I have a SearchFragment with the following code.
#AndroidEntryPoint
class SearchFragment :
Fragment(),
View.OnClickListener {
...
private var _binding: FragSearchBinding? = null
private val binding get() = _binding as FragSearchBinding
private val viewmodel by viewModels<SearchViewModel>()
override fun onCreateView(
inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle?
)
: View {
_binding = FragSearchBinding.inflate(inflater, container, false)
binding.fragSearchSearchResultFilter.setOnClickListener(this)
return binding.root
}
...
private fun showFilterDialog() {
val dialog = FilterBottomSheetDialogFragment.newInstance()
dialog.show(parentFragmentManager, "filter_bsd_tag")
}
...
}
I am showing a FilterBottomSheetDialogFragment using that SearchFragment. I want to pass the ViewModel of SearchFragment to the DialogFragment. I have this code for my FilterBottomSheetDialogFragment.
#AndroidEntryPoint
class FilterBottomSheetDialogFragment :
BottomSheetDialogFragment(),
View.OnClickListener {
companion object {
fun newInstance() = FilterBottomSheetDialogFragment()
private const val TAG_SELECTION_DIALOG = "tag_selection_dialog"
}
private var _binding: BsdFilterBinding? = null
private val binding get() = _binding as BsdFilterBinding
private val viewmodel: SearchViewModel = ???
}
I have tried
private val viewmodel by viewModels<SearchViewModel>(ownerProducer = { this.requireParentFragment() })
The above doesn't work as it just creates a new instance of ViewModel.
I also tried
private val viewmodel: SearchViewModel by lazy {
ViewModelProvider(requireParentFragment()).get(SearchViewModel::class.java)
}
The above doesn't work with the error saying that the SearchViewModel instance cannot be created. My SearchViewModel has this constructor.
#HiltViewModel
class SearchViewModel #Inject constructor(
private val courseRepository: CourseRepository
) : ViewModel()
How can I pass the SearchViewModel to the DialogFragment without using the constructor parameter?
You're mistake here is actually the fragment manager you're using when showing your dialog. Currently you're using the parent fragment manager, whereas your dialog should exist as a child fragment of the fragment it is being shown from.
So you should be using:
dialog.show(childFragmentManager, "filter_bsd_tag")
which will then ensure that
viewModels<SearchViewModel>(ownerProducer = { requireParentFragment() })
refers to the SearchFragment.
Related
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 am making a simple application. There are 2 screens in the application: List screen, Add screen.
Scenario: When the application is opened, there is a list page on the screen. The user goes to the Adding page with the help of the Floating Action Button on the list page. Here, he enters the items with the help of Edit Text and comes to the List page by pressing the Add Button.
I am using MVVM in this application and I am a beginner. So I can't find the problem. Here is the problem: I am adding new elements to my list in the Add Fragment, but these elements are not seems in the List Fragment.
Thanks in advance.
Model Class
data class Movie(
val movieName: String,
val releaseDate: String
)
ViewModel class
class MovieViewModel : ViewModel() {
val movies = MutableLiveData<ArrayList<Movie>>()
var movieList = arrayListOf<Movie>()
fun addMovie(movie: Movie) {
movieList.add(movie)
movies.value = movieList
}
}
Adapter Class
class MovieAdapter : RecyclerView.Adapter<MovieAdapter.MyViewHolder>() {
private var movieList = emptyList<Movie>()
class MyViewHolder(private val binding: RowItemBinding) :
RecyclerView.ViewHolder(binding.root) {
fun bind(movie: Movie) {
binding.textViewMovieName.text = movie.movieName
binding.textViewReleaseDate.text = movie.releaseDate
}
}
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): MyViewHolder {
val layoutInflater = LayoutInflater.from(parent.context)
val binding = RowItemBinding.inflate(layoutInflater, parent, false)
return MyViewHolder(binding)
}
override fun onBindViewHolder(holder: MyViewHolder, position: Int) {
val currentItem = movieList[position]
holder.bind(currentItem)
}
override fun getItemCount(): Int {
return movieList.size
}
fun setData(movie: List<Movie>) {
val movieDiffUtil = MovieDiffUtil(movieList, movie)
val movieDiffResult = DiffUtil.calculateDiff(movieDiffUtil)
this.movieList = movie
movieDiffResult.dispatchUpdatesTo(this)
}
}
Add Fragment
class AddFragment : Fragment() {
private var _binding: FragmentAddBinding? = null
private val binding get() = _binding!!
private val movieViewModel: MovieViewModel by viewModels<MovieViewModel>()
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
_binding = FragmentAddBinding.inflate(inflater, container, false)
binding.buttonAdd.setOnClickListener {
insertData()
}
return binding.root
}
private fun insertData() {
val movieName = binding.editTextMovieName.text.toString()
val releaseDate = binding.editTextReleaseDate.text.toString()
val movie = Movie(movieName, releaseDate)
movieViewModel.addMovie(movie)
findNavController().navigate(R.id.action_addFragment_to_listFragment)
}
override fun onDestroyView() {
super.onDestroyView()
_binding = null
}
}
List Fragment
class ListFragment : Fragment() {
private var _binding: FragmentListBinding? = null
private val binding get() = _binding!!
private val adapter: MovieAdapter by lazy { MovieAdapter() }
private val movieViewModel: MovieViewModel by viewModels<MovieViewModel>()
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
_binding = FragmentListBinding.inflate(inflater, container, false)
setAdapter()
movieViewModel.movies.observe(viewLifecycleOwner, { data ->
adapter.setData(data)
binding.textView.setText(data.get(0).movieName)
})
binding.floatingActionButton.setOnClickListener {
findNavController().navigate(R.id.action_listFragment_to_addFragment)
}
return binding.root
}
private fun setAdapter() {
val recyclerView = binding.recyclerView
recyclerView.adapter = adapter
recyclerView.layoutManager = LinearLayoutManager(requireActivity())
}
override fun onDestroyView() {
super.onDestroyView()
_binding = null
}
}
After adding an item to a List<> you need to notify the Adapter that the data has changed.
You can do so by calling adapter.notifyDataSetChanged().
I added my List directly into the Adapter but you can create a function like in the following stackoverflow post.
How to update my Recyclerview using kotlin android?
I have a method onBind() that I want to use with a scope of binding, is there a way to achieve this?
Currently, I have a variable (“binding: T”) and an abstract function onBind() in BaseBindableFragment, and in my implementation I use with(binding){} to scope onBind(). I want to avoid using with(binding) and make it so that in implementation I get onBind() { this: T -> }
My abstract class
abstract class BaseBindableFragment<T : ViewDataBinding> : Fragment() {
protected lateinit var binding: T
private set
protected abstract val layout: Int
#LayoutRes get
override fun onCreateView(
inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
binding = DataBindingUtil.inflate(inflater, layout, container, false)
// Wrap with(binding){onBind()} in a way that `onBind` executes with `binding` as `this`
onBind()
return binding.root
}
protected abstract fun onBind()
}
And then in my implementation
override fun onBind() = with(binding) { // <- I want to avoid this "= with(binding)" line
lifecycleOwner = viewLifecycleOwner
viewModel = myViewModel
}
protected abstract fun T.onBind()
and
binding = DataBindingUtil.inflate(inflater, layout, container, false)
binding.onBind()
return binding.root
The implementation becomes
override protected fun T.onBind() {
lifecycleOwner = viewLifecycleOwner
viewModel = myViewModel
}
(or e.g. MyBinding.onBind() if your class extends BaseBindableFragment<MyBinding>)
I'm using recyclerView to display my data but anything is displaying. The onBindViewHolder is never called and the onCreateViewHolder also.
I initialize the adapter in the viewModel with the data which I got from room but anything is displaying. The data in the viewModel is there when I want give it to the adaptater.
There's the adaptater,
class CountryInfoAdapter : RecyclerView.Adapter<TextItemViewHolder>() {
var data = listOf<DevByteCountryProperty>()
set(value) {
field = value
notifyDataSetChanged()
}
override fun getItemCount() = data.size
override fun onBindViewHolder(holder: TextItemViewHolder, position: Int) {
val item = data[position]
holder.textView.text = item.name.toString()
}
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): TextItemViewHolder {
//The inflater knows how to create views from XML layout. The context is the context of the RecyclerView.
val layoutInflater = LayoutInflater.from(parent.context)
val view = layoutInflater.inflate(R.layout.text_item_view, parent, false) as TextView
Timber.i("Data from adaptater : ${data.toString()}")
return TextItemViewHolder(view)
}
}
There is the Fragment,
class CountryInfoFragment : Fragment() {
private lateinit var viewModel: CountryInfoViewModel
private lateinit var viewModelFactory: CountryInfoViewModelFactory
private lateinit var binding: FragmentCountryInfoBinding
override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?): View? {
binding = DataBindingUtil.inflate(inflater,
R.layout.fragment_country_info,container,false)
val application = requireNotNull(this.activity).application
viewModelFactory = CountryInfoViewModelFactory(application)
viewModel = ViewModelProvider(this,viewModelFactory).get(CountryInfoViewModel::class.java)
binding.viewModel = viewModel
val adapter = CountryInfoAdapter()
viewModel.countriesProperty.observe(viewLifecycleOwner, Observer {
it?.let {
adapter.data = it
}
})
binding.countryList.adapter = adapter
binding.lifecycleOwner = viewLifecycleOwner
setHasOptionsMenu(true)
return binding.root
}
}
Please try below code, setting up layout manager before assigning adapter to recyclerView
binding.countryList.layoutManager = LinearLayoutManager(this)
binding.countryList.adapter = adapter