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How to implement a dynamic list view inside fragment android studio in Kotlin

I have two fragments that share information with each other, in the first one I have an edit text and button widget. The second fragment is just a listview. When the user clicks the button, it displays whatever is in the edit text widget in the second fragment.
So if the user enters the text study and clicks the button the second fragment will display
Study
If the user then enters the text eat and clicks the button, the second fragment will display
Study
Eat
I am having so issues with displaying the texts
So far this is what I have done
class FirstFragment : Fragment() {
override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?): View? {
viewModel = activity?.run { ViewModelProvider(this)[MyViewModel::class.java]
} ?: throw Exception("Invalid Activity")
val view = inflater.inflate(R.layout.one_fragment, container, false)
val button = view.findViewById<Button>(R.id.vbutton)
val value = view.findViewById<EditText>(R.id.textView)
button.setOnClickListener {
}
return view;
}
}
class SecondFragment : Fragment() {
lateinit var viewModel: MyViewModel
#SuppressLint("MissingInflatedId")
override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?): View? {
viewModel = activity?.run { ViewModelProvider(this)[MyViewModel::class.java]
} ?: throw Exception("Invalid Activity")
val view = inflater.inflate(R.layout.page3_fragment, container, false)
val valueView = v.findViewById<TextView>(R.id.textView)
return view
The problem I am having is how to display the texts

If I undestand you correctly, you want to share data between fragments? If yes, you can do that with "shared" viewModel. For example:
class FirstFragment : Fragment() {
private var _binding: FragmentFirstBinding? = null
private val binding get() = _binding!!
private val sharedViewModel by activityViewModels<SharedViewModel>()
override fun onCreateView(
inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle?
): View {
_binding = FragmentFirstBinding.inflate(inflater, container, false)
binding.buttonChangeFragment.setOnClickListener {
/*
You can change data here, or in navigateWithNavController() from
activity (You already have an instance of your viewModel in activity)
*/
sharedViewModel.changeData(binding.myEditText.text.toString())
if (requireActivity() is YourActivity)
(requireActivity() as YourActivity).navigateWithNavController()
}
return binding.root
}
}
class SecondFragment : Fragment() {
private var _binding: FragmentSecondBinding? = null
private val binding get() = _binding!!
private val sharedViewModel by activityViewModels<SharedViewModel>()
override fun onCreateView(
inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle?
): View {
_binding = FragmentSecondBinding.inflate(inflater, container, false)
binding.secondFragmentText.text = sharedViewModel.someData.value
return binding.root
}
}
and your activity:
class YourActivity: AppCompatActivity() {
private lateinit var binding: YourActivityBinding
private lateinit var appBarConfiguration: AppBarConfiguration
private val sharedViewModel: SharedViewModel by lazy {
ViewModelProvider(
this
)[SharedViewModel::class.java]
}
private lateinit var navController: NavController
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
binding = YourActivityBinding.inflate(LayoutInflater.from(this))
setContentView(binding.root)
navController = this.findNavController(R.id.nav_host_fragment)
appBarConfiguration = AppBarConfiguration(navController.graph)
}
/*
This function is just for test
*/
fun navigateWithNavController() {
navController.navigate(R.id.secondFragment)
}
override fun onSupportNavigateUp(): Boolean {
return NavigationUI.navigateUp(navController, appBarConfiguration)
}
}
And your viewModel should look something like this:
class SharedViewModel : ViewModel() {
private val _someData = MutableLiveData("")
val someData: LiveData<String>
get() = _someData
fun changeData(newData: String?) {
_someData.value = newData ?: _someData.value
}
}

Your view model should have a backing list of the entered words. When a word is added, the list can be updated, and in turn you can update a LiveData that publishes the latest version of the list.
class MyViewModel: ViewModel() {
private val backingEntryList = mutableListOf<String>()
private val _entryListLiveData = MutableLiveData("")
val entryListLiveData : LiveData<String> get() = _entryListLiveData
fun addEntry(word: String) {
backingEntryList += word
_entryListLiveData.value = backingEntryList.toList() // use toList() to to get a safe copy
}
}
Your way of creating the shared view model is the hard way. The easy way is by using by activityViewModels().
I also suggest using the Fragment constructor that takes a layout argument, and then setting things up in onViewCreated instead of onCreateView. It's less boilerplate code to accomplish the same thing.
In the first fragment, you can add words when the button's clicked:
class FirstFragment : Fragment(R.layout.one_fragment) {
private val viewModel by activityViewModels<MyViewModel>()
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
val button = view.findViewById<Button>(R.id.vbutton)
val value = view.findViewById<EditText>(R.id.textView)
button.setOnClickListener {
viewModel.addEntry(value.text.toString())
}
}
}
In the second fragment, you observe the live data:
class SecondFragment : Fragment(R.layout.page3_fragment) {
private val viewModel by activityViewModels<MyViewModel>()
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
val valueView = view.findViewById<TextView>(R.id.textView)
viewModel.entryListLiveData.observe(viewLifecycleOwner) { entryList ->
valueView.text = entryList.joinToString(" ")
}
}
}

Is it normal for the ViewModel class to be called without setValue on LiveData?

I am studying the MVVM pattern.
I have a question regarding LiveData while using ViewModel class.
Even if I do not change the value of LiveData with setValue or postValue, it continues to observe and execute the fragment.
When addRoutine() is called, vm.observe also continues to run.
As you can see there is no setValue or postValue in addRoutine(), so LiveData has no value change at all.
But why does vm.observe keep running?
This is my code.
ViewModel.kt
class WriteRoutineViewModel : ViewModel() {
private val _items: MutableLiveData<List<RoutineModel>> = MutableLiveData(listOf())
private val rmList = arrayListOf<RoutineModel>()
val items: LiveData<List<RoutineModel>> = _items
fun addRoutine(workout: String) {
val rmItem = RoutineModel(UUID.randomUUID().toString(), workout, "TEST")
rmItem.getSubItemList().add(RoutineDetailModel("2","3","3123"))
rmList.add(rmItem)
// _items.postValue(rmList)
}
fun getListItems() : List<RoutineItem> {
val listItems = arrayListOf<RoutineItem>()
for(testRM in rmList) {
listItems.add(RoutineItem.RoutineModel(testRM.id,testRM.workout,testRM.unit))
val childListItems = testRM.getSubItemList().map { detail ->
RoutineItem.DetailModel("2","23","55")
}
listItems.addAll(childListItems)
}
return listItems
}
}
Fragment
class WriteRoutineFragment : Fragment() {
private var _binding : FragmentWriteRoutineBinding? = null
private val binding get() = _binding!!
private val vm : WriteRoutineViewModel by viewModels { WriteRoutineViewModelFactory() }
private lateinit var epoxyController : RoutineItemController
override fun onCreateView(inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle?): View? {
_binding = FragmentWriteRoutineBinding.inflate(inflater, container, false)
return binding.root
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
getTabPageResult()
// RecyclerView(Epoxy) Update
vm.items.observe(viewLifecycleOwner) { updatedItems ->
epoxyController.setData(vm.getListItems())
}
}
private fun getTabPageResult() {
val navController = findNavController()
navController.currentBackStackEntry?.also { stack ->
stack.savedStateHandle.getLiveData<String>("workout")?.observe(
viewLifecycleOwner, Observer { result ->
vm.addRoutine(result)
stack.savedStateHandle?.remove<String>("workout")
}
)
}
}
}

Fragment not attached to an activity when send data from my frgament to Viewmodel

I have a problem when sending data from my fragment to the ViewModel that says:
java.lang.IllegalStateException fragment not attached to an activity, Shutting down VM , Fatal Exception
val viewmodel :Store1_viewmodel by activityViewModels()
private lateinit var binding: FragmentShakaStoreBinding
lateinit var dataset :MutableList<item1>
lateinit var recycler :RecyclerView
lateinit var tempdataset:MutableList<item1>
lateinit var adapter: shaka_recycler_Adapter
#RequiresApi(Build.VERSION_CODES.O)
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
// Inflate the layout for this fragment
binding = FragmentShakaStoreBinding.inflate(inflater,container,false)
recycler =binding.shakaRecycler
// dataset=viewmodel.get()
dataset= mutableListOf()
val curdate =LocalDate.now().format(DateTimeFormatter.ofPattern("dd-MM-yyyy"))
lifecycleScope.launch {
val db = activity?.let { Store1_Database2.getdatabase(it?.applicationContext) }
db?.itemdao()?.getAll()?.let { dataset.addAll(it) }
adapter =shaka_recycler_Adapter(Shaka_Store(),dataset,Shaka_Store())
onclick(4)
recycler.adapter=adapter
}
recycler.addItemDecoration(DividerItemDecoration(
context,LinearLayoutManager.HORIZONTAL
))
recycler.setHasFixedSize(true)
setHasOptionsMenu(true)
return binding.root
// return inflater.inflate(R.layout.fragment_shaka__store, container, false)
}
override fun onCreateOptionsMenu(menu: Menu, inflater: MenuInflater) {
inflater.inflate(R.menu.add_item,menu)
var menuittem =menu!!.findItem(R.id.search)
val searchview =menuittem.actionView as SearchView
searchview.maxWidth = Int.MAX_VALUE
searchview.setOnQueryTextListener(object :SearchView.OnQueryTextListener{
override fun onQueryTextSubmit(p0: String?): Boolean {
// adapter.filter.filter(p0)
return true
}
override fun onQueryTextChange(p0: String?): Boolean {
adapter!!.filter.filter(p0)
Log.v("worrd",p0.toString())
return true
}
})
super.onCreateOptionsMenu(menu, inflater)
}
override fun onOptionsItemSelected(item: MenuItem): Boolean {
when(item.itemId){
R.id.add_item->{
findNavController().navigate(R.id.action_shaka_Store_to_insert_item)
}
}
return super.onOptionsItemSelected(item)
}
override fun onclick(Name: Int) {
viewmodel.setitemname(Name)
}
}
and this is my viewmodel code
val context = application
private val _clicked = MutableLiveData<Int>()
val clicked :LiveData<Int> = _clicked
fun insert (data :item1){
viewModelScope.launch {
val db =Store1_Database2.getdatabase(context)
db.itemdao().insert_item(data)
Toast.makeText(context,"تم اضافة العنصر بنجاح ",Toast.LENGTH_LONG).show()
}
}
fun setitemname(name:Int){
_clicked.value = name
}
}
I am using a coroutines is this the reason why I can not send data from fragment to viewmodel ?

Dagger hilt injects before data binding

I'm trying to use Dagger hilt in my project. I have an Activity that uses Databinding:
#AndroidEntryPoint
class MainActivity : AppCompatActivity(), SetGreeting {
private lateinit var binding: ActivityMainBinding
#Inject
lateinit var fragmentFactory: FragmentsFactory
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
binding = DataBindingUtil.setContentView(this, R.layout.activity_main)
supportFragmentManager.fragmentFactory = fragmentFactory
...
}
override fun greeting(msg: String) {
binding.greeting.text = msg
}
}
this is how I use greeting interface:
interface SetGreeting {
fun greeting(msg: String)
}
#Module
#InstallIn(ActivityComponent::class)
object SetGreetingModule {
#Provides
fun provideGreeting(): SetGreeting {
return MainActivity()
}
}
which would be used inside of a fragment just like this:
#AndroidEntryPoint
class MainFragment : Fragment() {
private val viewModel: MainViewModel by viewModels()
private lateinit var binding: FragmentMainBinding
#Inject
lateinit var greetings: SetGreeting
override fun onCreateView(
inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle?
): View {
binding = DataBindingUtil.inflate(inflater, R.layout.fragment_main, container, false)
return binding.root
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
viewModel.greeting.observe(viewLifecycleOwner, {
it?.let { msg ->
greetings.greeting(msg)
}
})
}
}
The problem is that when I added Dagger to the project, data binding won't work, and it returns null. So when the override function greeting would be called, I get a null pointer exception.

I think dagger does not call onCreate so
binding = DataBindingUtil.setContentView(this, R.layout.activity_main) is not called then binding will be null.
try to initialize the binding object in init block
init{binding = DataBindingUtil.setContentView(this, R.layout.activity_main) }

Android Room ViewModel initialization in fragment crashes app

The situation is pretty straightforward. I have a simple android app with 4 fragments displayed through a bottom navigation bar, and a central Room database. Each fragment should be able to perform CRUD operations on the DB through a viewmodel (details are probably irrelevant but I'll show this as well to be sure):
class ViewModel(application: Application): AndroidViewModel(application) {
val readAllIngredients: LiveData<List<Ingredient>>
val readAllRecipes: LiveData<List<Recipe>>
private val ingredientRepository: IngredientRepository
private val recipeRepository: RecipeRepository
init {
val ingredientDAO = ShoppingAppDatabase.getDatabase(application).ingredientDAO()
val recipeDAO = ShoppingAppDatabase.getDatabase(application).recipeDAO()
ingredientRepository = IngredientRepository(ingredientDAO)
recipeRepository = RecipeRepository(recipeDAO)
readAllIngredients = ingredientRepository.allIngredients
readAllRecipes = recipeRepository.allRecipes
}
fun addIngredient(ingredient: Ingredient) {
viewModelScope.launch(Dispatchers.IO) {
ingredientRepository.put(ingredient)
}
}
fun deleteIngredient(ingredient: Ingredient) {
viewModelScope.launch(Dispatchers.IO) {
ingredientRepository.delete(ingredient)
}
}
fun addRecipe(recipe: Recipe) {
viewModelScope.launch(Dispatchers.IO) {
recipeRepository.put(recipe)
}
}
fun updateRecipe(recipe: Recipe) {
viewModelScope.launch(Dispatchers.IO) {
recipeRepository.update(recipe)
}
}
fun updateIngredient(ingredient: Ingredient) {
viewModelScope.launch(Dispatchers.IO) {
ingredientRepository.update(ingredient)
}
}
}
I'm initializing a viewmodel in each fragment, but with limited success. Here's a fragment for which everything works fine:
class InventoryFragment() : Fragment() {
private var listAdapter = IngredientAdapter()
private lateinit var viewModel : ViewModel
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_inventory, container, false)
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
listAdapter = IngredientAdapter()
recycler_view.apply {
layoutManager = LinearLayoutManager(activity)
adapter = listAdapter
}
viewModel = ViewModelProvider(this).get(ViewModel::class.java)
viewModel.readAllIngredients.observe(viewLifecycleOwner, Observer { ingredient -> listAdapter.setData(ingredient) })
add_button.setOnClickListener{
val errorMessages = validateInput()
if(errorMessages.isNotEmpty()) {
displayToast(activity, errorMessages)
}
else {
viewModel.addIngredient(Ingredient(
edit_name.text.toString(),
edit_qty.text.toString().toFloat(),
edit_um.text.toString()
))
listAdapter.notifyDataSetChanged()
displayToast(activity, "Ingredient added")
hideKeyboard(activity, requireView().windowToken)
}
clearInput()
}
}
}
I'm initializing it in the onViewCreated callback and yeah, it works fine. Doing the same thing in a different fragment yields.. different results for some reason.
class BrowseFragment() : Fragment() {
private lateinit var viewModel: ViewModel
var recipeAdapter = RecipeAdapter()
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
}
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
return inflater.inflate(R.layout.fragment_browse, container, false)
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
viewModel = ViewModelProvider(this).get(ViewModel::class.java)
viewModel.readAllRecipes.observe(viewLifecycleOwner, Observer { recipe -> recipeAdapter.setData(recipe) })
submit_button.setOnClickListener{
var submitFragment = SubmitFragment(recipeAdapter)
var tr = (view.context as FragmentActivity).supportFragmentManager.beginTransaction()
tr.replace(R.id.fragment_container, submitFragment)
tr.commit()
}
browse_recycler_view.apply {
layoutManager = LinearLayoutManager(activity)
adapter = recipeAdapter
}
}
}
When I try to initialize the viewmodel in onViewCreated, I get an IllegalStateException: Can't access ViewModels from detached fragment exception. Creating it in onCreate doesn't work either, since the lifecycle owner is null, which makes sense I guess. What exactly am I doing wrong here?