I am using StateFlow in my app and in my Fragment I use this to -
private var job: Job? = null
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
job = lifecycleScope.launchWhenResumed {
viewModel.getData().collect {
// ...
}
}
}
override fun onPause() {
job?.cancel()
super.onPause()
}
As you see I cancel the job in onPause. How could I use a generalized function so that I can avoid doing the job?.cancel in every fragment.
I prefer not to use a BaseFragment
A simple solution would be to utilize the fragments lifecycle to automatically cancel the job when it is paused.
fun CoroutineScope.launchUntilPaused(lifecycleOwner: LifecycleOwner, block: suspend CoroutineScope.() -> Unit){
val job = launch(block = block)
lifecycleOwner.lifecycle.addObserver(object : DefaultLifecycleObserver {
override fun onPause(owner: LifecycleOwner) {
job.cancel()
lifecycleOwner.lifecycle.removeObserver(this)
}
})
}
//Usage
class MyFragment: Fragment() {
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
lifecycleScope.launchUntilPaused(this){
someFlow.collect{
...
}
}
}
}
If you have many of these jobs per fragment, I would advice to use a custom CoroutineScope instead, to avoid having many lifecycle observers active.
class CancelOnPauseScope(lifecycleOwner: LifecycleOwner): CoroutineScope by MainScope(){
init{
lifecycleOwner.lifecycle.addObserver(object : DefaultLifecycleObserver{
override fun onPause(owner: LifecycleOwner) {
cancel()
lifecycleOwner.lifecycle.removeObserver(this)
}
})
}
}
class MyFragment: Fragment() {
private val scope = CancelOnPauseScope(this)
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
scope.launch{
someFlow.collect{
...
}
}
}
}
a new way:
// Start a coroutine in the lifecycle scope
lifecycleScope.launch {
// repeatOnLifecycle launches the block in a new coroutine every time the
// lifecycle is in the STARTED state (or above) and cancels it when it's STOPPED.
repeatOnLifecycle(Lifecycle.State.STARTED) {
}
}
public class AnyOfYourFragments extends AbsractFragment{
//you do here what you want to do
}
And in your AbstractFragment:
public abstract class AbstractFragment extends Fragment{
private var job: Job? = null
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
job = lifecycleScope.launchWhenResumed {
viewModel.getData().collect {
// ...
}
}
}
override fun onPause() {
job?.cancel()
super.onPause()
}
}
I don't know kotlin, so my code is kind of mix with java but i'm sure you got the idea
Related
I use Clean Architecture, LiveData, Navigation component & Bottom Navigation view.
I am creating a simple application with three tabs. By default, the First tab Fragment loads user data using some API. When i go to another tabs and then return to the First tab Fragment, i see, that observe return a new data!
I need observe not to return data again when I switch back to the first tab! what am I doing wrong? Could you help me please?
P.s. For navigation i use sample from navigation-advanced-sample and after switching tabs onDestroy is not called.
First solution in the article Observe LiveData from ViewModel in Fragment said:
One proper solution is to use getViewLifeCycleOwner() as LifeCycleOwer while observing LiveData inside onActivityCreated as follows.
I use following code, but it's not work for me:
override fun onActivityCreated(savedInstanceState: Bundle?) {
super.onActivityCreated(savedInstanceState)
Timber.d("onActivityCreated")
viewModel.getProfileLive().observe(viewLifecycleOwner, observer)
}
Second solution in the article Architecture Components pitfalls — Part 1 recommends using Resetting an existing observer and Manually unsubscribing the observer in onDestroyView(). But it doesn't work for me either...
ProfileFragment.kt
class ProfileFragment : DaggerFragment() {
#Inject
lateinit var viewModel: ProfileFragmentViewModel
private val observer = Observer<Resource<Profile>> {
when (it.status) {
Resource.Status.LOADING -> {
Timber.i("Loading...")
}
Resource.Status.SUCCESS -> {
Timber.i("Success: %s", it.data)
}
Resource.Status.ERROR -> {
Timber.i("Error: %s", it.message)
}
}
};
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
Timber.d("onCreate")
}
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
Timber.d("onCreateView")
return inflater.inflate(R.layout.fragment_profile, container, false)
}
fun <T> LiveData<T>.reObserve(owner: LifecycleOwner, observer: Observer<T>) {
removeObserver(observer)
observe(owner, observer)
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
Timber.d("onViewCreated")
viewModel.getProfileLive().observe(viewLifecycleOwner, observer)
// viewModel.getProfileLive().reObserve(viewLifecycleOwner, observer)
}
override fun onActivityCreated(savedInstanceState: Bundle?) {
super.onActivityCreated(savedInstanceState)
Timber.d("onActivityCreated")
}
override fun onDestroyView() {
super.onDestroyView()
Timber.d("onDestroyView")
// viewModel.getProfileLive().removeObserver(observer)
}
override fun onDestroy() {
super.onDestroy()
Timber.d("onDestroy")
}
override fun onDetach() {
super.onDetach()
Timber.d("onDetach")
}
}
ProfileFragmentViewModel.kt
class ProfileFragmentViewModel #Inject constructor(
private val profileUseCase: ProfileUseCase
) : ViewModel() {
init {
Timber.d("Init profile VM")
}
fun getProfileLive() = profileUseCase.getProfile()
}
ProfileUseCase
class ProfileUseCase #Inject constructor(
private val profileRepository: ProfileRepository
) {
fun getProfile(): LiveData<Resource<Profile>> {
return profileRepository.getProfile()
}
}
ProfileRepository.kt.
class ProfileRepository #Inject constructor(
private val loginUserDao: LoginUserDao,
private val profileDao: ProfileDao,
) {
fun getProfile(): LiveData<Resource<Profile>> =
liveData(Dispatchers.IO)
{
emit(Resource.loading(data = null))
val profile = profileDao.getProfile()
// Emit Success result...
}
}
It's because of how Fragment Lifecycle works. When you move to and fro from a fragment onViewCreated() is called again. In onViewCreated you're calling viewModel.getProfileLive() which returns the livedata upto from the repository and observe to it.
Since onViewCreated() gets called everytime when you move back to the Fragment so is your call to viewModel.getProfileLive() and in turn the repository gets called again which again triggers the observe method in your Fragment.
In order to solve this problem,
create a LiveData variable in your ViewModel, set it to the returned Live Data from Repository.
In the Fragment observe to the LiveData variable of your ViewModel not the one returned from Repository.
That way, your observe method will get triggered on very first time and only when value of your data from repository changes.
In my fragment, I have this code:
fun onViewCreated(view: View, savedInstanceState: Bundle?) {
//...
viewModel.state.observe(viewLifecycleOwner) {
//do something
}
}
And in my ViewModel:
class MyViewModel: ViewModel() {
val state = liveData {
val state = dataSource.getState()
emit(state)
}
}
When I navigate to another fragment or activity, and press back button, Fragment's onCreateView and onViewCreated methods are called, but viewModel.state has the same value. I mean, dataSource.getState() is not called again. I need state to be re-fetched from data source.
Is this possible using liveData builder? If not, how should I do it?
You need just cal load function every time when it needed. One of possible way to do it
ViewModel :
val stateLiveData = MutableLiveData<>()
fun loadData() {
viewModelScope.launch {
val state = dataSource.getState()
stateLiveData.setValue(state)
}
}
Fragment :
fun onViewCreated(view: View, savedInstanceState: Bundle?) {
//...
viewModel.loadData()
viewModel.stateLiveData.observe(viewLifecycleOwner) {
//do something
}
}
I looked for many articles and tried to understand how Live Data is observe changes when MVVM architecture is used.
I have a Fragment A, ViewModel and Repository class.
ViewModel is initiated in onCreateView() method of the fragment.
Api call is initiated just after that in onCreateView() method of fragment.
Data from the Server is observed in onViewCreated method of the fragment.
For the first, it is running perfectly fine. But When I update the user name from another Fragment B and come back to Fragment A.
Api is called again in onResume() method of Fragment A to update UI. But here my Live Data is not observed again and UI is not updated
I didn't understand what I am doing wrong? Why observer is not triggering second time?
Below is the code
class FragmentA : Fragment(){
private lateinit var dealerHomeViewModel: DealerHomeViewModel
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
}
override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
val view = inflater.inflate(R.layout.fragment_home_dealers, container, false)
val dealerHomeFactory = DealerHomeFactory(token!!)
dealerHomeViewModel = ViewModelProvider(this,dealerHomeFactory).get(DealerHomeViewModel::class.java)
dealerHomeViewModel.getDealerHomeData()
return view
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
dealerHomeViewModel.dealerInfoLiveData.observe(viewLifecycleOwner, androidx.lifecycle.Observer {dealerInfo ->
// Update UI
tvDealerName.text = dealerInfo.name
})
}
override fun onResume() {
super.onResume()
dealerHomeViewModel.getDealerHomeData()
}
}
//=========================== VIEW MODEL ===================================//
class DealerHomeViewModel(val token:String) : ViewModel() {
var dealerInfoLiveData:LiveData<DealerInfo>
init {
dealerInfoLiveData = MutableLiveData()
}
fun getDealerHomeData(){
dealerInfoLiveData = DealerHomeRepo().getDealerHomePageInfo(token)
}
}
//======================== REPOSITORY ================================//
class DealerHomeRepo {
fun getDealerHomePageInfo(token:String):LiveData<DealerInfo>{
val responseLiveData:MutableLiveData<DealerInfo> = MutableLiveData()
val apiCall: ApiCall? = RetrofitInstance.getRetrofit()?.create(ApiCall::class.java)
val dealerInfo: Call<DealerInfo>? = apiCall?.getDealerInfo(Constants.BEARER+" "+token,Constants.XML_HTTP)
dealerInfo?.enqueue(object : Callback<DealerInfo>{
override fun onFailure(call: Call<DealerInfo>, t: Throwable) {
Log.d(Constants.TAG,t.toString())
}
override fun onResponse(call: Call<DealerInfo>, response: Response<DealerInfo>) {
if(response.isSuccessful){
when(response.body()?.status){
Constants.SUCCESS -> {
responseLiveData.value = response.body()
}
Constants.FAIL -> {
}
}
}
}
})
return responseLiveData
}
}
I think your problem is that you are generating a NEW mutableLiveData each time you use your getDealerHomePageInfo(token:String method.
First time you call getDealerHomePageInfo(token:String) you generate a MutableLiveData and after on onViewCreated you observe it, it has a value.
In onResume, you call again getDealerHomePageInfo(token:String) that generates a NEW MutableLiveData so your observer is pointing to the OLD one.
What would solve your problem is to pass the reference of your viewModel to your repository so it updates the MutableLiveData with each new value, not generate a new one each time.
Edited Answer:
I would do something like this for ViewModel:
class DealerHomeViewModel(val token:String) : ViewModel() {
private val _dealerInfoLiveData:MutableLiveData<DealerInfo> = MutableLiveData()
val dealerInfoLiveData:LiveData = _dealerInfoLiveData
fun getDealerHomeData(){
DealerHomeRepo().getDealerHomePageInfo(token, _dealerInfoLiveData)
}
}
And this for the DealerHomeRemo
class DealerHomeRepo{
fun getDealerHomePageInfo(token:String, liveData: MutableLiveData<DealerInfo>){
val apiCall: ApiCall? = RetrofitInstance.getRetrofit()?.create(ApiCall::class.java)
val dealerInfo: Call<DealerInfo>? = apiCall?.getDealerInfo(Constants.BEARER+" "+token,Constants.XML_HTTP)
dealerInfo?.enqueue(object : Callback<DealerInfo>{
override fun onFailure(call: Call<DealerInfo>, t: Throwable) {
Log.d(Constants.TAG,t.toString())
}
override fun onResponse(call: Call<DealerInfo>, response: Response<DealerInfo>) {
if(response.isSuccessful){
when(response.body()?.status){
Constants.SUCCESS -> {
liveData.value = response.body()
}
Constants.FAIL -> {
}
}
}
}
})
}
For Observers, use the LiveData as before:
dealerHomeViewModel.dealerInfoLiveData.observe(viewLifecycleOwner, androidx.lifecycle.Observer {dealerInfo ->
// Update UI
tvDealerName.text = dealerInfo.name
})
None of the other instances of this question are solving my problem. I have a Fragment that appears at the end of a transaction sequence. It is meant to close the app when a Timer contained within it completes:
var terminalTimer: Timer? = null
class TerminalFragment : Fragment() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
}
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
// Inflate the layout for this fragment
return inflater.inflate(R.layout.fragment_terminal, container, false)
}
override fun onStart() {
super.onStart()
initUi()
startCountDown()
}
override fun onStop() {
super.onStop()
AppLog.i(TAG, "onStop()")
stopCountDown()
}
private fun startCountDown() {
if (terminalTimer == null) {
terminalTimer = Timer()
terminalTimer!!.schedule(object : TimerTask() {
override fun run() {
AppLog.i(TAG, "Terminal countdown finished")
{
activity?.finish()
}
}, 5000)
}
}
private fun stopCountDown() {
AppLog.i(TAG, "stopCountDown()")
terminalTimer?.cancel()
terminalTimer?.purge()
terminalTimer = null
}
private fun returnToStart() {
AppLog.i(TAG, "returnToStart()")
(context as MainActivity).restartFlow() // calls popBackStackImmediate() for every fragment in the backstack, returning user to the beginning of their flow
}
companion object {
#JvmStatic
fun newInstance(terminalType: String, amountLoaded: Double) =
TerminalFragment().apply {
arguments = Bundle().apply {
}
}
}
}
stopCountDown() is being called whenever the fragment is navigated away from, but it somehow survives sometimes and closes the app from another Fragment. Using logs, I've also discovered that there appears to be 2 instances of this timer sometimes. How do I insure that this countdown is never active outside of this fragment and is cancelled/ destroyed in the Fragment's onStop()?
I have a simple scenario where I do something in fragment and when I receive the LiveData I want to do something in Activity.
ViewModel:
class MyViewModel(application: Application) : AndroidViewModel(application) {
...
fun getUser(id: String): LiveData<User> {
return repository.getUser(id)
}
}
Fragment:
class MyFragment : Fragment() {
private lateinit var myViewModel: MyViewModel
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
activity?.run {
myViewModel = ViewModelProviders.of(this).get(MyViewModel::class.java)
} ?: throw Exception("Invalid Activity")
}
override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
return inflater.inflate(R.layout.fragment, container, false)
}
override fun onActivityCreated(savedInstanceState: Bundle?) {
super.onActivityCreated(savedInstanceState)
button.setOnClickListener {
showProgressBar()
myViewModel.getUser(editText.text.toString()).observe(this, Observer { it ->
//TODO
})
}
}
}
Activity:
class MainActivity : AppCompatActivity() {
private lateinit var myViewModel: MyViewModel
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
myViewModel = ViewModelProviders.of(this).get(MyViewModel::class.java)
//Here I would like to observe the user instance returned from the getUser() method
}
}
So the issue I'm having is that I would like to have an instance of LiveData<User> in MyViewModel so that I could observe it in Activity and Fragment. How can I achieve this?
In Fragemnts (as best practice) Should Use
viewModel.userLiveData.observe(viewLifecycleOwner, Observer {
//your code here
})
In Activity Use
viewModel.userLiveData.observe(this, Observer {
//your code here
})
in class MyViewModel create
val userLiveData =MutableLiveData<User>()
and getter
fun getUserLiveData(id: String): MutableLiveData<User> {
return userLiveData
}
fun getUser(id: String){
val disposableUser = repository.getUser(id)
.subscribe({
userLivedata.postValue(it)
})
}
And in activity or Fragment called
myViewModel.getUserLiveData.observe(this, Observer { it ->
//TODO
})
myViewModel.getUser(...)
And Now in ViewModel you have object User (userLiveData.getValue())
Write method in Activity doSomethingWithUser(user: User)
And in your livedata
myViewModel.getUser(editText.text.toString()).observe(this, Observer { it ->
(requireActivity() as MainActivity).doSomethingWithUser(it)
})