Im having trouble understanding why the expiryDate value of the flow from Datastore is always null. checkExpiry() is used to determine a navigation route and is only used in the viewmodel (there are no observers in the active fragment).
Any assistance is appreciated.
ViewModel
#HiltViewModel
class MyViewModel
#Inject
constructor(
private val userPreferences: UserPreferences,
private val savedSate: SavedStateHandle
) : ViewModel() {
private val expiryTimestamp = userPreferences.expiryTimestampFlow.asLiveData()
private fun checkExpiry(): Boolean {
val calendar = Calendar.getInstance()
return (calendar.timeInMillis > expiryTimestamp.value!!)
}
DataStore
#Singleton
class UserPreferences
#Inject
constructor(#ApplicationContext context: Context) {
private val Context.dataStore by preferencesDataStore("user_preferences")
private val dataStore = context.dataStore
//Preferences keys
private object PreferencesKeys {
val EXPIRY_TIMESTAMP = longPreferencesKey("expiryTimeStamp")
}
//Get Functions
val expiryTimestampFlow = dataStore.data
.catch { exception ->
if (exception is IOException) {
Log.e(TAG, "Error reading expiry date", exception)
emit(emptyPreferences())
} else {
throw exception
}
}
.map { preferences ->
preferences[PreferencesKeys.EXPIRY_TIMESTAMP] ?: 1672491600000
}
The LiveData in your ViewModel is not active. You activate it like this:
private val expiryTimestamp = userPreferences.expiryTimestampFlow.asLiveData(viewModelScope.coroutineContext)
Edit:
If you call your checkExpiry() function when the flow from the DataStore has not emitted a value yet (because it has to do some IO), you can get null in the LiveData.
As you are not observing this value from an activity or fragment, you don't need LiveData. You can query the DataStore like this:
private suspend fun checkExpiry(): Boolean {
val calendar = Calendar.getInstance()
return (calendar.timeInMillis > userPreferences.expiryTimestampFlow.first())
}
Related
I am trying to sort datas which are fetched from firebase realtime database according to the value of a child using MVVM architecture the daabase reference is created in a repository
GroupNoticeRepository
class GroupNoticeRepository(private var groupSelected: String) {
val auth = Firebase.auth
val user = auth.currentUser!!.uid
private val scheduleReference: DatabaseReference =
FirebaseDatabase.getInstance().getReference("group-notice").child(groupSelected)
#Volatile
private var INSTANCE: GroupNoticeRepository? = null
fun getInstance(): GroupNoticeRepository {
return INSTANCE ?: synchronized(this) {
val instance = GroupNoticeRepository(groupSelected)
INSTANCE = instance
instance
}
}
fun loadSchedules(allSchedules: MutableLiveData<List<GroupNoticeData>>) {
scheduleReference.addValueEventListener(object : ValueEventListener {
override fun onDataChange(snapshot: DataSnapshot) {
try {
val scheduleList: List<GroupNoticeData> =
snapshot.children.map { dataSnapshot ->
dataSnapshot.getValue(GroupNoticeData::class.java)!!
}
allSchedules.postValue(scheduleList)
} catch (_: Exception) {
}
}
override fun onCancelled(error: DatabaseError) {
}
})
}
}
GroupNoticeFragment
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
recycler = binding.taskList
recycler.layoutManager = LinearLayoutManager(context)
recycler.setHasFixedSize(true)
adapter = GroupNoticeAdapter(_inflater)
recycler.adapter = adapter
viewModel = ViewModelProvider(this)[GroupNoticeViewModel::class.java]
viewModel.initialize(groupId)
viewModel.allSchedules.observe(viewLifecycleOwner) {
adapter!!.updateUserList(it)
}
}
GroupNoticeViewModel
class GroupNoticeViewModel : ViewModel() {
private lateinit var repository: GroupNoticeRepository
private val _allSchedules = MutableLiveData<List<GroupNoticeData>>()
val allSchedules: LiveData<List<GroupNoticeData>> = _allSchedules
fun initialize(groupSelected: String) {
repository = GroupNoticeRepository(groupSelected).getInstance()
repository.loadSchedules(_allSchedules)
}
}
`
As you can see the current structure
group-notice
-groupId(groups)
-noticeId (notices)
- taskDate
Here under group notice there are some groups and in each group there are some notices(noticeId) .
Each notice has a task date . Now I am trying to sort the notices according to the taskdate meaning the taskDate which will is closer to todays date will view first in the recycler view. Or the notice with latest taskdate given will appear first in the recycler view .
Just as hassan bazai said I followed the same concept of comparing two dates
class FirebaseDataComparator : Comparator<GroupNoticeData?> {
override fun compare(p0: GroupNoticeData?, p1: GroupNoticeData?): Int {
val dateFormat = SimpleDateFormat("dd/MM/yyyy")
val firstDate: Date = dateFormat.parse(p0?.taskdate!!) as Date
val secondDate: Date = dateFormat.parse(p1?.taskdate!!) as Date
return firstDate.compareTo(secondDate)
}
}
Here groupNoticeData is the data class I am using to populate the data in my recycler View and took two objects of them . Parsed their date format accordingly and later on compared them.
And in the recyclerViewAdapter before adding my data, I sorted them using the comparator class and added them later on. Here is the part where I had to use the comparator class.
fun updateNoticeList(notices: List<GroupNoticeData>) {
Collections.sort(notices, FirebaseDataComparator())
this.tasks.clear()
this.tasks.addAll(notices)
notifyDataSetChanged()
}
I have a issue in getting a list returned in observe event in my activity. i am developing a login screen in MVVM. viewmodel is as follows.
my problem is i can get returned data in observe call back into a UI control. but same data returned assign into a list variable is empty. in other words, list returned unable to pass into a a list variable in an activity.
class LoginViewModel #Inject internal constructor (private val loginRepository: LoginRepository,private val usersRepository: UsersRepository): ViewModel() {
private var _userEmail:MutableLiveData<String>
private var _userPassword:MutableLiveData<String>
private var _userLoginData:MutableLiveData<UserLoginData>
private var allUsers:MutableLiveData<List<Users>>
private var findUser:MutableLiveData<List<Users>>
init{
_userEmail= MutableLiveData()
_userPassword= MutableLiveData()
_userLoginData= MutableLiveData()
allUsers= MutableLiveData()
findUser= MutableLiveData()
}
fun getEmail():LiveData<String>{
return _userEmail
}
fun getPassword():MutableLiveData<String>{
return _userPassword
}
fun userLogin(userEmail:String,userPassword:String):MutableLiveData<UserLoginData>{
_userEmail.postValue(userEmail)
_userPassword.postValue(userPassword)
viewModelScope.launch(Dispatchers.IO) {
var userlogindata:UserLoginData=loginRepository.userLogin(userEmail,userPassword)
_userLoginData.postValue(userlogindata)
}
return _userLoginData
}
fun getAllUsers():MutableLiveData<List<Users>>{
//lateinit var _allUsers:List<Users>
viewModelScope.launch(Dispatchers.IO) {
val _allUsers:List<Users> =usersRepository.getUsers()
allUsers.postValue(_allUsers)
}
return allUsers
}
fun findUser(userEmail:String):MutableLiveData<List<Users>>{
//lateinit var finduser:List<Users>
viewModelScope.launch(Dispatchers.IO) {
val _findUser:List<Users> =usersRepository.findUser(userEmail)
findUser.postValue(_findUser)
}
return findUser
}
}
in an activity i am observing the users list and getting the list into a list variable in the activity. code in the activity:
class MainActivity : AppCompatActivity() {
private lateinit var binding: ActivityMainBinding
private lateinit var loginViewModel: LoginViewModel
lateinit var loginData:UserLoginData
var users:List<Users> = emptyList()
var findUser:List<Users> = emptyList()
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
binding = ActivityMainBinding.inflate(layoutInflater)
setContentView(binding.root)
loginViewModel = ViewModelProvider(this).get(LoginViewModel::class.java)
/*observe users list*/
loginViewModel.getAllUsers().observe(this, {It->
users=It
binding.textView.text=It[0].email.toString()
})
loginViewModel.findUser(binding.loginEditTextTextEmailAddressTxt.toString().trim()).observe(this,{it->
findUser=it
})
This program failed if i use data in the users or findUser lists.
Kindly help me to find the best practice in getting the changed data from viewmodel into an activity
ViewModel:
data class User(
var name: String
)
private val _allUsers = MutableLiveData<List<User>>()
private val allUsers: LiveData<List<User>> get() = _allUsers
fun fetchAllUsers(): LiveData<List<User>> {
viewModelScope.launch {
//delay is simulating network request delay
delay(1000)
//listOf is simulating usersRepository.getUsers()
_allUsers.value = listOf(User("name1"), User("name2"), User("name3"))
}
return allUsers
}
Fragment:
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
viewModel.fetchAllUsers().observe(viewLifecycleOwner) { userList ->
userList.forEach {
Log.d("user", it.name)
}
}
You can try this way but I do not prefer returning liveData with function because you have to observe liveData once. You need to be careful observe once.
We have been discussing about this but we don't know the reason of creating a viewmodel factory to create a viewmodel instead of instantiate the viewmodel directly. What is the gain of creating a factory that just creates the viewmodel?
I just put a simple example of how I did it without Factory
here is the kodein module:
val heroesRepositoryModel = Kodein {
bind<HeroesRepository>() with singleton {
HeroesRepository()
}
bind<ApiDataSource>() with singleton {
DataModule.create()
}
bind<MainViewModel>() with provider {
MainViewModel()
}
}
The piece of the Activity where I instantiate the viewmodel without using the factory
class MainActivity : AppCompatActivity() {
private lateinit var heroesAdapter: HeroAdapter
private lateinit var viewModel: MainViewModel
private val heroesList = mutableListOf<Heroes.MapHero>()
private var page = 0
private var progressBarUpdated = false
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
viewModel = ViewModelProviders.of(this)
.get(MainViewModel::class.java)
initAdapter()
initObserver()
findHeroes()
}
The ViewModel where I instantiate the usecase directly without having it in the constructor
class MainViewModel : ViewModel(), CoroutineScope {
private val heroesRepository: HeroesRepository = heroesRepositoryModel.instance()
val data = MutableLiveData<List<Heroes.MapHero>>()
private var job: Job = Job()
override val coroutineContext: CoroutineContext
get() = uiContext + job
fun getHeroesFromRepository(page: Int) {
launch {
try {
val response = heroesRepository.getHeroes(page).await()
data.value = response.data.results.map { it.convertToMapHero() }
} catch (e: HttpException) {
data.value = null
} catch (e: Throwable) {
data.value = null
}
}
}
override fun onCleared() {
super.onCleared()
job.cancel()
}
}
So here a example using factory
class ListFragment : Fragment(), KodeinAware, ContactsAdapter.OnContactListener {
override val kodein by closestKodein()
private lateinit var adapterContacts: ContactsAdapter
private val mainViewModelFactory: MainViewModelFactory by instance()
private val mainViewModel: MainViewModel by lazy {
activity?.run {
ViewModelProviders.of(this, mainViewModelFactory)
.get(MainViewModel::class.java)
} ?: throw Exception("Invalid Activity")
}
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
return inflater.inflate(R.layout.fragment_list, container, false)
}
The viewmodelfactory:
class MainViewModelFactory (private val getContacts: GetContacts) : ViewModelProvider.Factory {
override fun <T : ViewModel?> create(modelClass: Class<T>): T {
if (modelClass.isAssignableFrom(MainViewModel::class.java)) {
return MainViewModel(getContacts) as T
}
throw IllegalArgumentException("Unknown ViewModel class")
}
}
And the viewmodel:
class MainViewModel(private val getContacts: GetContacts) : BaseViewModel() {
lateinit var gamesList: LiveData<PagedList<Contact>>
var contactsSelectedData: MutableLiveData<List<Contact>> = MutableLiveData()
var contactsSelected: ArrayList<Contact> = ArrayList()
private val pagedListConfig by lazy {
PagedList.Config.Builder()
.setEnablePlaceholders(false)
.setInitialLoadSizeHint(PAGES_CONTACTS_SIZE)
.setPageSize(PAGES_CONTACTS_SIZE)
.setPrefetchDistance(PAGES_CONTACTS_SIZE*2)
.build()
}
Here is the complete first example:
https://github.com/ibanarriolaIT/Marvel/tree/mvvm
And the complete second example:
https://github.com/AdrianMeizoso/Payment-App
We can not create ViewModel on our own. We need ViewModelProviders utility provided by Android to create ViewModels.
But ViewModelProviders can only instantiate ViewModels with no arg constructor.
So if I have a ViewModel with multiple arguments, then I need to use a Factory that I can pass to ViewModelProviders to use when an instance of MyViewModel is required.
For example -
public class MyViewModel extends ViewModel {
private final MyRepo myrepo;
public MyViewModel(MyRepo myrepo) {
this.myrepo = myrepo;
}
}
To instantiate this ViewModel, I need to have a factory which ViewModelProviders can use to create its instance.
ViewModelProviders Utility can not create instance of a ViewModel with argument constructor because it does not know how and what objects to pass in the constructor.
In short,
if we need to pass some input data to the constructor of the viewModel , we need to create a factory class for viewModel.
Like example :-
class MyViewModelFactory constructor(private val repository: DataRepository): ViewModelProvider.Factory {
override fun <T : ViewModel> create(modelClass: Class<T>): T {
return if (modelClass.isAssignableFrom(MyViewModel::class.java!!)) {
MyViewModel(this.repository) as T
} else {
throw IllegalArgumentException("ViewModel Not Found")
}
}
}
Reason
We cannot directly create the object of the ViewModel as it would not be aware of the lifecyclerOwner. So we use :-
ViewModelProviders.of(this, MyViewModelFactory(repository)).get(MyViewModel::class.java)
We have been discussing about this but we don't know the reason of creating a viewmodel factory to create a viewmodel instead of instantiate the viewmodel directly. What is the gain of creating a factory that just creates the viewmodel?
Because Android will only give you a new instance if it's not yet created for that specific given ViewModelStoreOwner.
Let's also not forget that ViewModels are kept alive across configuration changes, so if you rotate the phone, you're not supposed to create a new ViewModel.
If you are going back to a previous Activity and you re-open this Activity, then the previous ViewModel should receive onCleared() and the new Activity should have a new ViewModel.
Unless you're doing that yourself, you should probably just trust the ViewModelProviders.Factory to do its job.
(And you need the factory because you typically don't just have a no-arg constructor, your ViewModel has constructor arguments, and the ViewModelProvider must know how to fill out the constructor arguments when you're using a non-default constructor).
When we are simply using ViewModel, we cannot pass arguments to that ViewModel
class GameViewModel() : ViewModel() {
init {
Log.d(TAG, "GameViewModel created")
}
}
However, in some cases, we need to pass our own arguments to ViewModel. This can be done using ViewModelFactory.
class ScoreViewModel(finalScore: Int) : ViewModel() {
val score = finalScore
init {
Log.d(TAG, "Final score: $finalScore")
}
}
And to instantiate this ViewModel, we need a ViewModelProvider.Factory as simple ViewModel cannot instantiate it.
class ScoreViewModelFactory(private val finalScore: Int) : ViewModelProvider.Factory {
override fun <T : ViewModel?> create(modelClass: Class<T>): T {
if (modelClass.isAssignableFrom(ScoreViewModel::class.java)) {
return ScoreViewModel(finalScore) as T
}
throw IllegalArgumentException("Unknown ViewModel class")
}
}
When it comes to instantiating object of this ViewModel i.e with ViewModelProvider, we pass ViewModelFactory as an argument which contains information about our custom arguments which we want to pass. It goes like:
viewModelFactory = ScoreViewModelFactory(score)
viewModel = ViewModelProvider(this,viewModelFactory).get(ScoreViewModel::class.java)
That is why factory methods are there.
i'm trying to create a component that stream data from remote service continuously. The component starts and stops according to spring container lifecycle. I'm not sure how to test this component as the subscription is done inside my component so i was wondering wether this is the correct way to implement this kind of component with webflux or not. Does anybody know any similar component in any framework from where i might take some ideas?
Regards
class StreamingTaskAdapter(
private val streamEventsUseCase: StreamEventsUseCase,
private val subscriptionProperties: subscriptionProperties,
) : SmartLifecycle, DisposableBean, BeanNameAware {
private lateinit var disposable: Disposable
private var running: Boolean = false
private var beanName: String = "StreamingTaskAdapter"
private val logger = KotlinLogging.logger {}
override fun start() {
logger.info { "Starting container with name $beanName" }
running = true
doStart()
}
private fun doStart() {
disposable = Mono.just(
CreateSubscriptionCommand(
subscriptionProperties.events,
subscriptionProperties.owningApplication
)
)
.flatMap(streamEventsUseCase::createSubscription)
.flatMap { subscription ->
Mono.just(subscription)
.map(::ConsumeSubscriptionCommand)
.flatMap(streamEventsUseCase::consumeSubscription)
}
.repeat()
.retryWhen(Retry.backoff(MAX_ATTEMPTS, Duration.ofSeconds(2)).jitter(0.75))
.doOnSubscribe { logger.info { "Started event streaming" } }
.doOnTerminate { logger.info { "Stopped event streaming" } }
.subscribe()
}
override fun stop() {
logger.info("Stopping container with name $beanName")
doStop()
}
override fun isRunning(): Boolean = running
private fun doStop() {
running = false
disposable.dispose()
}
override fun destroy() {
logger.info("Destroying container with name $beanName")
doStop()
}
override fun setBeanName(name: String) {
this.beanName = name
}
companion object {
const val MAX_ATTEMPTS: Long = 3
}
}
I am trying to update my view according to my data in my ViewModel, using MVVM
I need in the method onCacheReception to update my map whenever zones is changing
ViewModel
class MainViewModel constructor(application: Application) : AndroidViewModel(application),
CacheListener {
private val instance = Initializer.getInstance(application.applicationContext)
private val _zones = MutableLiveData<List<Zone>>()
val zones: LiveData<List<Zone>>
get() = _zones
init {
CacheDispatcher.addCacheListener(this)
}
override fun onCacheReception() {
val zonesFromDB: List<Zone>? = instance.fetchZonesInDatabase()
_zones.value = zonesFromDB
}
}
MainActivity
class MainActivity : AppCompatActivity(), EasyPermissions.PermissionCallbacks, OnMapReadyCallback {
private val mainViewModel: MainViewModel = ViewModelProvider(this).get(MainViewModel(application)::class.java)
private lateinit var initializer: Initializer
private lateinit var map: GoogleMap
private val REQUEST_CODE_LOCATIONS: Int = 100
private val permissionLocationsRationale: String = "Permissions for Fine & Coarse Locations"
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
if (checkForLocationsPermission()) {
setUp()
mapSetUp()
}
mainViewModel.zones.observe(this, Observer { zones ->
zones.forEach {
Log.i("YES DATA", "Data has been updated")
val latLng = it.lat?.let { it1 -> it.lng?.let { it2 -> LatLng(it1, it2) } }
val markerOptions = latLng?.let { it1 -> MarkerOptions().position(it1) }
map.addMarker(markerOptions)
}
})
}
My Log is never displaying and it doesn't seem while debugging that mainView.zones.observe { } is called when I receive some new data in my ViewModel
In the onCacheReception(), replace:
_zones.value = zonesFromDB
by:
_zones.postValue(zonesFromDB)
in case your onCacheReception() function is called from a worker thread.