Develop Reference

LiveData not getting observed in case of set or post value

I am observing live data from the repository to view model but I am not getting any callback. Why is this so?
MyViewModel.kt
fun incrementPoints(userPoints: UserPoints): LiveData<NetworkResource<StatusResponse>> {
var callbackObserver = MutableLiveData<NetworkResource<StatusResponse>>()
IncrementPointsRepository.incrementPoints(userPoints).observeForever {
//not getting any callback here
callbackObserver.value = it
}
return callbackObserver
}
Repository.kt
object IncrementPointsRepository {
fun incrementPoints(userPoints: UserPoints): LiveData<NetworkResource<StatusResponse>> {
val callbackObserver = MutableLiveData<NetworkResource<StatusResponse>>()
val destinationService = ServiceBuilder.buildService(DestinationService::class.java)
val requestCall = destinationService.incrementPoints(userPoints)
requestCall.enqueue(object : Callback<StatusResponse> {
override fun onFailure(call: Call<StatusResponse>, t: Throwable) {
callbackObserver.value = NetworkResource.error(t)
}
override fun onResponse(call: Call<StatusResponse>, response: Response<StatusResponse>) {
//this is getting called
callbackObserver.value = NetworkResource.success(response)
}
})
return callbackObserver
}
}

incrementPoints function was called from another thread so it wasn't getting observed.
activity.runOnUiThread resolved this

UI is not updating while viewModel is updated in android kotlin

I am following the MVVM pattern Activity-->ViewModel ---> Repository . Repository is calling api and updated the LiveData. The value is of LiveData is also updated in ViewModel but its not reflecting on Activity. Please guide me where i am missing, Code is given below
Activity code:
class LoginWithEmailActivity : AppCompatActivity() {
private var loginViewModel: LoginViewModel? = null
private var binding: ActivityLoginWithEmailBinding? = null
private var btnLogin : Button? = null
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
loginViewModel = ViewModelProviders.of(this).get(LoginViewModel::class.java)
binding = DataBindingUtil.setContentView(this#LoginWithEmailActivity, R.layout.activity_login_with_email)
binding!!.setLifecycleOwner(this)
binding!!.setLoginViewModel(loginViewModel)
btnLogin = findViewById(R.id.btn_login)
loginViewModel!!.servicesLiveData!!.observe(this, Observer<LoginDataModel?> { serviceSetterGetter ->
val msg = serviceSetterGetter.success
Toast.makeText(this#LoginWithEmailActivity, ""+msg, Toast.LENGTH_SHORT).show()
Log.v("///LOGIN SUCCESS////",""+msg);
})
btnLogin!!.setOnClickListener {
loginViewModel!!.getUser()
}
}
ViewModel.kt
class LoginViewModel : ViewModel() {
var servicesLiveData: MutableLiveData<LoginDataModel>? = MutableLiveData()
fun getUser() {
servicesLiveData = MainActivityRepository.getServicesApiCall()
}
}
Repository.kt
object MainActivityRepository {
val serviceSetterGetter = MutableLiveData<LoginDataModel>()
fun getServicesApiCall(): MutableLiveData<LoginDataModel> {
val params = JsonObject()
params.addProperty("email", "xyz#gmail.com")
val call: Call<LoginDataModel> = ApiClient.getClient.getPhotos(params)
call.enqueue(object : Callback<LoginDataModel> {
#RequiresApi(Build.VERSION_CODES.N)
override fun onResponse(call: Call<LoginDataModel>?, response: Response<LoginDataModel>?) {
if (response != null) {
val data = response.body()
serviceSetterGetter?.postValue(data);
}
}
override fun onFailure(call: Call<LoginDataModel>?, t: Throwable?) {
}
})
return serviceSetterGetter
}
}

You subscribe to the LiveData in onCreate
loginViewModel!!.servicesLiveData!!.observe(this, Observer<LoginDataModel?> { serviceSetterGetter ->
val msg = serviceSetterGetter.success
Toast.makeText(this#LoginWithEmailActivity, ""+msg, Toast.LENGTH_SHORT).show()
Log.v("///LOGIN SUCCESS////",""+msg);
})
but then getUser creates a new reference
fun getUser() {
servicesLiveData = MainActivityRepository.getServicesApiCall()
}
The one you are subscribed to is not the same as the getUser liveData.
If you want to keep what you have mostly the same you need to use MediatorLiveData
Or just do
getUser().observe(this, Observer<LoginDataModel?> { serviceSetterGetter ->
val msg = serviceSetterGetter.success
Toast.makeText(this#LoginWithEmailActivity, ""+msg, Toast.LENGTH_SHORT).show()
Log.v("///LOGIN SUCCESS////",""+msg);
})
fun getUser(): LiveData<LoginDataModel> {
return MainActivityRepository.getServicesApiCall()
}

onResume does not worked in viewmodel

my data is fetched only when it is created...im using viewmodel...when press back button it doesnt update the previous data..onresume is not working in this...
i refered this but none of those helped--> Reacting to activity lifecycle in ViewModel
i need help
thanks in advance
activity:--
class MyAccount : BaseClassActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.myaccount)
var mActionBarToolbar = findViewById<androidx.appcompat.widget.Toolbar>(R.id.toolbartable);
setSupportActionBar(mActionBarToolbar);
setEnabledTitle()
val resetbutton=findViewById<Button>(R.id.resetpwd)
resetbutton.setOnClickListener {
val i=Intent(applicationContext,
ResetPasswordActivity::class.java)
startActivity(i)
}
val editbutton=findViewById<Button>(R.id.editdetail)
editbutton.setOnClickListener {
val i=Intent(applicationContext, EditProfile::class.java)
startActivity(i)
}
hello()
}
override fun onResume() {
super.onResume()
hello()
}
fun hello(){
val first_name = findViewById<TextView>(R.id.firstname)
val last_name = findViewById<TextView>(R.id.lastname)
val emailuser = findViewById<TextView>(R.id.emailuser)
val phone_no = findViewById<TextView>(R.id.phone_no)
val birthday = findViewById<TextView>(R.id.birthday)
val image=findViewById<ImageView>(R.id.imageprofile)
val model = ViewModelProvider(this)[MyAccountViewModel::class.java]
model.viewmodel?.observe(this, object : Observer<My_account_base_response> {
override fun onChanged(t: My_account_base_response?) {
first_name.setText(t?.data?.user_data?.first_name)
last_name.setText(t?.data?.user_data?.last_name)
emailuser.setText(t?.data?.user_data?.email)
phone_no.setText(t?.data?.user_data?.phone_no).toString()
birthday.setText(t?.data?.user_data?.dob).toString()
Glide.with(applicationContext).load(t?.data?.user_data?.profile_pic)
.diskCacheStrategy(DiskCacheStrategy.ALL)
.placeholder(R.drawable.ic_launcher_foreground)
.into(image)
}
})
}
override fun onOptionsItemSelected(item: MenuItem): Boolean {
return when (item.itemId) {
android.R.id.home -> {
NavUtils.navigateUpFromSameTask(this)
true
}
else -> super.onOptionsItemSelected(item)
}
}}
viewmodel:--
class MyAccountViewModel(context: Application) :AndroidViewModel(context),LifecycleObserver{
private var MyAccountViewModels: MutableLiveData<My_account_base_response>? = null
val viewmodel: MutableLiveData<My_account_base_response>?
get() {
if (MyAccountViewModels == null) {
MyAccountViewModels = MutableLiveData<My_account_base_response>()
loadviewmodel()
}
return MyAccountViewModels
}
private fun loadviewmodel(){
val token :String = SharedPrefManager.getInstance(getApplication()).user.access_token.toString()
RetrofitClient.instance.fetchUser(token)
.enqueue(object : Callback<My_account_base_response> {
override fun onFailure(call: Call<My_account_base_response>, t: Throwable) {
Log.d("res", "" + t)
}
override fun onResponse(
call: Call<My_account_base_response>,
response: Response<My_account_base_response>
) {
var res = response
if (res.body()?.status == 200) {
MyAccountViewModels!!.value = response.body()
} else {
try {
val jObjError =
JSONObject(response.errorBody()!!.string())
Toast.makeText(getApplication(),
jObjError.getString("user_msg"),
Toast.LENGTH_LONG).show()
} catch (e: Exception) {
Log.e("errorrr", e.message)
}
}
}
})
}}

There are bunch of things wrong here, so let me provide you refactored code and explanation as much as I would be able to..
Activity:
class MyAccount : BaseClassActivity() {
private val mActionBarToolbar by lazy { findViewById<androidx.appcompat.widget.Toolbar>(R.id.toolbartable) }
private val resetbutton by lazy { findViewById<Button>(R.id.resetpwd) }
private val editbutton by lazy { findViewById<Button>(R.id.editdetail) }
private val first_name by lazy { findViewById<TextView>(R.id.firstname) }
private val last_name by lazy { findViewById<TextView>(R.id.lastname) }
private val emailuser by lazy { findViewById<TextView>(R.id.emailuser) }
private val phone_no by lazy { findViewById<TextView>(R.id.phone_no) }
private val birthday by lazy { findViewById<TextView>(R.id.birthday) }
private val image by lazy { findViewById<ImageView>(R.id.imageprofile) }
lateinit var model: MyAccountViewModel
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.myaccount)
setSupportActionBar(mActionBarToolbar)
setEnabledTitle()
model = ViewModelProvider(this)[MyAccountViewModel::class.java]
resetbutton.setOnClickListener {
val i = Intent(applicationContext, ResetPasswordActivity::class.java)
startActivity(i)
}
editbutton.setOnClickListener {
val i = Intent(applicationContext, EditProfile::class.java)
startActivity(i)
}
model.accountResponseData.observe(this, object : Observer<My_account_base_response> {
override fun onChanged(t: My_account_base_response?) {
first_name.setText(t?.data?.user_data?.first_name)
last_name.setText(t?.data?.user_data?.last_name)
emailuser.setText(t?.data?.user_data?.email)
phone_no.setText(t?.data?.user_data?.phone_no).toString()
birthday.setText(t?.data?.user_data?.dob).toString()
Glide.with(applicationContext)
.load(t?.data?.user_data?.profile_pic)
.diskCacheStrategy(DiskCacheStrategy.ALL)
.placeholder(R.drawable.ic_launcher_foreground)
.into(image)
}
})
}
override fun onResume() {
super.onResume()
model.loadAccountData()
}
override fun onOptionsItemSelected(item: MenuItem): Boolean {
return when (item.itemId) {
android.R.id.home -> {
NavUtils.navigateUpFromSameTask(this)
true
}
else -> super.onOptionsItemSelected(item)
}
}
}
Few notes on your activity class:
You don't need to findViewById everytime, just do it once during onCreate or do it lazily. (FYI consider using kotlin synthetics or view binding or data binding)
Initialize your viewModel during onCreate method only. (That's the best way to do it)
Also observer your LiveData from ViewModel once, it should be also from the onCreate as it's the entry point to the activity and apart from config changes this method called only once. So, it's safe to observe it over there rather than during onResume which will be called multiple times during activity lifecycle. (The main issue your code wasn't working, so as a fix you only call your API method from ViewModel during resume)
ViewModel:
class MyAccountViewModel(context: Application) : AndroidViewModel(context) {
private val _accountResponseData = MutableLiveData<My_account_base_response?>()
val accountResponseData: MutableLiveData<My_account_base_response?>
get() = _accountResponseData
init {
loadAccountData()
}
fun loadAccountData() {
val token: String = SharedPrefManager.getInstance(getApplication()).user.access_token.toString()
RetrofitClient.instance.fetchUser(token)
.enqueue(object : Callback<My_account_base_response> {
override fun onFailure(call: Call<My_account_base_response>, t: Throwable) {
Log.d("res", "" + t)
_accountResponseData.value = null
}
override fun onResponse(
call: Call<My_account_base_response>,
response: Response<My_account_base_response>
) {
var res = response
if (res.body()?.status == 200) {
_accountResponseData.value = response.body()
} else {
try {
val jObjError =
JSONObject(response.errorBody()!!.string())
Toast.makeText(
getApplication(),
jObjError.getString("user_msg"),
Toast.LENGTH_LONG
).show()
} catch (e: Exception) {
Log.e("errorrr", e.message)
}
}
}
})
}
}
Don't make initial API call along with LiveData creation, it's okay to do in most of cases but if you're updating LiveData on response of that call then it's good to make it separately like during init block.
It's good practice not to allow Ui (Activity/Fragments) to modify LiveDatas of ViewModel directly. So, that's good sign you're following such pattern by having private MutableLiveData exposed as public LiveData, but do it correctly as suggested.
Side note: Your view model doesn't need to be LifecycleObserver. LifecycleObserver is used for some custom class/component which needs to be managed by their self by silently observing/depending on activity lifecycle independently. That's not the use case of ViewModel.
The only thing that I found why your code wasn't working correctly is because you were creating & observing ViewModel & LiveData over & over again as new objects from onResume method where you called hello() method.
Let me know if something don't make sense or missing.

Android: Firebase Object is null when using kotlin flow

My problem is, that when I try to get a document out of my database, that this document aka the object is always null. I only have this problem when I use Kotlin Coroutines to get the document out of my database. Using the standard approach with listeners do work.
EmailRepository
interface EmailRepository {
suspend fun getCalibratePrice(): Flow<EmailEntity?>
suspend fun getRepairPrice(): Flow<EmailEntity?>
}
EmailRepository Implementation
class EmailRepositoryImpl #Inject constructor(private val db: FirebaseFirestore) : EmailRepository {
fun hasInternet(): Boolean {
return true
}
// This works! When using flow to write a document, the document is written!
override fun sendEmail(email: Email)= flow {
emit(EmailStatus.loading())
if (hasInternet()) {
db.collection("emails").add(email).await()
emit(EmailStatus.success(Unit))
} else {
emit(EmailStatus.failed<Unit>("No Email connection"))
}
}.catch {
emit(EmailStatus.failed(it.message.toString()))
}.flowOn(Dispatchers.Main)
// This does not work! "EmailEntity" is always null. I checked the document path!
override suspend fun getCalibratePrice(): Flow<EmailEntity?> = flow {
val result = db.collection("emailprice").document("Kalibrieren").get().await()
emit(result.toObject<EmailEntity>())
}.catch {
}.flowOn(Dispatchers.Main)
// This does not work! "EmailEntity" is always null. I checked the document path!
override suspend fun getRepairPrice(): Flow<EmailEntity?> = flow {
val result = db.collection("emailprice").document("Reparieren").get().await()
emit(result.toObject<EmailEntity>())
}.catch {
}.flowOn(Dispatchers.Main)
}
Viewmodel where I get the data
init {
viewModelScope.launch {
withContext(Dispatchers.IO) {
if (subject.value != null){
when(subject.value) {
"Test" -> {
emailRepository.getCalibratePrice().collect {
emailEntity.value = it
}
}
"Toast" -> {
emailRepository.getRepairPrice().collect {
emailEntity.value = it
}
}
}
}
}
}
}
private val emailEntity = MutableLiveData<EmailEntity?>()
private val _subject = MutableLiveData<String>()
val subject: LiveData<String> get() = _subject
Fragment
#AndroidEntryPoint
class CalibrateRepairMessageFragment() : EmailFragment<FragmentCalibrateRepairMessageBinding>(
R.layout.fragment_calibrate_repair_message,
) {
// Get current toolbar Title and send it to the next fragment.
private val toolbarText: CharSequence by lazy { toolbar_title.text }
override val viewModel: EmailViewModel by navGraphViewModels(R.id.nav_send_email) { defaultViewModelProviderFactory }
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
// Here I set the data from the MutableLiveData "subject". I don't know how to do it better
viewModel.setSubject(toolbarText.toString())
}
}
One would say, that the Firebase rules are the problems here, but that should not be the case here, because the database is open and using the listener approach does work.
I get the subject.value from my CalibrateRepairMessageFragment. When I don't check if(subject.value != null) I get a NullPointerException from my init block.
I will use the emailEntitiy only in my viewModel and not outside it.
I appreciate every help, thank you.
EDIT
This is the new way I get the data. The object is still null! I've also added Timber.d messages in my suspend functions which also never get executed therefore flow never throws an error.. With this new approach I don't get a NullPointerException anymore
private val emailEntity = liveData {
when(subject.value) {
"Test" -> emailRepository.getCalibratePrice().collect {
emit(it)
}
"Toast" -> emailRepository.getRepairPrice().collect {
emit(it)
}
// Else block is never executed, therefore "subject.value" is either Test or toast and the logic works. Still error when using flow!
else -> EmailEntity("ERROR", 0F)
}
}
I check if the emailEntity is null or not with Timber.d("EmailEntity is ${emailEntity.value}") in one of my functions.
I then set the price with val price = MutableLiveData(emailEntity.value?.basePrice ?: 1000F) but because emailentity is null the price is always 1000
EDIT 2
I have now further researched the problem and made a big step forward. When observing the emailEntity from a fragment like CalibrateRepairMessageFragment the value is no longer null.
Furthermore, when observing emailEntity the value is also not null in viewModel, but only when it is observed in one fragment! So how can I observe emailEntity from my viewModel or get the value from my repository and use it in my viewmodel?

Okay, I have solved my problem, this is the final solution:
Status class
sealed class Status<out T> {
data class Success<out T>(val data: T) : Status<T>()
class Loading<T> : Status<T>()
data class Failure<out T>(val message: String?) : Status<T>()
companion object {
fun <T> success(data: T) = Success<T>(data)
fun <T> loading() = Loading<T>()
fun <T> failed(message: String?) = Failure<T>(message)
}
}
EmailRepository
interface EmailRepository {
fun sendEmail(email: Email): Flow<Status<Unit>>
suspend fun getCalibratePrice(): Flow<Status<CalibrateRepairPricing?>>
suspend fun getRepairPrice(): Flow<Status<CalibrateRepairPricing?>>
}
EmailRepositoryImpl
class EmailRepositoryImpl (private val db: FirebaseFirestore) : EmailRepository {
fun hasInternet(): Boolean {
return true
}
override fun sendEmail(email: Email)= flow {
Timber.d("Executed Send Email Repository")
emit(Status.loading())
if (hasInternet()) {
db.collection("emails").add(email).await()
emit(Status.success(Unit))
} else {
emit(Status.failed<Unit>("No Internet connection"))
}
}.catch {
emit(Status.failed(it.message.toString()))
}.flowOn(Dispatchers.Main)
// Sends status and object to viewModel
override suspend fun getCalibratePrice(): Flow<Status<CalibrateRepairPricing?>> = flow {
emit(Status.loading())
val entity = db.collection("emailprice").document("Kalibrieren").get().await().toObject<CalibrateRepairPricing>()
emit(Status.success(entity))
}.catch {
Timber.d("Error on getCalibrate Price")
emit(Status.failed(it.message.toString()))
}
// Sends status and object to viewModel
override suspend fun getRepairPrice(): Flow<Status<CalibrateRepairPricing?>> = flow {
emit(Status.loading())
val entity = db.collection("emailprice").document("Kalibrieren").get().await().toObject<CalibrateRepairPricing>()
emit(Status.success(entity))
}.catch {
Timber.d("Error on getRepairPrice")
emit(Status.failed(it.message.toString()))
}
}
ViewModel
private lateinit var calibrateRepairPrice: CalibrateRepairPricing
private val _calirateRepairPriceErrorState = MutableLiveData<Status<Unit>>()
val calibrateRepairPriceErrorState: LiveData<Status<Unit>> get() = _calirateRepairPriceErrorState
init {
viewModelScope.launch {
when(_subject.value.toString()) {
"Toast" -> emailRepository.getCalibratePrice().collect {
when(it) {
is Status.Success -> {
calibrateRepairPrice = it.data!!
_calirateRepairPriceErrorState.postValue(Status.success(Unit))
}
is Status.Loading -> _calirateRepairPriceErrorState.postValue(Status.loading())
is Status.Failure -> _calirateRepairPriceErrorState.postValue(Status.failed(it.message))
}
}
else -> emailRepository.getRepairPrice().collect {
when(it) {
is Status.Success -> {
calibrateRepairPrice = it.data!!
_calirateRepairPriceErrorState.postValue(Status.success(Unit))
}
is Status.Loading -> _calirateRepairPriceErrorState.postValue(Status.loading())
is Status.Failure -> _calirateRepairPriceErrorState.postValue(Status.failed(it.message))
}
}
}
price.postValue(calibrateRepairPrice.head!!.basePrice)
}
}
You can now observe the status in one of your fragments (but you dont need to!)
Fragment
viewModel.calibrateRepairPriceErrorState.observe(viewLifecycleOwner) { status ->
when(status) {
is Status.Success -> requireContext().toast("Price successfully loaded")
is Status.Loading -> requireContext().toast("Price is loading")
is Status.Failure -> requireContext().toast("Error, Price could not be loaded")
}
}
This is my toast extensions function:
fun Context.toast(text: String, duration: Int = Toast.LENGTH_SHORT) {
Toast.makeText(this, text, duration).show()
}

Retrofit call using abstraction with kotlin is not calling onChange

I want to abstract the retrofit call, so I don't need to write the same boiler plate code when I need a request.
The abstraction
open class NetworkCall<T> {
lateinit var call: Call<T>
var result: MutableLiveData<Resource<T>> = MutableLiveData()
fun makeCall(call: Call<T>) {
this.call = call
val callBackKt = CallBackKt<T>()
callBackKt.result.value = Resource.loading(null)
this.call.enqueue(callBackKt)
result = callBackKt.result
}
class CallBackKt<T> : Callback<T> {
var result: MutableLiveData<Resource<T>> = MutableLiveData()
override fun onFailure(call: Call<T>, t: Throwable) {
result.value = Resource.error()//APIError()
t.printStackTrace()
}
override fun onResponse(call: Call<T>, response: Response<T>) {
if (response.isSuccessful) {
result.value = Resource.success(response.body())
}
else {
result.value = Resource.error()
}
}
}
}
Repository
class DetailsRepository(val application: Application) {
private val myListDao =
AppDatabase.getDatabase(application)?.MyListDao()
var movie: MutableLiveData<Resource<DetailsDTO>> = MutableLiveData()
fun getDetails(id: Int) {
val networkCall = NetworkCall<DetailsDTO>()
networkCall.makeCall(Apifactory.tmdbApi.getDetails(id))
movie = networkCall.result
}
}
ViewModel
class DetailsViewModel(application: Application) : AndroidViewModel(application) {
private val repository: DetailsRepository = DetailsRepository(application)
internal var movie: LiveData<Resource<DetailsDTO>> = repository.movie
fun insert(myListItem: MyListItem) {
repository.insert(myListItem)
}
fun fetchDetails(id: Int) {
repository.getDetails(id)
}
}
Activity
viewModel.movie.observe(this, Observer {
it?.apply {
detail_title.text = data?.title
}
})
Log with in every method says it's being called in right order and that the request is working fine. Althoght onChange is not being called.
fetchDetails called
getDetails called
makeCall called
onResponse successful, result.value.data = DetailsDTO(adult=false, backdrop_path=/y8lEIjYZCi2VFP4ixtHSn2klpth.jpg, ...
...
What would be done wrong?