rvShoppingItems.adapter = adapter
// ViewModel makes changes to the Activity
viewModel.getAllShoppingItems().observe(this, Observer {
adapter.items = it
adapter.notifyDataSetChanged()
})
fab.setOnClickListener {
AddShoppingItemDialog(this ,
object: AddDialogListener{
override fun onAddButtonClicked(item: ShoppingItem) {
viewModel.upsert(item)
showToast(viewModel.getID(item).toString().toInt())
}
}).show()
}
}
fun showToast(id: Int) {
Toast.makeText(this#ShoppingActivity, "ID записи: $id", Toast.LENGTH_LONG).show()
}}
ShoppingViewModel(ViewModel)
class ShoppingViewModel(private val repository: ShoppingRepository): ViewModel() {
fun upsert(item: ShoppingItem) = CoroutineScope(Dispatchers.IO).launch {
repository.upsert(item)
}
fun delete(item: ShoppingItem) = CoroutineScope(Dispatchers.IO).launch {
repository.delete( item)
}
fun getID(item: ShoppingItem) = repository.getID(item)
fun getAllShoppingItems() = repository.getAllShoppingItems()
}
AddShoppingItemDialog(the logic of showing Dialog info)
class AddShoppingItemDialog(context: Context, var addDialogListener: AddDialogListener): AppCompatDialog(context) {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.dialog_add_shopping_item)
tvAdd.setOnClickListener {
val name = etName.text.toString()
val amount = etAmount.text.toString()
if(name.isEmpty()) {
Toast.makeText(context, "Please enter the name", Toast.LENGTH_LONG).show()
return#setOnClickListener
}
if(amount.isEmpty()) {
Toast.makeText(context, "Please enter the amount", Toast.LENGTH_LONG).show()
return#setOnClickListener
}
val item = ShoppingItem(name, amount.toInt())
// We need to
addDialogListener.onAddButtonClicked(item)
dismiss()
}
tvCancel.setOnClickListener {
cancel()
}
}}
Repository
class ShoppingRepository(private val db: ShoppingDatabase) {
suspend fun upsert(item: ShoppingItem) = db.getShoppingDao().upsert(item)
suspend fun delete(item: ShoppingItem) = db.getShoppingDao().delete(item)
fun getID(item: ShoppingItem) = db.getShoppingDao().getID(item)
fun getAllShoppingItems() = db.getShoppingDao().getAllShoppingItems()}
ShoppingDAO
#Dao
interface ShoppingDao {
#Insert(onConflict = OnConflictStrategy.REPLACE)
suspend fun upsert(item: ShoppingItem) : Long
#Delete
suspend fun delete(item: ShoppingItem)
#Query("SELECT * FROM shopping_items WHERE id = $CURRENT_POSITION")
fun getID(item: ShoppingItem): LiveData<Int>
#Query("SELECT * FROM shopping_items")
fun getAllShoppingItems(): LiveData<List<ShoppingItem>>
}
ShoppingItem
const val CURRENT_POSITION = 0
#Entity(tableName = "shopping_items")
data class ShoppingItem(
#ColumnInfo(name = "item_name")
var name: String,
#ColumnInfo(name = "item_amount")
var amount: Int
) {
#PrimaryKey(autoGenerate = true)
var id: Int? = CURRENT_POSITION
}
AddDialogListener
interface AddDialogListener {
fun onAddButtonClicked(item: ShoppingItem)
}
App View with added items

Since insert/upsert operations on Database are suspend functions, observe returned id in view model
In ShoppingViewModel
private var _itemId : Long = MutableLiveData<Long>()
val itemId : LiveData<Long>
get() = _itemId
fun upsert(item: ShoppingItem) = CoroutineScope(Dispatchers.IO).launch {
val id = repository.upsert(item)
_itemId.postValue(id)
}
In ShoppingActivity,
viewModel.itemId.observe(this, Observer {id ->
showToast(id)
})
Please let me know if you need to know more details.

You need to use SingleLiveEvent to observe the value only once.
Add this SingleLiveEvent class
/**
* A lifecycle-aware observable that sends only new updates after subscription, used for events like
* navigation and Snackbar messages.
*
*
* This avoids a common problem with events: on configuration change (like rotation) an update
* can be emitted if the observer is active. This LiveData only calls the observable if there's an
* explicit call to setValue() or call().
*
*
* Note that only one observer is going to be notified of changes.
*/
class SingleLiveEvent<T> : MutableLiveData<T>() {
private val mPending = AtomicBoolean(false)
#MainThread
override fun observe(owner: LifecycleOwner, observer: Observer<in T>) {
if (hasActiveObservers()) {
Log.w(TAG, "Multiple observers registered but only one will be notified of changes.")
}
// Observe the internal MutableLiveData
super.observe(owner, Observer { t ->
if (mPending.compareAndSet(true, false)) {
observer.onChanged(t)
}
})
}
#MainThread
override fun setValue(t: T?) {
mPending.set(true)
super.setValue(t)
}
/**
* Used for cases where T is Void, to make calls cleaner.
*/
#MainThread
fun call() {
value = null
}
companion object {
private val TAG = "SingleLiveEvent"
}
}
In ShoppingViewModel
Replace this
private var _itemId : Long = MutableLiveData<Long>()
val itemId : LiveData<Long>
get() = _itemId
with
private var _itemId : Long = SingleLiveEvent<Long>()
val itemId : LiveData<Long>
get() = _itemId
You can use Event wrapper when there are more than one observer.
For more details:
https://medium.com/androiddevelopers/livedata-with-snackbar-navigation-and-other-events-the-singleliveevent-case-ac2622673150

How to use SearchView with LiveData and ViewModel in Room

i want to use SearchView for search some element in room db and i have a problem with this because i cant use getFilter in RecyclerViewAdapter because i have ViewModel maybe whoes know how to combine all of this element in one project.
I search one way use Transormations.switchMap. But I couldn’t connect them.
ProductViewModel
class ProductViewModel(application: Application) : AndroidViewModel(application) {
private val repository: ProductRepository
val allProducts: LiveData<List<ProductEntity>>
private val searchStringLiveData = MutableLiveData<String>()
init {
val productDao = ProductsDB.getDatabase(application, viewModelScope).productDao()
repository = ProductRepository(productDao)
allProducts = repository.allProducts
searchStringLiveData.value = ""
}
fun insert(productEntity: ProductEntity) = viewModelScope.launch {
repository.insert(productEntity)
}
val products = Transformations.switchMap(searchStringLiveData) { string ->
repository.getAllListByName(string)
}
fun searchNameChanged(name: String) {
searchStringLiveData.value = name
}
}
ProductDao
interface ProductDao {
#Insert(onConflict = OnConflictStrategy.IGNORE)
suspend fun insertProduct(productEntity: ProductEntity)
#Query("SELECT * from products")
fun getListAllProducts(): LiveData<List<ProductEntity>>
#Query("DELETE FROM products")
suspend fun deleteAll()
#Query("SELECT * FROM products where product_name_ent LIKE :name or LOWER(product_name_ent) like LOWER(:name)")
fun getListAllByName(name: String):LiveData<List<String>>
}

ProductDao
#Query("SELECT * FROM products where product_name_ent LIKE :name or LOWER(product_name_ent) like LOWER(:name)")
fun getListAllByName(name: String):LiveData<List<ProductEntity>>
This Method in your dao should return LiveData<List<ProductEntity>> and not LiveData<List<String>>, because this query selects everything (*) from the entity and not a specific column.
it is similar to (#Query("SELECT * from products") fun getListAllProducts():LiveData<List<ProductEntity>>)
ProductViewModel
class ProductViewModel(application: Application) : AndroidViewModel(application) {
private val repository: ProductRepository
init {
val productDao = ProductsDB.getDatabase(
application,
viewModelScope
).productDao()
repository = ProductRepository(productDao)
}
private val searchStringLiveData = MutableLiveData<String>("") //we can add initial value directly in the constructor
val allProducts: LiveData<List<ProductEntity>>=Transformations.switchMap(searchStringLiveData)
{
string->
if (TextUtils.isEmpty(string)) {
repository.allProducts()
} else {
repository.allProductsByName(string)
}
}
fun insert(productEntity: ProductEntity) = viewModelScope.launch {
repository.insert(productEntity)
}
fun searchNameChanged(name: String) {
searchStringLiveData.value = name
}
}
Repository
...with the other method that you have, add the following:
fun allProducts():LiveData<List<ProductEntity>>=productDao.getListAllProducts()
fun allProductsByNames(name:String):LiveData<List<ProductEntity>>=productDao.getListAllByName(name)
In Your Activity Or Fragment Where you have the recyclerview adapter
inside onCreate() (if it is an activity)
viewModel.allProducts.observe(this,Observer{products->
//populate your recyclerview here
})
or
onActivityCreated(if it is a fragment)
viewModel.allProducts.observe(viewLifecycleOwner,Observer{products->
//populate your recyclerview here
})
Now set a listener to the searchView, everytime the user submit the query , call viewModel.searchNameChanged(// pass the new value)
Hope this helps
Regards,