Develop Reference

call a fragment from another class\function kotlin

GameActivity
____FragmentQuest
____FragmentFight
class MapLvl.kt
this is a text RPG Fragment Quest displays a journey through different maps (changing the content in one fragment according to a template) text, pictures, navigation buttons. if there is a mob on the map, then the "Fight" button appears and a fragment of the turn-based fight FightFragment opens (hit the head \ legs\ body protect the head \ legs\ body). after the battle, return to QuestFragment
class MapLvl fills with the content of FightFragment
I need to change QuestFragment from classLvl to FightFragment. how to do it?
it doesn't work:
class MapLvl.kt:
class MapLevels(){
fun changeLvl (bind: FragmentQuestBinding,hero: Hero, activity: GameActivity,db: Maindb) {
when (hero.mapLvl) {
1 -> MapLevels().mapLevel1(bind, activity, hero, db)
2 -> MapLevels().mapLevel2(bind, activity, hero,db)
else -> {}
}
}
fun mapLevel2 (bind: FragmentQuestBinding,activity: GameActivity,hero:Hero,db: Maindb) {
bind.btnAtack.visibility= View.VISIBLE
//the problem is here:
bind.btnAtack.setOnClickListener {
(activity as GameActivity).supportFragmentManager
.beginTransaction()
.replace(R.id.placeHolder,FightFragment.newInstance())
.commit()
}
}
}
error: FragmentManager has not been attached to a host
QuestFragment:
class QuestFragment : Fragment() {
lateinit var bind:FragmentQuestBinding
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?,
): View {
bind = FragmentQuestBinding.inflate(inflater)
return bind.root
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
val hero = Hero()
val db = Maindb.heroSetDb(requireActivity())
hero.extractHeroData(db,hero)
scopeMain.launch {
delay(50)
MapLevels().changeLvl(bind,hero,GameActivity(),db)
}
if you make a call directly from a Fragment, then it works: (but it is necessary not from the fragment but from the class)
QuestFragment:
class QuestFragment : Fragment() {
lateinit var bind:FragmentQuestBinding
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?,
): View {
bind = FragmentQuestBinding.inflate(inflater)
return bind.root
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
val hero = Hero()
val db = Maindb.heroSetDb(requireActivity())
hero.extractHeroData(db,hero)
scopeMain.launch {
delay(50)
MapLevels().changeLvl(bind,hero,GameActivity(),db)
}
bind.btnAtack.setOnClickListener {
(activity as GameActivity).supportFragmentManager
.beginTransaction()
.replace(R.id.placeHolder,FightFragment.newInstance())
.commit()
}
it Work:
class MapLevels(val bind: FragmentQuestBinding,
val hero: Hero,
val db: Maindb,
val activity: FragmentActivity ){
fun changeLvl() {
when (hero.mapLvl) {
1 -> MapLevels(bind,hero,db,activity).mapLevel1()
2 -> MapLevels(bind,hero,db,activity).mapLevel2()
else -> {}
}
}
fun mapLevel2() {
bind.imgLocation.setImageResource(R.drawable.map_loc02)
bind.txtLocationDiscription.text ="text"
bind.btnAtack.visibility= View.VISIBLE
bind.btnAtack.setOnClickListener {
(activity as FragmentActivity).supportFragmentManager
.beginTransaction()
.replace(R.id.placeHolder,FightFragment.newInstance())
.commit()

MapLevels().changeLvl(bind,hero,GameActivity(),db)
It looks like you are creating a new GameActivity instance to pass to your changeLvl() method. YOU SHOULD NEVER DO THIS. The new activity is NOT the same one that currently is displayed on the screen. Instead, you should use the requireAcitivty() to get the fragment's parent activity:
MapLevels().changeLvl(bind,hero,requireActivity(),db)
I can't be sure this will fix your current problem because I'm not even sure what the problem is exactly. But it is one issue that you need to change.

Fragments UI's overlapping

I'm creating a shopping app where the user can choose next product from the fragment. That will open the next fragment of the same class with more products and so on. I want to use swipe to dismiss behaviour, so when I swipe my finger down I dissmiss the current fragment. It's essential that while swiping the current fragment the user will be able to see the fragment underneath, so I can only use add instead of replace. Here's the problem: When I use add in my fragment manager, the created fragments UI's overlap, which makes the user swipe multiple fragments at once and not show swiping animation. The fragment uses one xml layout so it shares id across all fragments so I have no way of controlling which layouts are disabled. How do I make the user only swipe one fragment/disable touching fragments underneath? The swipe to dissmis is working well with replace but that's not the point. Here's my code.
Activity:
class PullDismissActivity : AppCompatActivity(), PullDismissLayout.Listener {
private lateinit var viewModel: StackingFragmentsViewModel
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_pulldismiss)
viewModel = ViewModelProvider(this).get(StackingFragmentsViewModel::class.java)
supportFragmentManager.beginTransaction()
.add(R.id.pull, SwipeFragment(), null)
.addToBackStack(null) // name can be null
.commit()
val layout = findViewById<PullDismissLayout>(R.id.pull)
layout.setListener(this)
}
override fun onDismissed() {
viewModel.popBackStack()
supportFragmentManager.popBackStack()
}
override fun onShouldInterceptTouchEvent(): Boolean {
return false
}
Fragment:
class SwipeFragment : Fragment() {
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
val viewModel = ViewModelProvider(requireActivity()).get(StackingFragmentsViewModel::class.java)
viewModel.addFragment(this.hashCode())
val fragid = view.findViewById<TextView>(R.id.fragid)
fragid?.text = System.currentTimeMillis().toString()
val button = view.findViewById<Button>(R.id.button)
button.setOnClickListener {
requireActivity().supportFragmentManager.beginTransaction()
.add(R.id.pull, SwipeFragment(), null)
.addToBackStack(null)
.commit()
}
}
override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
return inflater.inflate(R.layout.fragment,container,false)
}

backstack with navigation component

using the navigation component on two fragments, my app currently destroys a fragment when navigateUp() is called (using the setupActionBarWithNavController()), and therefore when I enter the deleted fragment, all progress is lost, I am trying to change that my adding the fragment to a backstack (and only one instance of the fragment) but I've been struggling with that...
Here's some code:
MainActivity:
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
loginRepository = LoginRepository()
if (!loginRepository.checkLoggedInState()) {
goToLoginActivity()
}
Log.d("FirebaseMain", "onCreate: ${loginRepository.checkLoggedInState()}")
//MyApplication.app.currentUser
binding = DataBindingUtil.setContentView(this, R.layout.activity_main)
navController = Navigation.findNavController(this, R.id.nav_host_fragment)
// setup custom action bar
setSupportActionBar(findViewById(R.id.toolbar))
// adds a return button in the ActionBar.
NavigationUI.setupActionBarWithNavController(this, navController)
}
FormFragment:
(the fragment I want to save its progress and add to backstack)
class FormFragment : Fragment() {
private lateinit var binding: FragmentFormBinding
private val checkListRecyclerAdapter = CheckListRecyclerAdapter(
hashMapOf(
0 to "mirrors",
1 to "blinkers1",
2 to "blinkers11",
3 to "blin4kers",
4 to "blink3e1123rs",
5 to "blink6ers",
6 to "blin53kers",
7 to "blin8kers",
8 to "blin7kers",
9 to "blin43kers",
10 to "blin32kers",
11 to "blin322kers",
)
)
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
}
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
binding = DataBindingUtil.inflate(inflater, R.layout.fragment_form, container, false)
binding.rvCheckList.apply {
// this is used to load the data sequentially from top to bottom,
this.layoutManager = LinearLayoutManager(context)
// the adapter that loads the data into the list
this.adapter = checkListRecyclerAdapter
}
return binding.root
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
}
}
Thanks in advance for any help!

I've been struggling with some similar to this.
Fragments in Navigation Component doesnt keep their state. If you keep your data progress while navigate, you need create a SharedViewModel scoped to a Navigation Graph.
In Fragment:
private val navGraphScopedViewModel by navGraphViewModels<NavGraphViewModel>(R.id.your_nav_graph)
Create this class:
class NavGraphViewModel : ViewModel() {
var sharedData= CustomObject()
}
And from all your fragments you can access and set data:
val data = navGraphScopedViewModel.sharedData
I hope I've helped you

Shared element does not return to RecyclerView item

I have a fragment called MainFragment that contains a ViewPager that contains another fragment called LibraryFragment.
LibraryFragment contains a RecyclerView with a list of items that contain an ImageView. The ImageView's contents are loaded with Coil.
When an item is clicked, LibraryFragment navigates to another fragment called ArtistDetailFragment and uses the ImageView from the item.
The problem is that while the enter transition works fine, the ImageView does not return to the list item when navigating back and only fades away. Ive attached an example below:
Ive tried using postponeEnterTransition() and startPostponedEnterTransition() along with adding a SharedElementCallback but neither have worked that well. I've also ruled out Coil being the issue.
Heres LibraryFragment:
class LibraryFragment : Fragment() {
private val musicModel: MusicViewModel by activityViewModels()
private val libraryModel: LibraryViewModel by activityViewModels()
private lateinit var binding: FragmentLibraryBinding
override fun onCreateView(
inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
binding = FragmentLibraryBinding.inflate(inflater)
binding.libraryRecycler.adapter = ArtistAdapter(
musicModel.artists.value!!,
BindingClickListener { artist, itemBinding ->
navToArtist(artist, itemBinding)
}
)
return binding.root
}
private fun navToArtist(artist: Artist, itemBinding: ItemArtistBinding) {
// When navigation, pass the artistImage of the item as a shared element to create
// the image popup.
findNavController().navigate(
MainFragmentDirections.actionShowArtist(artist.id),
FragmentNavigatorExtras(
itemBinding.artistImage to itemBinding.artistImage.transitionName
)
)
}
}
Heres ArtistDetailFragment:
class ArtistDetailFragment : Fragment() {
override fun onCreateView(
inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
val binding = FragmentArtistDetailBinding.inflate(inflater)
sharedElementEnterTransition = TransitionInflater.from(requireContext())
.inflateTransition(android.R.transition.move)
val musicModel: MusicViewModel by activityViewModels()
val artistId = ArtistDetailFragmentArgs.fromBundle(requireArguments()).artistId
// Get the transition name used by the recyclerview ite
binding.artistImage.transitionName = artistId.toString()
binding.artist = musicModel.artists.value?.find { it.id == artistId }
return binding.root
}
}
And heres the RecyclerView Adapter/ViewHolder:
class ArtistAdapter(
private val data: List<Artist>,
private val listener: BindingClickListener<Artist, ItemArtistBinding>
) : RecyclerView.Adapter<ArtistAdapter.ViewHolder>() {
override fun getItemCount(): Int = data.size
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
return ViewHolder(
ItemArtistBinding.inflate(LayoutInflater.from(parent.context))
)
}
override fun onBindViewHolder(holder: ViewHolder, position: Int) {
holder.bind(data[position])
}
// Generic ViewHolder for an artist
inner class ViewHolder(
private val binding: ItemArtistBinding
) : RecyclerView.ViewHolder(binding.root) {
// Bind the view w/new data
fun bind(artist: Artist) {
binding.artist = artist
binding.root.setOnClickListener { listener.onClick(artist, binding) }
// Update the transition name with the new artist's ID.
binding.artistImage.transitionName = artist.id.toString()
binding.executePendingBindings()
}
}
}
EDIT: I used postponeEnterTransition and startPostponedEnterTransition like this:
// LibraryFragment
override fun onResume() {
super.onResume()
postponeEnterTransition()
// Refresh the parent adapter to make the image reappear
binding.libraryRecycler.adapter = artistAdapter
// Do the Pre-Draw listener
binding.libraryRecycler.viewTreeObserver.addOnPreDrawListener {
startPostponedEnterTransition()
true
}
}
This only makes the RecyclerView itself refresh however, the shared element still fades away instead of returning to the RecyclerView item.

Chris Banes says;
You may wonder why we set the OnPreDrawListener on the parent rather than the view itself. Well that is because your view may not actually be drawn, therefore the listener would never fire and the transaction would sit there postponed forever. To work around that we set the listener on the parent instead, which will (probably) be drawn.
https://chris.banes.dev/fragmented-transitions/
try this;
change
// LibraryFragment
override fun onResume() {
super.onResume()
postponeEnterTransition()
// Refresh the parent adapter to make the image reappear
binding.libraryRecycler.adapter = artistAdapter
// Do the Pre-Draw listener
binding.libraryRecycler.viewTreeObserver.addOnPreDrawListener {
startPostponedEnterTransition()
true
}
}
enter code here
to
override fun onCreateView(
inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
postponeEnterTransition()
binding = FragmentLibraryBinding.inflate(inflater)
binding.libraryRecycler.adapter = ArtistAdapter(
musicModel.artists.value!!,
BindingClickListener { artist, itemBinding ->
navToArtist(artist, itemBinding)
}
)
(view?.parent as? ViewGroup)?.doOnPreDraw {
// Parent has been drawn. Start transitioning!
startPostponedEnterTransition()
}
return binding.root
}

ViewPager not loading Pages after the first time I navigate to the ViewPager

I have a Fragment that contains a ViewPager. When I navigate to this fragment I see the first page as expected. However, if I hit back, and then navigate to that fragment again, I am then presented with a blank white screen...
What I'm noticing in the Layout Inspector is that when I navigate to the ViewPager Fragment the second time, the ViewPager is present, but none of the page fragments are in the hierarchy.
Here is how I set up my viewPager in my ViewPagerFragment:
/**
* Variables
*/
var pageOneFragment = ForgotPasswordInitiateFragment()
var pageTwoFragment = ForgotPasswordSubmitCodeFragment()
var pageThreeFragment = ForgotPasswordSubmitPasswordFragment()
lateinit var mViewPager: ForgotPasswordViewPager
lateinit var mPagerAdapter: ForgotPasswordPagerAdapter
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
}
override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
return inflater.inflate(R.layout.forgot_password_pager_fragment, container, false)
}
override fun onActivityCreated(savedInstanceState: Bundle?) {
super.onActivityCreated(savedInstanceState)
forgotPasswordViewModel = ViewModelProviders.of(this, viewModelFactory)
.get(ForgotPasswordViewModel::class.java)
pageOneFragment.viewPager = this
pageTwoFragment.viewPager = this
pageThreeFragment.viewPager = this
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
activity?.let {
mPagerAdapter = ForgotPasswordPagerAdapter(it.supportFragmentManager)
}
mViewPager = viewPager
mViewPager.adapter = mPagerAdapter
mViewPager.setListeners()
}
override fun onResume() {
super.onResume()
}
inner class ForgotPasswordPagerAdapter(fm: FragmentManager): FragmentPagerAdapter(fm) {
override fun getItem(position: Int): Fragment {
when (position) {
0 -> return pageOneFragment
1 -> return pageTwoFragment
2 -> return pageThreeFragment
else -> throw IllegalStateException("Pager position $position is out of bounds.")
}
}
override fun getCount(): Int {
return 3
}
}
I attempted to set all my mViewPager configurations into the onResume function but the same thing happened.
When does the viewPager actually populate its pages? Because what it seems like to me is they are populated the first time, but not the second....
EDIT:
I debugged the Activity's fragments on the back pressed and noticed that the pages were in that fragment stack, but not the actual viewPager fragment.

You're using
activity?.let {
mPagerAdapter = ForgotPasswordPagerAdapter(it.supportFragmentManager)
}
I.e., using the activity's FragmentManager. That's always the wrong thing to do and the source of your issue. Instead, you need to use the Fragment's childFragmentManager:
mPagerAdapter = ForgotPasswordPagerAdapter(childFragmentManager)