I try to learn the MVVM Architecture by implementing a very simple app that takes three inputs from the user and stores them in a Room Database then display the data in a RecyclerView.
From the first try it seems to work well, then the app crashes if one of the inputs is left empty. Now, I want to add some input validations (for now the validations must just check for empty string), but I can't figure it out. I found many answers on stackoverflow and some libraries that validates the inputs, but I couldn't integrate those solutions in my app (most probably it is due to my poor implementation of the MVVM).
This is the code of my ViewModel:
class MetricPointViewModel(private val repo: MetricPointRepo): ViewModel(), Observable {
val points = repo.points
#Bindable
val inputDesignation = MutableLiveData<String>()
#Bindable
val inputX = MutableLiveData<String>()
#Bindable
val inputY = MutableLiveData<String>()
fun addPoint(){
val id = inputDesignation.value!!.trim()
val x = inputX.value!!.trim().toFloat()
val y = inputY.value!!.trim().toFloat()
insert(MetricPoint(id, x , y))
inputDesignation.value = null
inputX.value = null
inputY.value = null
}
private fun insert(point: MetricPoint) = viewModelScope.launch { repo.insert(point) }
fun update(point: MetricPoint) = viewModelScope.launch { repo.update(point) }
fun delete(point: MetricPoint) = viewModelScope.launch { repo.delete(point) }
override fun addOnPropertyChangedCallback(callback: Observable.OnPropertyChangedCallback?) {
}
override fun removeOnPropertyChangedCallback(callback: Observable.OnPropertyChangedCallback?) {
}
}
and this is the fragment where everything happens:
class FragmentList : Fragment() {
// TODO: Rename and change types of parameters
private var param1: String? = null
private var param2: String? = null
//Binding object
private lateinit var binding: FragmentListBinding
//Reference to the ViewModel
private lateinit var metricPointVm: MetricPointViewModel
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
arguments?.let {
param1 = it.getString(ARG_PARAM1)
param2 = it.getString(ARG_PARAM2)
}
}
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
//Setting up the database
val metricPointDao = MetricPointDB.getInstance(container!!.context).metricCoordDao
val repo = MetricPointRepo(metricPointDao)
val factory = MetricPointViewModelFactory(repo)
metricPointVm = ViewModelProvider(this, factory).get(MetricPointViewModel::class.java)
// Inflate the layout for this fragment
binding = FragmentListBinding.inflate(inflater, container, false)
binding.apply {
lifecycleOwner = viewLifecycleOwner
myViewModel = metricPointVm
}
return binding.root
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
initRecyclerview()
}
private fun displayPoints(){
metricPointVm.points.observe(viewLifecycleOwner, Observer {
binding.pointsRecyclerview.adapter = MyRecyclerViewAdapter(it) { selecteItem: MetricPoint -> listItemClicked(selecteItem) }
})
}
private fun initRecyclerview(){
binding.pointsRecyclerview.layoutManager = LinearLayoutManager(context)
displayPoints()
}
private fun listItemClicked(point: MetricPoint){
Toast.makeText(context, "Point: ${point._id}", Toast.LENGTH_SHORT).show()
}
companion object {
/**
* Use this factory method to create a new instance of
* this fragment using the provided parameters.
*
* #param param1 Parameter 1.
* #param param2 Parameter 2.
* #return A new instance of fragment FragmentList.
*/
// TODO: Rename and change types and number of parameters
#JvmStatic
fun newInstance(param1: String, param2: String) =
FragmentList().apply {
arguments = Bundle().apply {
putString(ARG_PARAM1, param1)
putString(ARG_PARAM2, param2)
}
}
}
}
I'm planning also to add a long click to the recyclerview and display a context menu in order to delete items from the database. Any help would be appreciated.
My recycler view adapter implementation:
class MyRecyclerViewAdapter(private val pointsList: List<MetricPoint>,
private val clickListener: (MetricPoint) -> Unit): RecyclerView.Adapter<MyViewHolder>(){
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): MyViewHolder {
val layoutInflater = LayoutInflater.from(parent.context)
val binding: RecyclerviewItemBinding = DataBindingUtil.inflate(layoutInflater, R.layout.recyclerview_item, parent, false)
return MyViewHolder(binding)
}
override fun onBindViewHolder(holder: MyViewHolder, position: Int) {
holder.bind(pointsList[position], clickListener)
}
override fun getItemCount(): Int {
return pointsList.size
}
}
class MyViewHolder(private val binding: RecyclerviewItemBinding): RecyclerView.ViewHolder(binding.root){
fun bind(point: MetricPoint, clickListener: (MetricPoint) -> Unit){
binding.idTv.text = point._id
binding.xTv.text = point.x.toString()
binding.yTv.text = point.y.toString()
binding.listItemLayout.setOnClickListener{
clickListener(point)
}
}
}
Try the following,
fun addPoint(){
val id = inputDesignation.value!!.trim()
if(inputX.value == null)
return
val x = inputX.value!!.trim().toFloat()
if(inputY.value == null)
return
val y = inputY.value!!.trim().toFloat()
insert(MetricPoint(id, x , y))
inputDesignation.value = null
inputX.value = null
inputY.value = null
}
Edit:
you can try the following as well if you wish to let the user know that the value a value is expected
ViewModel
private val _isEmpty = MutableLiveData<Boolean>()
val isEmpty : LiveData<Boolean>
get() = _isEmpty
fun addPoint(){
val id = inputDesignation.value!!.trim()
if(inputX.value == null){
_isEmpty.value = true
return
}
val x = inputX.value!!.trim().toFloat()
if(inputY.value == null){
_isEmpty.value = true
return
}
val y = inputY.value!!.trim().toFloat()
insert(MetricPoint(id, x , y))
inputDesignation.value = null
inputX.value = null
inputY.value = null
}
//since showing a error message is an event and not a state, reset it once its done
fun resetError(){
_isEmpty.value = null
}
Fragment Class
metricPointVm.isEmpty.observe(viewLifecycleOwner){ isEmpty ->
isEmpty?.apply{
if(it){
// make a Toast
metricPointVm.resetError()
}
}
}
Related
We have a random crash on production in this class when accessing the binding at line 10 :
class BulletinFragment : Fragment(R.layout.fragment_bulletins) {
private val bulletinViewModel: BulletinsViewModel by viewModel()
private val binding by viewBinding(FragmentBulletinsBinding::bind)
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
viewLifecycleOwner.lifecycleScope.launch {
viewLifecycleOwner.repeatOnLifecycle(Lifecycle.State.STARTED) {
bulletinViewModel.switchState.collect {
binding.bulletinLiveNotificationsBanner.switch.isSelected = it
}
}
}
}
}
viewModel is provided by Koin, and the binding delegate is Zhuiden's one from here
class FragmentViewBindingDelegate<T : ViewBinding>(
val fragment: Fragment,
val viewBindingFactory: (View) -> T
) : ReadOnlyProperty<Fragment, T> {
private var _binding: T? = null
init {
fragment.lifecycle.addObserver(object : DefaultLifecycleObserver {
override fun onCreate(owner: LifecycleOwner) {
fragment.viewLifecycleOwnerLiveData.observe(fragment) { viewLifecycleOwner ->
viewLifecycleOwner.lifecycle.addObserver(object : DefaultLifecycleObserver {
override fun onDestroy(owner: LifecycleOwner) {
_binding = null
}
})
}
}
})
}
override fun getValue(thisRef: Fragment, property: KProperty<*>): T {
val binding = _binding
if (binding != null) {
return binding
}
val lifecycle = fragment.viewLifecycleOwner.lifecycle
if (!lifecycle.currentState.isAtLeast(Lifecycle.State.INITIALIZED)) {
throw IllegalStateException("Should not attempt to get bindings when Fragment views are destroyed.")
}
return viewBindingFactory(thisRef.requireView()).also { _binding = it }
}
}
fun <T : ViewBinding> Fragment.viewBinding(viewBindingFactory: (View) -> T) =
FragmentViewBindingDelegate(this, viewBindingFactory)
inline fun <T : ViewBinding> AppCompatActivity.viewBinding(
crossinline bindingInflater: (LayoutInflater) -> T
): Lazy<T> {
return lazy(LazyThreadSafetyMode.NONE) {
bindingInflater.invoke(layoutInflater)
}
}
This fragment is called within a viewPager2:
class CartPagerAdapter(fragment: Fragment) : FragmentStateAdapter(
fragment.childFragmentManager,
fragment.viewLifecycleOwner.lifecycle
) {
val firstFragment = FirstFragment()
val secondFragment = SecondFragment()
override fun createFragment(position: Int): Fragment = when (position) {
Tab.FIRST_TAB.tabIndex -> firstFragment
Tab.SECOND_TAB.tabIndex -> secondFragment
Tab.THIRD_TAB.tabIndex -> BulletinFragment()
else -> error("The fragment position should in 0 < x < 2 but was '$position'")
}
fun handleDeeplink(deeplink: Uri) {
when (deeplink.host) {
FIRST_TAB_DEEPLINK_HOST -> firstFragment.handleDeeplink(deeplink)
SECOND_TAB_DEEPLINK_HOST -> secondFragment.handleDeeplink(deeplink)
}
}
override fun getItemCount(): Int = 3
}
class CartHomeFragment : Fragment(R.layout.fragment_cart_home), CartHomeContract.View {
private var tabLayoutMediator: TabLayoutMediator? = null
private val args: CartHomeFragmentArgs by navArgs()
private var initTab: Int? = null
// betSlip needs to scroll to top when displaying QrCodes tab (set when moving to QrCode tab after validating cart)
private val pagerAdapter: CartPagerAdapter by adapter { CartPagerAdapter(this) }
private val binding by viewBinding(FragmentCartHomeBinding::bind)
private val scope
get() = viewLifecycleOwner.lifecycleScope
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
initTab = args.tabIndex
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
initialize()
}
override fun onDestroyView() {
tabLayoutMediator?.detach()
tabLayoutMediator = null
super.onDestroyView()
}
private fun initialize() {
scope.launch {
binding.fragmentCartHomeViewPager.run {
adapter = pagerAdapter
setPagerCurrentItem(this)
offscreenPageLimit = 2
}
tabLayoutMediator = TabLayoutMediator(binding.cartTabLayout, binding.fragmentCartHomeViewPager) { tab, position ->
val (title, contentDesc) = with(getTab(position)) { getString(title) to getString(contentDesc) }
tab.text = title
tab.contentDescription = contentDesc
}
tabLayoutMediator?.attach()
}
}
private fun setPagerCurrentItem(viewPager: ViewPager2) {
val initialIntent = arguments?.getParcelable<Intent>(NavController.KEY_DEEP_LINK_INTENT)
initialIntent?.data?.let {
pagerAdapter.handleDeeplink(it)
viewPager.setCurrentItemForDeeplink(it.host)
initialIntent.data = null
} ?: run {
initTab?.let {
viewPager.setCurrentItem(it, false)
initTab = null
}
}
}
fun getTab(index: Int): Tab {
return Tab.values()[index]
}
private fun ViewPager2.setCurrentItemForDeeplink(deeplink: String?) {
setCurrentItem(Tab.getTabIndexForDeeplink(deeplink), false)
}
companion object {
const val FIRST_TAB_DEEPLINK_HOST = "first"
const val SECOND_TAB_DEEPLINK_HOST = "second"
const val THIRD_TAB_DEEPLINK_HOST = "third"
val DEFAULT_TAB: Tab = Tab.FIRST_TAB
const val SECOND_TAB_DEEPLINK_DETAILS_PATH = "/details"
}
}
enum class Tab(#StringRes val title: Int, #StringRes val contentDesc: Int, val deeplink: String) {
FIRST_TAB(R.string.first_tab_tab_title, R.string.a11y_first_tab, FIRST_TAB_DEEPLINK_HOST),
SECOND_TAB(R.string.second_tab_title, R.string.a11y_second_tab, SECOND_TAB_DEEPLINK_HOST),
THIRD_TAB(R.string.third_tab_title, R.string.a11y_third_tab, THIRD_TAB_DEEPLINK_HOST);
val tabIndex: Int = ordinal
companion object {
fun getTabIndexForDeeplink(deeplink: String?): Int =
(values().firstOrNull { it.deeplink == deeplink }
?: DEFAULT_TAB)
.tabIndex
}
}
In the BulletinFragment, I know that the repeatOnLifecycle block seems useless here but we need it for some reason that is not necessary to explain here. I just would like to understand what is wrong with this piece of code. Actually, we get from crashlytics the following crash happening randomly (rare enough to not succeed to reproduce it, but frequent enough to significantly decrease the crashfree):
Fatal Exception: java.lang.IllegalStateException Can't access the Fragment View's LifecycleOwner when getView() is null i.e., before onCreateView() or after onDestroyView()
androidx.fragment.app.Fragment.getViewLifecycleOwner (Fragment.java:377)
com.mycompany.myapp.common.tools.FragmentViewBindingDelegate.getValue (FragmentViewBindingDelegate.kt:40)
com.mycompany.myapp.feature.cart.home.bulletin.BulletinFragment.<clinit> (BulletinFragment.kt:18)
com.mycompany.myapp.feature.cart.home.bulletin.BulletinFragment.access$getBinding (BulletinFragment.java:15)
com.mycompany.myapp.feature.cart.home.bulletin.BulletinFragment$onViewCreated$2$1$1.emit (BulletinFragment.kt:25)
com.mycompany.myapp.feature.cart.home.bulletin.BulletinFragment$onViewCreated$2$1$1.emit (BulletinFragment.kt:24)
com.mycompany.myapp.domain.usecase.notifications.LiveNotificationsUseCase$getSwitchStateFlow$$inlined$map$1$2.emit (Emitters.kt:227)
com.mycompany.myapp.domain.usecase.notifications.LiveNotificationsUseCase$getSwitchStateFlow$$inlined$map$1$2$1.invokeSuspend (Emitters.kt:12)
kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith (ContinuationImpl.kt:33)
kotlinx.coroutines.internal.DispatchedContinuation.resumeWith (DispatchedContinuation.kt:205)
kotlin.coroutines.SafeContinuation.resumeWith (SafeContinuationJvm.kt:41)
How can we endup with this crash when
we tie the coroutine with the viewLifecycleOwner lifecycleScope
and the collect is done inside a block where the lifecycleOwner state is STARTED, the lifecycleOwner being the view if I properly understand.
How the view can be null in this case ??? Is it related to the ViewPager2
Sorry for the long title, however, I am unsure where this error is at in my code, however, I do suspect the error lies in the implementation of the liveData and Observation.
The app which I am working on is an Unscrambler word app where users have to unscramble the letters displayed on the fragment. My code so far consists of 2 Kotlin classes listed below, a fragment and a ViewModel class.
I have currently assigned the variable _currentScrambledWord as a MutableLiveData<String>() and utilised the backing property in ViewModel.kt
private val _currentScrambledWord = MutableLiveData<String>()
val currentScrambledWord: LiveData<String>
get() = _currentScrambledWord
I then tried to attach an observer to the GameFragment using the code below.
viewModel.currentScrambledWord.observe(viewLifecycleOwner,
{ newWord -> binding.textViewUnscrambledWord.text = newWord
})
From what I understand the LiveData simplifies the process of retrieving data from the ViewModel reducing the amount of code needed.
Here is the error I found in Logcat
Attempt to invoke virtual method 'void androidx.lifecycle.MutableLiveData.setValue(java.lang.Object)' on a null object reference
The error lines in the logcat is as follows
at com.example.android.unscramble.ui.game.GameViewModel.getNextWord(GameViewModel.kt:57)
at com.example.android.unscramble.ui.game.GameViewModel.<init>(GameViewModel.kt:18)
at com.example.android.unscramble.ui.game.GameFragment.getViewModel(GameFragment.kt:39)
at com.example.android.unscramble.ui.game.GameFragment.onViewCreated(GameFragment.kt:76)
Viewmodel.kt
class GameViewModel:ViewModel() {
private var wordsList: MutableList<String> = mutableListOf()
private lateinit var currentWord: String
init {
Log.d("GameFragment", "GameViewModel created!")
getNextWord()
}
private var _score = 0
val score: Int
get() = _score
private var _currentWordCount = 0
val currentWordCount: Int
get() = _currentWordCount
private var _currentScrambledWord = MutableLiveData<String>()
val currentScrambledWord: LiveData<String>
get() = _currentScrambledWord
private fun increaseScore() {
_score += SCORE_INCREASE
}
fun isUserWordCorrect(playerWord: String): Boolean {
if (playerWord.equals(currentWord, true)) {
increaseScore()
return true
}
return false
}
private fun getNextWord() {
currentWord = allWordsList.random()
val tempWord = currentWord.toCharArray()
tempWord.shuffle()
while (String(tempWord).equals(currentWord, false)) {
tempWord.shuffle()
}
if (wordsList.contains(currentWord)) {
getNextWord()
} else {
_currentScrambledWord.value = String(tempWord)
++_currentWordCount
wordsList.add(currentWord)
}
}
fun nextWord(): Boolean {
return if (currentWordCount < MAX_NO_OF_WORDS) {
getNextWord()
true
} else false
}
override fun onCleared() {
super.onCleared()
Log.d("GameFragment", "GameViewModel destroyed!")
}
fun reinitializeData() {
_score = 0
_currentWordCount = 0
wordsList.clear()
getNextWord()
}
}
GameFragment.kt
class GameFragment : Fragment() {
private val viewModel: GameViewModel by viewModels()
// Binding object instance with access to the views in the game_fragment.xml layout
private lateinit var binding: GameFragmentBinding
// Create a ViewModel the first time the fragment is created.
// If the fragment is re-created, it receives the same GameViewModel instance created by the
// first fragment
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View {
binding = GameFragmentBinding.inflate(inflater, container, false)
Log.d("GameFragment1", "GameFragment created/re-created!")
return binding.root
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
Log.d("OnViewCreated", "OnViewCreated working")
// Setup a click listener for the Submit and Skip buttons.
binding.submit.setOnClickListener { onSubmitWord() }
binding.skip.setOnClickListener { onSkipWord() }
// Update the UI
binding.score.text = getString(R.string.score, 0)
binding.wordCount.text = getString(
R.string.word_count, 0, MAX_NO_OF_WORDS)
viewModel.currentScrambledWord.observe(viewLifecycleOwner,
{ newWord -> binding.textViewUnscrambledWord.text = newWord
})
}
/*
* Checks the user's word, and updates the score accordingly.
* Displays the next scrambled word.
*/
private fun onSubmitWord() {
val playerWord = binding.textInputEditText.text.toString()
if (viewModel.isUserWordCorrect(playerWord)) {
setErrorTextField(false)
if (!viewModel.nextWord()) {
showFinalScoreDialog()
}
} else {
setErrorTextField(true)
}
}
/*
* Skips the current word without changing the score.
* Increases the word count.
*/
private fun onSkipWord() {
if (viewModel.nextWord()) {
setErrorTextField(false)
} else {
showFinalScoreDialog()
}
}
/*
* Gets a random word for the list of words and shuffles the letters in it.
*/
private fun getNextScrambledWord(): String {
val tempWord = allWordsList.random().toCharArray()
tempWord.shuffle()
return String(tempWord)
}
/*
* Re-initializes the data in the ViewModel and updates the views with the new data, to
* restart the game.
*/
private fun showFinalScoreDialog() {
MaterialAlertDialogBuilder(requireContext())
.setTitle(getString(R.string.congratulations))
.setMessage(getString(R.string.you_scored, viewModel.score))
.setCancelable(false)
.setNegativeButton(getString(R.string.exit)) { _, _ ->
exitGame()
}
.setPositiveButton(getString(R.string.play_again)) { _, _ ->
restartGame()
}
.show()
}
private fun restartGame() {
viewModel.reinitializeData()
setErrorTextField(false)
}
/*
* Exits the game.
*/
private fun exitGame() {
activity?.finish()
}
/*
* Sets and resets the text field error status.
*/
private fun setErrorTextField(error: Boolean) {
if (error) {
binding.textField.isErrorEnabled = true
binding.textField.error = getString(R.string.try_again)
} else {
binding.textField.isErrorEnabled = false
binding.textInputEditText.text = null
}
}
/*
* Displays the next scrambled word on screen.
*/
override fun onDetach() {
super.onDetach()
Log.d("GameFragment", "GameFragment destroyed!")
}
}
Initialization in Kotlin happens in the order written (top to bottom). Because your init block is listed before you initialize _currentScrambledWord, it is null when you try to use it in init. You should move the init block to the end of the class definition, so it is at least after the LiveData, something like this:
private var wordsList: MutableList<String> = mutableListOf()
private var currentWord: String = "" // doesn't have to be lateinit if you always set it in "init" - better yet, just put a default
private var _score = 0
val score: Int
get() = _score
private var _currentWordCount = 0
val currentWordCount: Int
get() = _currentWordCount
private var _currentScrambledWord = MutableLiveData<String>()
val currentScrambledWord: LiveData<String>
get() = _currentScrambledWord
// other stuff
// init at the very bottom
init {
Log.d("GameFragment", "GameViewModel created!")
getNextWord()
}
Have a look here for some additional context.
I save the users I brought from the database in the room first. And their favorite status in the database is false. Then when I favorite it, I change its status. Every time I do this the adapter reloads. I used DiffUtil for this.
In addition, I expect the status of the adapter to remain the same after favorites on the Detail page, and if favorites are made on the detail page, it should be reflected on the adapter.
Because of the function I called from viewmodel in UserListFragment, all data is reloaded when fragment occurs.
Fragment
#AndroidEntryPoint
class UserListFragment : Fragment() {
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View {
val args: UserListFragmentArgs by navArgs()
val binding = FragmentUserListBinding.inflate(inflater, container, false)
val viewModel = ViewModelProvider(this).get(UserListViewModel::class.java)
(this.activity as AppCompatActivity).supportActionBar?.title = "Github Users"
binding.lifecycleOwner = viewLifecycleOwner
binding.viewModel = viewModel
viewModel.userSearch(args.term) //!!!
binding.userListRecyclerView.adapter = UserListAdapter(UserListAdapter.OnClickListener {
val action = it.login.let { login ->
UserListFragmentDirections.actionUserListFragmentToUserDetailFragment(
login!!
)
}
findNavController().navigate(action)
},viewModel)
viewModel.users.observe(viewLifecycleOwner) {
bindRecyclerView(binding.userListRecyclerView, it)
}
return binding.root
}
}
ViewModel
#HiltViewModel
class UserListViewModel #Inject constructor(
private val repository: RoomRepository,
private val firestoreRepository: FirestoreRepository,
private val githubApiService: GithubApiService,
) :
ViewModel() {
private val _users = MutableLiveData<List<UserEntity>?>()
val users: LiveData<List<UserEntity>?>
get() = _users
private val userEntities: MutableList<UserEntity> = mutableListOf()
private val mutableMap: MutableMap<String?, Any?> = mutableMapOf()
fun userSearch(term: String) {
loadFromCache(term)
viewModelScope.launch {
val getPropertiesDeferred = githubApiService.searchUser(term)
try {
val result = getPropertiesDeferred.body()
result?.users?.forEach {
userEntities.add(
UserEntity(
term = term,
login = it.login,
avatar_url = it.avatar_url,
favorite = "no"
)
)
mutableMap.put(term,userEntities)
}
updateSearchResults(userEntities, term)
firestoreRepository.saveSearchResults(mutableMap,term)
} catch (e: Exception) {
Log.e("userListErr", e.message.toString())
}
}
}
fun favorite(login: String){
viewModelScope.launch {
val list = repository.getUserFavoriteStatus(login)
if (list.isNotEmpty()){
if (list[0].favorite == "no"){
repository.addFavorite(login)
}else{
repository.removeFavorite(login)
}
loadFromCache(list[0].term.toString())
}
}
}
private fun updateSearchResults(userEntities: List<UserEntity>, term: String) {
viewModelScope.launch(Dispatchers.IO) {
val favs = repository.getFavorites(term)
repository.insertSearchResults(userEntities)
if (favs.isNotEmpty()){
favs.forEach {
favorite(it.login.toString())
}
}
loadFromCache(term)
}
}
private fun loadFromCache(term: String) {
viewModelScope.launch() {
val list = repository.getSearchResults(term)
if (list.isNotEmpty()){
_users.value = list
}else{
Log.e("boş","boş dürüm")
}
}
}
}
I m getting data from two End points using flows and assigning those two list to temporary list in ViewModel. For this purpose, I'm using combine function and returning result as stateFlows with stateIn operator but that's not working. Can anyone point me out where I go wrong please.
ViewModel.kt
private val _movieItem: MutableStateFlow<State<List<HomeRecyclerViewItems>>> =
MutableStateFlow(State.Loading())
val movieItems: StateFlow<State<List<HomeRecyclerViewItems>>> = _movieItem
fun getHomeItemList() {
viewModelScope.launch {
val testList: Flow<State<List<HomeRecyclerViewItems.Movie>>> =
settingsRepo.getMovieList().map {
State.fromResource(it)
}
val directorList: Flow<State<List<HomeRecyclerViewItems.Directors>>> =
settingsRepo.getDirectorList().map {
State.fromResource(it)
}
_movieItem.value = combine(testList, directorList) { testList, directorList ->
testList + directorList // This is not working as "+" Unresolve Error
}.stateIn(
viewModelScope,
SharingStarted.WhileSubscribed(5000),
State.loading<Nothing>()
) as State<List<HomeRecyclerViewItems>> // Unchecked cast: StateFlow<Any> to State<List<HomeRecyclerViewItems>>
}
Repository.kt
fun getMovieList(): Flow<ResponseAPI<List<HomeRecyclerViewItems.Movie>>> {
return object :
NetworkBoundRepository<List<HomeRecyclerViewItems.Movie>, List<HomeRecyclerViewItems.Movie>>() {
override suspend fun saveRemoteData(response: List<HomeRecyclerViewItems.Movie>) {
}
override fun fetchFromLocal() {
}
override suspend fun fetchFromRemote(): Response<List<HomeRecyclerViewItems.Movie>> =
apiInterface.getMoviesList()
}.asFlow()
}
fun getDirectorList(): Flow<ResponseAPI<List<HomeRecyclerViewItems.Directors>>> {
return object :
NetworkBoundRepository<List<HomeRecyclerViewItems.Directors>, List<HomeRecyclerViewItems.Directors>>() {
override suspend fun saveRemoteData(response: List<HomeRecyclerViewItems.Directors>) {
}
override fun fetchFromLocal() {
}
override suspend fun fetchFromRemote(): Response<List<HomeRecyclerViewItems.Directors>> =
apiInterface.getDirectorsList()
}.asFlow()
}
Network BoundRepository.kt
#ExperimentalCoroutinesApi
abstract class NetworkBoundRepository<RESULT, REQUEST> {
fun asFlow() = flow<ResponseAPI<REQUEST>> {
val apiResponse = fetchFromRemote()
val remotePosts = apiResponse.body()
if (apiResponse.isSuccessful && remotePosts != null) {
emit(ResponseAPI.Success(remotePosts))
} else {
emit(ResponseAPI.Failed(apiResponse.errorBody()!!.string()))
}
}.catch { e ->
e.printStackTrace()
emit(ResponseAPI.Failed("Server Problem! Please try again Later. "))
}
#WorkerThread
protected abstract suspend fun saveRemoteData(response: REQUEST)
#MainThread
protected abstract fun fetchFromLocal()
#MainThread
protected abstract suspend fun fetchFromRemote(): Response<REQUEST>
}
Endpoints with Sealed Class
#GET("directors")
fun getDirectorsList(): Response<List<HomeRecyclerViewItems.Directors>>
#GET("movies")
fun getMoviesList(): Response<List<HomeRecyclerViewItems.Movie>>
sealed class HomeRecyclerViewItems {
class Title(
val id: Int,
val title: String
) : HomeRecyclerViewItems()
class Movie(
val id: Int,
val title: String,
val thumbnail: String,
val releaseDate: String
) : HomeRecyclerViewItems()
class Directors(
val id: Int,
val name: String,
val avator: String,
val movie_count: Int
) : HomeRecyclerViewItems()
}
Fragment.kt
#AndroidEntryPoint
#ExperimentalCoroutinesApi
class SettingsFragment : BaseBottomTabFragment() {
private var _binding: FragmentSettingsBinding? = null
private val binding get() = _binding!!
private val viewModel by viewModels<SettingViewModel>()
#Inject
lateinit var recyclerViewAdapter: RecyclerViewAdapter
#Inject
lateinit var bundle: Bundle
var finalList = mutableListOf<HomeRecyclerViewItems>()
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
}
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View {
// Inflate the layout for this fragment
_binding = FragmentSettingsBinding.inflate(layoutInflater,container,false)
val view = binding.root
binding.rvMovie.apply {
setHasFixedSize(true)
layoutManager = LinearLayoutManager(activity)
}
bundle.putString("Hello","hihg")
Toast.makeText(activity, "${bundle.getString("Hello")}", Toast.LENGTH_SHORT).show()
finalList.add(HomeRecyclerViewItems.Title(1,"hello"))
return view
}
private fun observeList() {
viewLifecycleOwner.lifecycleScope.launch {
viewLifecycleOwner.lifecycle.repeatOnLifecycle(Lifecycle.State.STARTED){
launch {
viewModel.movieItems.collect { state ->
when(state){
is State.Loading ->{
}
is State.Success->{
if (state.data.isNotEmpty()){
recyclerViewAdapter = RecyclerViewAdapter()
binding.rvMovie.adapter = recyclerViewAdapter
recyclerViewAdapter.submitList(finalList)
}
}
is State.Error -> {
Toast.makeText(activity, "Error", Toast.LENGTH_SHORT).show()
}
else -> Unit
}
}
}
}
}
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
(activity as MainActivity).binding.ivSearch.isGone = true
viewModel.getHomeItemList()
observeList()
}
override fun onDestroyView() {
super.onDestroyView()
_binding = null
}
}
Note: I m following this tutorial simpliedCoding for api data for multirecyclerview but want to implement it with Kotlin State Flow. Any help in this regard is highly appreciated. Thanks.
Your problem is in here
val testList: Flow<State<List<HomeRecyclerViewItems.Movie>>> =
settingsRepo.getMovieList().map {
State.fromResource(it)
}
val directorList: Flow<State<List<HomeRecyclerViewItems.Directors>>> =
settingsRepo.getDirectorList().map {
State.fromResource(it)
}
_movieItem.value = combine(testList, directorList) { testList, directorList ->
testList + directorList
}
They are not returning a List<HomeRecyclerViewItems>, but a State<List<HomeRecyclerViewItems>. Maybe a better name for the variables are testsState and directorsState. After that it will be more clear why you need to unpack the values before combining the lists
_movieItem.value = combine(testsState, directorsState) { testsState, directorsState ->
val homeRecyclerViewItems = mutableListOf<HomeRecyclerViewItems>()
if (testsState is Success) homeRecyclerViewItems.add(testsState.data)
if (directorsState is Success) homeRecyclerViewItems.add(directorsState.data)
homeRecyclerViewItems
}
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