I have this app in which I have a parent fragment, which has 2 child fragments in a ViewPager2 object.
One of the child fragments has an interface to communicate changes on its menu to the parent fragment.
The child fragment in question is TasksListFragment.kt and the parent fragment is TodayFragment.kt
When I try to initialize the interface in the child fragment onAttach() function, I get
FATAL EXCEPTION: main Process: com.rajchenbergstudios.hoygenda, PID:
java.lang.ClassCastException: com.rajchenbergstudios.hoygenda.ui.activity.MainActivity cannot be cast to com.rajchenbergstudios.hoygenda.ui.todaylists.taskslist.TasksListFragment$ChildFragmentListener
I don't understand why I get this error, and it says MainActivity, when the parent is a fragment which is the one implementing the interface in the first place, not the MainActivity.
I have everything set up correctly:
I have an interface in the child fragment
The interface is used on the child fragment onCreateMenu to pass the menu object to its interface function onFragmentMenuChanged(menu: Menu)
I override the child fragment's onAttach() and initialize the interface:
override fun onAttach(context: Context) {
super.onAttach(context)
childFragmentListener = context as ChildFragmentListener
}
I write a function called setListener() which is called from the parent fragment to pass its context this to the function parameter which assigns it to the childFragment listener
fun setListener(listener: ChildFragmentListener) {
this.childFragmentListener = listener
}
The parent fragment implements the child fragment listener as seen in the TodayFragment.kt file
Can you tell me what am I doing wrong or how to implement an interface to effectively communicate from child fragment back to its parent fragment?
TasksListFragment.kt
#ExperimentalCoroutinesApi
#AndroidEntryPoint
class TasksListFragment : Fragment(R.layout.fragment_child_tasks_list), TasksListAdapter.OnItemClickListener {
private val viewModel: TasksListViewModel by viewModels()
private lateinit var searchView: SearchView
private lateinit var childFragmentListener: ChildFragmentListener
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
val binding = FragmentChildTasksListBinding.bind(view)
val tasksListAdapter = TasksListAdapter(this)
binding.apply {
tasksListRecyclerview.layoutTasksListRecyclerview.apply {
adapter = tasksListAdapter
layoutManager = LinearLayoutManager(requireContext())
setHasFixedSize(true)
}
ItemTouchHelper(object: ItemTouchHelper.SimpleCallback(0,
ItemTouchHelper.LEFT or ItemTouchHelper.RIGHT){
override fun onMove(
recyclerView: RecyclerView,
viewHolder: RecyclerView.ViewHolder,
target: RecyclerView.ViewHolder
): Boolean {
return false
}
override fun onSwiped(viewHolder: RecyclerView.ViewHolder, direction: Int) {
val task = tasksListAdapter.currentList[viewHolder.adapterPosition]
viewModel.onTaskSwiped(task)
}
}).attachToRecyclerView(tasksListRecyclerview.layoutTasksListRecyclerview)
}
loadObservable(binding, tasksListAdapter)
loadTasksEventCollector()
loadMenu()
}
private fun loadObservable(binding: FragmentChildTasksListBinding, tasksListAdapter: TasksListAdapter) {
viewModel.tasks.observe(viewLifecycleOwner){ tasksList ->
binding.apply {
HGDAViewStateUtils.apply {
if (tasksList.isEmpty()) {
setViewVisibility(tasksListRecyclerview.layoutTasksListRecyclerview, visibility = View.INVISIBLE)
setViewVisibility(tasksListLayoutNoData.layoutNoDataLinearlayout, visibility = View.VISIBLE)
} else {
setViewVisibility(tasksListRecyclerview.layoutTasksListRecyclerview, visibility = View.VISIBLE)
setViewVisibility(tasksListLayoutNoData.layoutNoDataLinearlayout, visibility = View.INVISIBLE)
tasksListAdapter.submitList(tasksList)
}
}
}
}
}
/**
* TasksListViewModel.TaskEvent.ShowUndoDeleteTaskMessage: Stays in this class. It asks for components relevant to this class.
* TasksListViewModel.TaskEvent.NavigateToEditTaskScreen: Stays in this class. The method it overrides comes from task list adapter.
* TasksListViewModel.TaskEvent.NavigateToDeleteAllCompletedScreen: Stays in this class. Relevant to menu which is in this class.
* TasksListViewModel.TaskEvent.NavigateToDeleteAllScreen: Stays in this class. Relevant to menu which is in this class.
*/
private fun loadTasksEventCollector() {
viewLifecycleOwner.lifecycleScope.launchWhenStarted {
viewModel.tasksEvent.collect { event ->
when (event) {
is TasksListViewModel.TaskEvent.ShowUndoDeleteTaskMessage -> {
Snackbar
.make(requireView(), "Task deleted", Snackbar.LENGTH_LONG)
.setAction("UNDO"){
viewModel.onUndoDeleteClick(event.task)
}
.show()
}
is TasksListViewModel.TaskEvent.NavigateToEditTaskScreen -> {
val action = TodayFragmentDirections
.actionTodayFragmentToTaskAddEditFragment(task = event.task, title = "Edit task", taskinset = null, origin = 1)
findNavController().navigate(action)
}
is TasksListViewModel.TaskEvent.NavigateToAddTaskToSetBottomSheet -> {
val action = TasksListFragmentDirections.actionGlobalSetBottomSheetDialogFragment(task = event.task, origin = 1)
findNavController().navigate(action)
}
is TasksListViewModel.TaskEvent.NavigateToDeleteAllCompletedScreen -> {
val action = TasksListFragmentDirections
.actionGlobalTasksDeleteAllDialogFragment(origin = 1)
findNavController().navigate(action)
}
is TasksListViewModel.TaskEvent.NavigateToDeleteAllScreen -> {
val action = TasksListFragmentDirections
.actionGlobalTasksDeleteAllDialogFragment(origin = 3)
findNavController().navigate(action)
}
}.exhaustive
}
}
}
private fun loadMenu(){
val menuHost: MenuHost = requireActivity()
menuHost.addMenuProvider(object: MenuProvider {
override fun onCreateMenu(menu: Menu, menuInflater: MenuInflater) {
childFragmentListener.onFragmentChanged(menu)
menuInflater.inflate(R.menu.menu_tasks_list_fragment, menu)
val searchItem = menu.findItem(R.id.tasks_list_menu_search)
searchView = searchItem.actionView as SearchView
val pendingQuery = viewModel.searchQuery.value
if (pendingQuery != null && pendingQuery.isNotEmpty()) {
searchItem.expandActionView()
searchView.setQuery(pendingQuery, false)
}
searchView.OnQueryTextChanged{ searchQuery ->
viewModel.searchQuery.value = searchQuery
}
viewLifecycleOwner.lifecycleScope.launchWhenStarted {
menu.findItem(R.id.tasks_list_menu_hide_completed).isChecked =
viewModel.preferencesFlow.first().hideCompleted
}
}
override fun onMenuItemSelected(menuItem: MenuItem): Boolean {
return when (menuItem.itemId) {
R.id.tasks_list_menu_sort_by_date -> {
viewModel.onSortOrderSelected(SortOrder.BY_DATE)
true
}
R.id.tasks_list_menu_sort_by_name -> {
viewModel.onSortOrderSelected(SortOrder.BY_NAME)
true
}
R.id.tasks_list_menu_hide_completed -> {
menuItem.isChecked = !menuItem.isChecked
viewModel.onHideCompletedSelected(menuItem.isChecked)
true
}
R.id.tasks_list_menu_delete_completed -> {
viewModel.onDeleteAllCompletedClick()
true
}
R.id.tasks_list_menu_delete_all -> {
viewModel.onDeleteAllClick()
true
}
else -> false
}
}
}, viewLifecycleOwner, Lifecycle.State.RESUMED)
}
interface ChildFragmentListener {
fun onFragmentChanged(menu: Menu)
}
fun setListener(listener: ChildFragmentListener) {
this.childFragmentListener = listener
}
override fun onItemClick(task: Task) {
viewModel.onTaskSelected(task)
}
override fun onItemLongClick(task: Task) {
viewModel.onTaskLongSelected(task)
}
override fun onCheckboxClick(task: Task, isChecked: Boolean) {
viewModel.onTaskCheckedChanged(task, isChecked)
}
override fun onAttach(context: Context) {
super.onAttach(context)
childFragmentListener = context as ChildFragmentListener
}
override fun onPause() {
super.onPause()
Logger.i(TAG, "onPause", "TasksListFragment paused")
}
override fun onDestroyView() {
super.onDestroyView()
searchView.setOnQueryTextListener(null)
}
}
TodayFragment.kt
#ExperimentalCoroutinesApi
#AndroidEntryPoint
class TodayFragment : Fragment(R.layout.fragment_parent_today), TasksListFragment.ChildFragmentListener {
private val viewModel: TodayViewModel by viewModels()
private lateinit var binding: FragmentParentTodayBinding
private var fabClicked: Boolean = false
private lateinit var tasksListMenu: Menu
private lateinit var viewPager: ViewPager2
private val rotateOpen: Animation by lazy { AnimationUtils.loadAnimation(requireContext(), R.anim.rotate_open_anim) }
private val rotateClose: Animation by lazy { AnimationUtils.loadAnimation(requireContext(), R.anim.rotate_close_anim) }
private val fromBottom: Animation by lazy { AnimationUtils.loadAnimation(requireContext(), R.anim.from_bottom_anim) }
private val toBottom: Animation by lazy { AnimationUtils.loadAnimation(requireContext(), R.anim.to_bottom_anim) }
private val fadeIn: Animation by lazy { AnimationUtils.loadAnimation(requireContext(), R.anim.fade_in) }
private val fadeOut: Animation by lazy { AnimationUtils.loadAnimation(requireContext(), R.anim.fade_out) }
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
binding = FragmentParentTodayBinding.bind(view)
binding.apply {
tasksListTransparentWhiteScreen.setOnClickListener {
fabAnimationsRollBack(binding)
fabClicked = !fabClicked
}
}
setChildFragmentMenus()
initViewPagerWithTabLayout(binding)
todayDateDisplay(binding)
initFabs(binding)
loadTodayEventCollector()
getFragmentResultListeners()
}
private fun setChildFragmentMenus(){
val tasksListFragment = TasksListFragment()
tasksListFragment.setListener(this)
Logger.i(TAG, "setChildFragmentMenus", "TasksListFragment menu set")
}
private fun getFragmentResultListeners() {
setFragmentResultListener("add_edit_request"){_, bundle ->
val result = bundle.getInt("add_edit_result")
onFragmentResult(result)
}
setFragmentResultListener("create_set_request_2"){_, bundle ->
val result = bundle.getInt("create_set_result_2")
onFragmentResult(result)
}
setFragmentResultListener("task_added_to_set_request"){_, bundle ->
val result = bundle.getInt("task_added_to_set_result")
val message = bundle.getString("task_added_to_set_message")
onFragmentResult(result, message)
}
setFragmentResultListener("task_added_from_set_request"){_, bundle ->
val result = bundle.getInt("task_added_from_set_result")
val message = bundle.getString("task_added_from_set_message")
onFragmentResult(result, message)
}
}
private fun onFragmentResult(result: Int, message: String? = ""){
viewModel.onFragmentResult(result, message)
}
/**
* TodayViewModel.TodayEvent.NavigateToAddTaskScreen: Relevant to this class. Belongs to Fab which are all in this class.
* TodayViewModel.TodayEvent.ShowTaskSavedConfirmationMessage: Relevant to this class. Belongs to onFragmentResultListener which is here.
* TodayViewModel.TodayEvent.ShowTaskSavedInNewOrOldSetConfirmationMessage: Relevant to this class. Belongs to onFragmentResultListener which is here.
* TodayViewModel.TodayEvent.ShowTaskAddedFromSetConfirmationMessage: Relevant to this class. Belongs to onFragmentResultListener which is here.
* TodayViewModel.TodayEvent.NavigateToAddTasksFromSetBottomSheet: Relevant to this class. Belongs to Fab which are all in this class.
*/
private fun loadTodayEventCollector() {
viewLifecycleOwner.lifecycleScope.launchWhenStarted {
viewModel.todayEvent.collect { event ->
when (event) {
is TodayViewModel.TodayEvent.NavigateToAddTaskScreen -> {
val action = TodayFragmentDirections
.actionTodayFragmentToTaskAddEditFragment(task = null, title = "Add task"
, taskinset = null, origin = 1)
findNavController().navigate(action)
}
is TodayViewModel.TodayEvent.ShowTaskSavedConfirmationMessage -> {
Snackbar.make(requireView(), event.msg, Snackbar.LENGTH_LONG).show()
setViewPagerPage(0)
}
is TodayViewModel.TodayEvent.ShowTaskSavedInNewOrOldSetConfirmationMessage -> {
Snackbar.make(requireView(), event.msg.toString(), Snackbar.LENGTH_LONG).show()
}
is TodayViewModel.TodayEvent.ShowTaskAddedFromSetConfirmationMessage -> {
Snackbar.make(requireView(), event.msg.toString(), Snackbar.LENGTH_LONG).show()
fabClicked = true
setFabAnimationsAndViewStates(binding)
setViewPagerPage(0)
}
is TodayViewModel.TodayEvent.NavigateToAddTasksFromSetBottomSheet -> {
val action = TasksListFragmentDirections
.actionGlobalSetBottomSheetDialogFragment(task = null, origin = 2)
findNavController().navigate(action)
}
}.exhaustive
}
}
}
// This will soon be used to be 1
private fun setViewPagerPage(index: Int){
viewModel.postActionWithDelay(300, object: TodayViewModel.PostActionListener{
override fun onDelayFinished() {
viewPager.setCurrentItem(index, true)
}
})
}
private fun todayDateDisplay(binding: FragmentParentTodayBinding) {
binding.apply {
tasksListDateheader.apply {
dateHeaderDayofmonth.text = viewModel.getCurrentDayOfMonth()
dateHeaderMonth.text = viewModel.getCurrentMonth()
dateHeaderYear.text = viewModel.getCurrentYear()
dateHeaderDayofweek.text = viewModel.getCurrentDayOfWeek()
}
}
}
private fun initViewPagerWithTabLayout(binding: FragmentParentTodayBinding) {
viewPager = binding.todayViewpager
val tabLayout: TabLayout = binding.todayTablayout
viewPager.adapter = activity?.let { TodayPagerAdapter(it) }
Logger.i(TAG, "initViewPagerWithTabLayout", "viewPager is not null")
TabLayoutMediator(tabLayout, viewPager) { tab, index ->
tab.text = when (index) {
0 -> "Tasks"
1 -> "Journal"
else -> throw Resources.NotFoundException("Tab not found at position")
}.exhaustive
when (index) {
0 -> {
}
1 -> {
fabClicked = false
}
}
}.attach()
}
private fun initFabs(binding: FragmentParentTodayBinding) {
binding.apply {
tasksListFab.setOnClickListener {
onMainFabClick(binding)
}
tasksListSubFab1.setOnClickListener {
Logger.i(TAG, "initFabs", "Coming soon")
}
tasksListSubFab2.setOnClickListener {
viewModel.onAddTasksFromSetClick()
}
tasksListSubFab3.setOnClickListener {
viewModel.onAddNewTaskClick()
}
}
}
private fun onMainFabClick(binding: FragmentParentTodayBinding) {
setFabAnimationsAndViewStates(binding)
}
private fun setFabAnimationsAndViewStates(binding: FragmentParentTodayBinding) {
setFabAnimationVisibilityAndClickability(binding, fabClicked)
fabClicked = !fabClicked
}
private fun setFabAnimationVisibilityAndClickability(binding: FragmentParentTodayBinding, clicked: Boolean) {
if (!clicked) fabAnimationsRollIn(binding) else fabAnimationsRollBack(binding)
}
private fun fabAnimationsRollIn(binding: FragmentParentTodayBinding) {
binding.apply {
HGDAAnimationUtils.apply {
HGDAViewStateUtils.apply {
setViewAnimation(v1 = tasksListFab, a = rotateOpen)
setViewAnimation(v1 = tasksListSubFab1, v2 = tasksListSubFab2, v3 = tasksListSubFab3, a = fromBottom)
setViewAnimation(v1 = tasksListSubFab1Tv, v2 = tasksListSubFab2Tv, v3 = tasksListSubFab3Tv, a = fromBottom)
setViewAnimation(v1 = tasksListTransparentWhiteScreen, a = fadeIn)
setViewVisibility(v1 = tasksListSubFab1, v2 = tasksListSubFab2, v3 = tasksListSubFab3
, v4 = tasksListSubFab1Tv, v5 = tasksListSubFab2Tv, v6 = tasksListSubFab3Tv, visibility = View.VISIBLE)
setViewVisibility(v1 = tasksListTransparentWhiteScreen, visibility = View.VISIBLE)
setViewClickState(v1 = tasksListSubFab1, v2 = tasksListSubFab2, v3 = tasksListSubFab3, clickable = true)
setViewClickState(v1 = tasksListTransparentWhiteScreen, clickable = true)
}
}
}
}
private fun fabAnimationsRollBack(binding: FragmentParentTodayBinding) {
binding.apply {
HGDAAnimationUtils.apply {
HGDAViewStateUtils.apply {
setViewAnimation(v1 = tasksListFab, a = rotateClose)
setViewAnimation(v1 = tasksListSubFab1, v2 = tasksListSubFab2, v3 = tasksListSubFab3, a = toBottom)
setViewAnimation(v1 = tasksListSubFab1Tv, v2 = tasksListSubFab2Tv, v3 = tasksListSubFab3Tv, a = toBottom)
setViewAnimation(v1 = tasksListTransparentWhiteScreen, a = fadeOut)
setViewVisibility(v1 = tasksListSubFab1, v2 = tasksListSubFab2, v3 = tasksListSubFab3
, v4 = tasksListSubFab1Tv, v5 = tasksListSubFab2Tv, v6 = tasksListSubFab3Tv, visibility = View.INVISIBLE)
setViewVisibility(v1 = tasksListTransparentWhiteScreen, visibility = View.INVISIBLE)
setViewClickState(v1 = tasksListSubFab1, v2 = tasksListSubFab2, v3 = tasksListSubFab3, clickable = false)
setViewClickState(v1 = tasksListTransparentWhiteScreen, clickable = false)
}
}
}
}
override fun onFragmentChanged(menu: Menu) {
tasksListMenu = menu
}
override fun onPause() {
super.onPause()
tasksListMenu.clear()
}
}
Fragment is not a Context i.e fragment is not a child of context .
So when you try to cast context as ChildFragmentListener you are actually casting your Activity to ChildFragmentListener which is giving you this RuntimeException . to make it work you can use childFragmentListener = parentFragment as ChildFragmentListener
Also if your Doing this you do not need setListener method anymore.
On other hand i would suggest you do not use listeners to communicate b/w fragments . I see you already using viewModel so just use a shared one to communicate . You can get a shared ViewModel inside child by creating it with parentFragment.
I have the following ViewModel and Fragment -
class HeroesViewModel(private val heroesRepository: HeroesRepository) : ViewModel() {
private val internalUiState = MutableStateFlow<UiState>(UiState.Initial)
val uiState = internalUiState.asLiveData()
private val internalUiAction = MutableSharedFlow<UiAction>(1).apply {
tryEmit(UiAction.GetSuggestedList)
}
val uiAction = internalUiAction.asLiveData()
private val externalUiEvent = MutableSharedFlow<UiEvent>(1)
private val uiEvent = externalUiEvent.asSharedFlow()
init {
observeUiEvents()
}
private fun observeUiEvents() = viewModelScope.launch {
uiEvent.collect { event ->
when (event) {
is UiEvent.ListItemClicked -> {
navigateToHeroDetails(event.heroModel)
}
is UiEvent.SearchTextChanged -> {
getHeroesByName(event.searchText)
}
}
}
}
private fun navigateToHeroDetails(heroModel: HeroesListModel) =
submitAction(UiAction.NavigateToHeroesDetails(heroModel))
private fun getHeroesByName(name: String) = viewModelScope.launch(Dispatchers.IO) {
when (val response = heroesRepository.getHeroesByNameWithSuggestions(name)) {
is NetworkResponse.Success -> {
internalUiState.emit(UiState.Data(response.body as List<HeroesListModel>))
}
is NetworkResponse.Error -> {
response.error.message?.let { message ->
internalUiState.emit(UiState.Error(message))
}
}
else -> {}
}
}
fun getSuggestedHeroesList() = viewModelScope.launch(Dispatchers.IO) {
when (val response = heroesRepository.getSuggestedHeroesList(true)) {
is NetworkResponse.Success -> {
submitState(UiState.Data(response.body as List<HeroesListModel>))
}
is NetworkResponse.Error -> {
response.error.message?.let { message ->
submitState(UiState.Error(message))
}
}
else -> {}
}
}
private fun submitAction(uiAction: UiAction) = internalUiAction.tryEmit(uiAction)
private fun submitState(uiState: UiState) = viewModelScope.launch {
internalUiState.emit(uiState)
}
fun submitEvent(uiEvent: UiEvent) = externalUiEvent.tryEmit(uiEvent)
sealed class UiEvent {
data class SearchTextChanged(val searchText: String) : UiEvent()
data class ListItemClicked(val heroModel: HeroesListModel) : UiEvent()
}
sealed class UiState {
data class Data(val modelsListResponse: List<BaseHeroListModel>) : UiState()
data class Error(val errorMessage: String) : UiState()
object Initial : UiState()
}
sealed class UiAction {
data class NavigateToHeroesDetails(val heroModel: HeroesListModel) : UiAction()
object GetSuggestedList : UiAction()
}
}
class DashboardFragment : Fragment() {
//Class Variables - UI
private lateinit var binding: FragmentDashboardBinding
//Class Variables - Dependency Injection
private val heroesViewModel = get<HeroesViewModel>()
override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View {
binding = FragmentDashboardBinding.inflate(inflater, container, false)
return binding.root
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
init()
observeUiState()
observeUiAction()
}
private fun observeUiAction() = heroesViewModel.uiAction.observe(viewLifecycleOwner) { action ->
when(action){
is HeroesViewModel.UiAction.GetSuggestedList -> {
getSuggestedHeroesList()
}
is HeroesViewModel.UiAction.NavigateToHeroesDetails -> {
navigateToHeroesDetails(action.heroModel)
}
}
}
private fun init() {
binding.heroesSearchView.setOnQueryTextListener(object : OnSearchViewOnlyTextChangedListener() {
override fun onQueryTextChange(newText: String?): Boolean {
if (newText.isNullOrEmpty()) return false
heroesViewModel.submitEvent(HeroesViewModel.UiEvent.SearchTextChanged(newText))
binding.progressBar.setVisiblyAsVisible()
return false
}
})
}
private fun observeUiState() = heroesViewModel.uiState.observe(viewLifecycleOwner) { uiAction ->
when (uiAction) {
is HeroesViewModel.UiState.Data -> {
showHeroesList(uiAction)
}
is HeroesViewModel.UiState.Error -> {
showGeneralError(uiAction)
}
HeroesViewModel.UiState.Initial -> Unit
}
}
private fun navigateToHeroesDetails(heroModel: HeroesListModel) =
findNavController().navigate(DashboardFragmentDirections.actionMainFragmentToHeroesDetailsFragment(heroModel))
private fun showHeroesList(result: HeroesViewModel.UiState.Data) {
binding.heroesList.setContent {
LazyColumn {
items(result.modelsListResponse.toList()) { model ->
if (model is HeroListSeparatorModel)
HeroesListSeparatorItem(model)
else if (model is HeroesListModel)
HeroesListItem(model) {
heroesViewModel.submitEvent(HeroesViewModel.UiEvent.ListItemClicked(model))
}
}
}
}
binding.progressBar.setVisiblyAsGone()
}
private fun showGeneralError(result: HeroesViewModel.UiState.Error) {
Toast.makeText(requireContext(), result.errorMessage, Toast.LENGTH_LONG).show()
binding.progressBar.setVisiblyAsGone()
}
private fun getSuggestedHeroesList() {
heroesViewModel.getSuggestedHeroesList()
binding.progressBar.setVisiblyAsVisible()
}
}
As you can see, I have the replayCache set to 1 in internalUiAction but the value keeps emitting itself. When I navigate using the navigateToHeroesDetails() method and go back using the navigation bar I immediately observe the last uiAction emitted value which is NavigateToHeroesDetails, causing me to navigate again and again to the heroes details screen. This is an endless loop of navigation.
As far as a hint for a solution, if I double tap the navigation 2 times quickly it does indeed go back to the first Fragment. Seems like I am missing something related to SharedFlow
I'm trying to handle fragment clicks in FragmentPagerAdapter, but sometimes I'm getting Fatal Exception: kotlin.UninitializedPropertyAccessException, which says that click listener property is not initialized.
So here is code for the PagerAdapter
class ApplicationListPagerAdapter(
fm: FragmentManager,
private val onListItemClick: (isSent: Boolean, application: Application) -> Unit,
private val onGoToScholarshipsTabClicked: () -> Unit,
private val onGoToPicksTabClicked: () -> Unit
): FragmentPagerAdapter(fm, BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT),
ApplicationListFragment.ClickListener {
override fun getCount(): Int {
return 2
}
override fun getItem(position: Int): Fragment {
val isSent = position == 1
val fragment = ApplicationListFragment.newInstance(isSent)
fragment.setApplicationSelectListener(this)
return fragment
}
override fun getPageTitle(position: Int): CharSequence? {
return if (position == 0) "PICKS" else "SENT"
}
override fun applicationSelected(isSent: Boolean, application: Application) {
onListItemClick(isSent, application)
}
override fun goToScholarshipsTabClicked() {
onGoToScholarshipsTabClicked()
}
override fun goToPicksTabClicked() {
onGoToPicksTabClicked()
}
}
Code how I initialize it in fragment
private lateinit var clickListener: ClickListener
fun setApplicationSelectListener(clickListener: ClickListener) {
this.clickListener = clickListener
}
interface ClickListener {
fun applicationSelected(isSent: Boolean, application: Application)
fun goToScholarshipsTabClicked()
fun goToPicksTabClicked()
}
And here in onClick callback I'm getting crashes sometimes for some users.
private fun initRecyclerView(applications: List<Application>) {
application_list_recyclerView.adapter = ApplicationListItemsAdapter(
context!!,
applications.toMutableList(),
isSent,
this,
applicationViewModel.applicationService,
onClick = {
clickListener.applicationSelected(isSent, it)
},
onDelete = { application: Application, count: Int ->
scholarshipViewModel.unFavoriteScholarship(application.scholarship)
sharedViewModel.deletePickedScholarship(application.scholarship)
applicationSharedViewModel.updatePicksCount(count)
if (count == 0) {
showNoApplicationsFragment()
}
},
onUndoDelete = { application: Application, count: Int ->
sharedViewModel.undoDeletedScholarship(application.scholarship)
applicationSharedViewModel.updatePicksCount(count)
if (count == 1) {
hideNoApplicationsFragment()
}
}
)
application_list_recyclerView.layoutManager = LinearLayoutManager(context!!)
}
Thanks for any advice and I hope my explanation makes senes for everybody
Interface
interface OnItemClickListener {
//just a random method
fun itemClicked(positon: Int)
}
Inside Your Adapter class
private lateinit var listener: OnItemClickListener
fun attachListener(listener: OnItemClickListener){
this.listener = listener
}
Acticity/ Fragment
class MainActivity(): AppCompatActivity(), OnItemClickListener{
// implement interface in case you wanna use methods...
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_chat)
// calling the listener method
myAdapter.attachListener(this)
}
}
above myAdapter is your adapter must be init first which is associate to your adapter class
Here is my activity:
class PlayerDetails : AppCompatActivity(), View.OnClickListener {
...
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_player_details)
val intent = getIntent()
numOfPlayers = intent.getIntExtra("number_of_players", 1)
next_details.setOnClickListener(this)
}
override fun onClick(v: View?) {
for (i in 1..numOfPlayers) {
...
nextUser()
} else {
blankFields()
}
}
}
private fun nextUser() {
}
}
How do I pass the value of i in my for loop to nextUser()?
I tried nextUser(num: Int = i) but it doesn't work.
Any idea?
Change your method to accept a parameter
private fun nextUser(num: Int) { }
And call the function like this
for (i in 1..numOfPlayers) { ... nextUser(i) } else { blankFields() } }
Your nextUser should look like as follow:
private fun nextUser(i: Int = DEFAULT_VALUE) {
}
DEFAULT_VALUE is optional, if you choose you can delete = DEFAULT_VALUE from you function definition. In that case, you always need to pass value when you make a call to nextUser.
Then, from your for loop you can pass i value to nextUser as follow.
for (i in 1..numOfPlayers) {
...
nextUser(i)
} else {
blankFields()
}
The NextUser() function must accept one input param.
Now the Code is like
for(i until numOfPlayers) {
nextuser(i)
}
else {
blankFields()
}
Now the nextUser looks like.
nextUser(value : Int) {
TODO("perform the action")
}
While writing an Android app, I encountered a problem with a stuttering animation. I use AHBottomNavigation for navigation, FragNav is for swapping fragments and FlexibleAdapter for RecyclerView.
The application is built from one activity and five fragments. When I try to switch to the first fragment in the application, the BottomNavigation animation freez for a moment. It looks very unsightly. The second time I choose the same fragment, everything works smoothly. It seems to me that it is the fault to initialize the views in the fragment, but I have no idea how to do it differently.
AHBottomNavigation https://github.com/aurelhubert/ahbottomnavigation
FragNav https://github.com/ncapdevi/FragNav
FlexibleAdapter https://github.com/davideas/FlexibleAdapter
Fragment
class GradeFragment : BaseFragment(), GradeView {
#Inject
lateinit var presenter: GradePresenter
private val gradeAdapter = FlexibleAdapter<AbstractFlexibleItem<*>>(null, null, true)
companion object {
fun newInstance() = GradeFragment()
}
override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
return inflater.inflate(R.layout.fragment_grade, container, false)
}
override fun onActivityCreated(savedInstanceState: Bundle?) {
super.onActivityCreated(savedInstanceState)
presenter.run {
attachView(this#GradeFragment)
loadData()
}
}
override fun initView() {
gradeAdapter.run {
isAutoCollapseOnExpand = true
isAutoScrollOnExpand = true
setOnUpdateListener { presenter.onUpdateDataList(it) }
setOnItemClickListener { position ->
getItem(position).let {
if (it is GradeItem) {
GradeDialog.newInstance(it.grade).show(fragmentManager, it.toString())
}
}
}
}
gradeRecycler.run {
layoutManager = SmoothScrollLinearLayoutManager(context)
adapter = gradeAdapter
}
gradeSwipe.setOnRefreshListener { presenter.loadData(forceRefresh = true) }
}
override fun updateData(data: List<GradeHeader>) {
gradeAdapter.updateDataSet(data, true)
}
override fun isViewEmpty(): Boolean = gradeAdapter.isEmpty
override fun showEmptyView(show: Boolean) {
gradeEmpty.visibility = if (show) VISIBLE else GONE
}
override fun showProgress(show: Boolean) {
gradeProgress.visibility = if (show) VISIBLE else GONE
}
override fun setRefresh(show: Boolean) {
gradeSwipe.isRefreshing = show
}
Presenter
class GradePresenter #Inject constructor(
private val errorHandler: ErrorHandler,
private val schedulers: SchedulersManager,
private val gradeRepository: GradeRepository,
private val sessionRepository: SessionRepository) : BasePresenter<GradeView>(errorHandler) {
override fun attachView(view: GradeView) {
super.attachView(view)
view.initView()
}
fun loadData(forceRefresh: Boolean = false) {
disposable.add(sessionRepository.getSemesters()
.map { it.single { semester -> semester.current } }
.flatMap { gradeRepository.getGrades(it, forceRefresh) }
.map { it.groupBy { grade -> grade.subject } }
.map { createGradeItems(it) }
.subscribeOn(schedulers.backgroundThread())
.observeOn(schedulers.mainThread())
.doFinally { view?.setRefresh(false) }
.doOnSuccess { if (it.isEmpty()) view?.showEmptyView(true) }
.doOnError { view?.run { if (isViewEmpty()) showEmptyView(true) } }
.subscribe({ view?.updateData(it) }) { errorHandler.proceed(it) })
}
private fun createGradeItems(items: Map<String, List<Grade>>): List<GradeHeader> {
return items.map {
val gradesAverage = calcAverage(it.value)
GradeHeader().apply {
subject = it.key
average = view?.run {
if (gradesAverage == 0f) emptyAverageString()
else averageString().format(gradesAverage)
}.orEmpty()
number = view?.gradeNumberString(it.value.size).orEmpty()
subItems = (it.value.map { item ->
GradeItem().apply {
grade = item
weightString = view?.weightString().orEmpty()
valueColor = getValueColor(item.value)
}
})
}
}
}
fun onUpdateDataList(size: Int) {
if (size != 0) view?.showProgress(false)
}
After a few days, I managed to solve the problem by updating the SDK to version 28. RecyclerView no longer causes animation jams when inflating