I'm trying to add more fragments dynamically inside my ViewPager2 however when I call the adapter.add(MyNewFragment, position) 2 things happens, if I use notifyDataSetChange() is not showing up the fragment but if I put notifyItemInserted(position) is showing up but the app crashes with an java.lang.IllegalStateException: Fragment already added.
This is my adapter class:
class ViewPagerAdapter(
list: MutableList<Fragment>,
fm: FragmentManager,
lifecycle: Lifecycle,
//fragmentActivity: FragmentActivity
) : FragmentStateAdapter(fm, lifecycle) {
var fragmentList = list
override fun getItemCount(): Int {
return fragmentList.size
}
fun addScreen(fragment: Fragment, position: Int) {
if(!fragmentList.contains(fragment)){
fragmentList.add(position, fragment)
//notifyItemInserted(position)
notifyDataSetChanged()
}
}
override fun createFragment(position: Int): Fragment {
return fragmentList[position]
}
// I tried to use these methods that I saw here but then the viewpager is totally blank and does not load anything or do the same Fragment already added error.
/* override fun getItemId(position: Int): Long {
return fragmentList[position].id.toLong()
}
override fun containsItem(itemId: Long): Boolean = fragmentList.any { it.id.toLong() == itemId }*/
}
And this is my the screen where the viewPager is:
#AndroidEntryPoint
class ViewPagerScreen : Fragment() {
//...
override fun onCreateView(
inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle?
): View {
if (!::savedViewInstance.isInitialized) {
_binding = FragmentViewPagerScreenBinding.inflate(inflater, container, false)
//....
savedViewInstance = binding.root
}
binding.viewPager.isSaveEnabled = false
return savedViewInstance
}
fun addNewScreen(){
adapter.addScreen(NewFragment(), binding.viewPager.currentItem + 1)
}
private fun initViewPager() {
binding.viewPager.offscreenPageLimit = 2
binding.viewPager.registerOnPageChangeCallback(object : ViewPager2.OnPageChangeCallback() {
override fun onPageScrolled(
position: Int,
positionOffset: Float,
positionOffsetPixels: Int
) {
super.onPageScrolled(position, positionOffset, positionOffsetPixels)
}
})
adapter = ViewPagerAdapterByFragments(
mutableListOf(FirstScreen(), SecondScreen(), ThirdScreen()),
this#ViewPagerScreen.childFragmentManager,
lifecycle
)
binding.viewPager.adapter = adapter
binding.viewPager.isUserInputEnabled = false
}
}
I think I solved the problem, thanks #snachmsm for pointing me out where to look for.
What I did was quite simple, I only had to change the param list: MutableList<Fragment> to list:MutableList<Pair<String,Fragment>> where my String is my fragmentId. Then on the method createFragment return a new fragment base on my fragmentId.
Here's the code itself:
override fun createFragment(position: Int): Fragment {
return when (fragmentList!![position]!!.first) {
"firstScreen" -> return FirstScreen()
"secondScreen" ->return SecondScreen()
"thirdScreen" ->return ThirdScreen()
"newScreen" -> return NewScreen()
else -> AnotherScreen()
}
}
Also my addScreenMethod() now looks like this:
fun addScreen(newfragment: Pair<String, Fragment>, position: Int) {
val result = fragmentList.find {
it.first == newfragment.first
}
if (result == null) {
fragmentList.add(position, newfragment)
notifyItemInserted(position)
}
}
Related
I am getting exception:
E/MessageQueue-JNI: java.lang.IllegalArgumentException: No view found for id 0x7f0a0554 (ua.com.company.app:id/vpBanners) for fragment BannerItemFragment{30698be} (4c80b228-4303-4c80-b99d-a55b8359b8c2) id=0x7f0a0554}
My hierarchy looks like so:
My adapter for vpHome:
class HomeViewPagerAdapter(fm: FragmentManager) : FragmentStatePagerAdapter(fm, BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT) {
private val mFragmentList: MutableList<Fragment> = ArrayList()
private val mFragmentTitleList: MutableList<String> = ArrayList()
override fun getItem(position: Int): Fragment {
return mFragmentList[position]
}
override fun getCount(): Int {
return mFragmentList.size
}
override fun getPageTitle(position: Int): CharSequence? {
return mFragmentTitleList[position]
}
fun addFragment(fragment: Fragment, title: String) {
mFragmentList.add(fragment)
mFragmentTitleList.add(title)
}
}
And I apply it in this way:
private fun setupViewPager(viewPager: DisableSwipeViewPager) {
vpAdapter = HomeViewPagerAdapter(childFragmentManager).apply {
addFragment(ForYouFragment(), "for you")
addFragment(AnotherFragment1(), "a1")
addFragment(AnotherFragment2(), "a2")
}
viewPager.adapter = vpAdapter
}
Next, my SnapBannersCarouselViewHolder to handle items with ViewPager inside:
class SnapBannersCarouselViewHolder(
private val mBinding: HomeFragmentItemSnapBannersCarouselBinding
) : RecyclerView.ViewHolder(mBinding.root) {
companion object {
// ...
fun newInstance(
inflater: LayoutInflater,
parent: ViewGroup,
onMoreInteractionListener: ((infoBlockId: String) -> Unit)?
): SnapBannersCarouselViewHolder {
val binding =
HomeFragmentItemSnapBannersCarouselBinding.inflate(inflater, parent, false)
return SnapBannersCarouselViewHolder(
binding,
onMoreInteractionListener
)
}
}
fun bind(item: SnapBannersItem, fragmentManager: FragmentManager) {
// ...
val adapter = BannerPagesAdapter(fragmentManager, item.banners)
with(mBinding.vpBanners) {
// ...
this.adapter = adapter
offscreenPageLimit = 3
}
}
}
My RecyclerView adapter ForYouContentAdapter:
class ForYouContentAdapter(
var data: List<HomeBaseItem> = emptyList(),
var fragmentManagerRetriever: () -> FragmentManager
) : BaseRecyclerViewAdapter<HomeBaseItem>(data) {
enum class ViewType(val value: Int) {
// ...
SNAP_BANNERS(6)
}
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): RecyclerView.ViewHolder {
return when (viewType) {
// ...
ViewType.SNAP_BANNERS.value -> SnapBannersCarouselViewHolder.newInstance(
mInflater!!,
parent,
onBannersMoreInteractionListener // todo possibly change it
)
else -> throw RuntimeException("Can not create view holder for undefined view type")
}
}
override fun onBindViewHolder(holder: RecyclerView.ViewHolder, position: Int) {
when (getItemViewType(position)) {
// ...
ViewType.SNAP_BANNERS.value -> {
val vHolder = holder as SnapBannersCarouselViewHolder
vHolder.bind(
getItem(position) as SnapBannersItem,
fragmentManagerRetriever.invoke()
)
}
}
}
}
And my fragmentManagerRetriever implementation in ForYouFragment looks like so:
private val fragmentManagerRetriever: () -> FragmentManager = {
childFragmentManager
}
My BannerItemFragment code:
class BannerItemFragment : Fragment() {
private lateinit var mBinding: HomeFragmentSnapBannerItemBinding
companion object {
// ...
fun newInstance(
item: RectWebViewItem
): BannerItemFragment {
return BannerItemFragment()
}
}
override fun onCreateView(
inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
mBinding = HomeFragmentSnapBannerItemBinding.inflate(inflater, container, false)
return mBinding.root
}
// ...
}
In every place where I need to create fragments inside other fragments I am using childFragmentManager.
And when I open ForYouFragment first time, it works normally. My item with ViewPager works normally. But when I replace fragment in Activity's container (adding to back stack) being on ForYouFragment and then return back (back on HomeFragment because ForYouFragment inside HomeFragment), I am getting error.
To replace fragments I am using this method inside ForYouFragment:
private fun showAnotherFragment() {
ActivityUtils.replaceFragmentToActivity(
requireActivity(),
SomeFragment.newInstance(),
true
)
}
And ActivityUtils code:
object ActivityUtils {
fun replaceFragmentToActivity(
activity: FragmentActivity,
fragment: Fragment,
addToBackStack: Boolean
) {
replaceFragmentToActivity(activity, fragment, addToBackStack, containerId = R.id.fragmentContainer)
}
fun replaceFragmentToActivity(
activity: FragmentActivity,
fragment: Fragment,
addToBackStack: Boolean,
containerId: Int
) {
val fragmentManager = activity.supportFragmentManager
val transaction = fragmentManager.beginTransaction()
transaction.replace(containerId, fragment)
if (addToBackStack) {
transaction.addToBackStack(null)
}
transaction.commitAllowingStateLoss()
}
}
Please, help me understand why I am getting this exception?
UPD
Adapter for ViewPager inside RecyclerView:
class BannerPagesAdapter(
fragmentManager: FragmentManager,
var data: List<RectWebViewItem>
) : FragmentStatePagerAdapter(
fragmentManager,
BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT
) {
private var fragments: MutableList<BannerItemFragment> = mutableListOf()
init {
// initial empty fragments
for (i in data.indices) {
fragments.add(BannerItemFragment())
}
}
override fun getItem(position: Int): Fragment {
return BannerItemFragment.newInstance(data[position])
}
override fun getCount(): Int {
return fragments.size
}
override fun instantiateItem(container: ViewGroup, position: Int): Any {
val f = super.instantiateItem(container, position)
fragments[position] = f as BannerItemFragment
return f
}
}
Solved
The problem was that fragments want to be attached to the ViewPager before the ViewPager is attached to its parent. This question outlined here.
So, to solve this problem, I created custom ViewPager:
/**
* Use this ViewPager when you need to place ViewPager inside RecyclerView.
* [LazyViewPager] allows you to set [PagerAdapter] in lazy way. This prevents IllegalStateException
* in case when the fragments want to be attached to the viewpager before the viewpager is
* attached to its parent
*/
class LazyViewPager
#JvmOverloads
constructor(
context: Context,
attrs: AttributeSet? = null
) : ViewPager(context, attrs) {
private var mPagerAdapter: PagerAdapter? = null
override fun onAttachedToWindow() {
super.onAttachedToWindow()
if (mPagerAdapter != null) {
super.setAdapter(mPagerAdapter)
}
}
override fun onDetachedFromWindow() {
super.onDetachedFromWindow()
super.setAdapter(null)
}
#Deprecated("Do not use this method to set adapter. Use setAdapterLazy() instead.")
override fun setAdapter(adapter: PagerAdapter?) {}
fun setAdapterLazy(adapter: PagerAdapter?) {
mPagerAdapter = adapter
}
}
And then, instead of using setAdapter() I use setAdapterLazy().
Also, it is important to reset adapter to null in onDetachedFromWindow().
Ok, I got the following fragment with callback there witch I'm setting to ViewPager2 adapter:
class PremiumFragment : BaseFragment(), OnPageChanged {
override fun getLogTag(): String {
return TAG
}
private lateinit var pagerCounter: ImageView
private lateinit var viewPager: ViewPager2
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
viewPager = view.findViewById(R.id.view_pager) as ViewPager2
viewPager.adapter = ViewPagerAdapter(this)
pagerCounter = view.findViewById(R.id.counter)
}
companion object {
const val TAG = "PremiumFragment"
fun getInstance(): BaseFragment {
Log.d(TAG, "getInstance()")
val args = Bundle()
args.putInt(ARG_LAYOUT_ID, R.layout.premium_f)
val fragment =
PremiumFragment()
fragment.arguments = args
return fragment
}
}
override fun onPageChanged() {
when (viewPager.currentItem) {
0 -> pagerCounter.setImageResource(R.drawable.circle_1)
1 -> pagerCounter.setImageResource(R.drawable.circle_2)
2 -> pagerCounter.setImageResource(R.drawable.circle_3)
}
}
}
My adapter:
class ViewPagerAdapter constructor(val callback: OnPageChanged) : RecyclerView.Adapter<PagerVH>() {
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): PagerVH =
PagerVH(LayoutInflater.from(parent.context).inflate(R.layout.viewpager_f, parent, false))
override fun getItemCount(): Int = Images.values().size
override fun onBindViewHolder(holder: PagerVH, position: Int) = holder.itemView.run {
pager_container.findViewById<ImageView>(R.id.imageView)
.setImageResource(Images.values()[position].image)
}
override fun getItemViewType(position: Int): Int {
callback.onPageChanged()
return super.getItemViewType(position)
}
companion object {
enum class Images(private val value: Int, val image: Int) {
First(0, R.drawable.wow_girl),
Second(1, R.drawable.insights_girl_2),
Third(2, R.drawable.remind_girl);
}
}
}
It should set new drawable every time we swipe ViewPager, but it changes image in fragment only once an then it is not working, have completely no idea where in adapter I should call my callback for a proper behavior, please tell me where should I call this callback? Appreciate any advices!
So I found out that you should call callback from onViewDetachedFromWindow for it calls every time you swipe fragment, and it is quite logical
override fun onViewDetachedFromWindow(holder: PagerVH) {
callback.onPageChanged()
super.onViewDetachedFromWindow(holder)
}
in my scenario i have viewpager inside fragment A and viewpage havefragment C and Fragment D. now i move to fragment B and get back to fragment A and get this crash
java.lang.IllegalStateException: The specified child already has a parent. You must call removeView() on the child's parent first.
adapter=ViewPagerAdapter(childFragmentManager)
class ViewPagerAdapter internal constructor(fm: FragmentManager) : FragmentStatePagerAdapter(fm,BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT) {
private val COUNT = 3
override fun getItem(position: Int): Fragment {
var fragment: Fragment? = null
when (position) {
0 -> fragment = AdditionInfo()
1 -> fragment = UploadFiles()
2 -> fragment = UploadDocs()
}
return fragment!!
}
override fun getCount(): Int {
return COUNT
}
override fun getPageTitle(position: Int): CharSequence? {
return "Tab " + (position + 1)
}
override fun getItemPosition(`object`: Any): Int {
return POSITION_NONE
}
}
fun viewpagerListener() {
viewOfLayout!!.upload_info_doc_viewpager?.setAllowedSwipeDirection(SwipeDirection.left)
viewOfLayout!!.upload_info_doc_viewpager?.offscreenPageLimit = 3
viewOfLayout!!.upload_info_doc_viewpager?.setSaveFromParentEnabled(true)
viewOfLayout!!.upload_info_doc_viewpager?.addOnPageChangeListener(object : ViewPager.OnPageChangeListener {
override fun onPageScrollStateChanged(state: Int) {
}
override fun onPageScrolled(position: Int, positionOffset: Float, positionOffsetPixels: Int) {
currentPage = position
}
override fun onPageSelected(position: Int) {
}
})
}
When i get back to Fragment A i do this
override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?): View? {
if(viewOfLayout==null){
// my code
viewOfLayout = inflater.inflate(R.layout.layout_file, container, false)
adapter=ViewPagerAdapter(childFragmentManager)
}
return viewOfLayout
}
when onCreateView method called and viewOfLayout is already in memory but its called viewpager fragments automatically.```
Just keep the fragment A when it not being shown.
mViewPager.setOffscreenPageLimit(number);
number variable is the number of fragments in viewpager.
i have an issue with an app that use ViewPager for display fragment. All works fine until the app goes in background and be killed from OS. It seems that after restore i have 2 IncidentScreenFragment that handle events, one with a null presenter (MVP) that crash my app.
My HomeActivity looks like:
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
presenter.onViewCreated()
initViews(savedInstanceState)
}
private fun initViews(savedInstanceState: Bundle?){
mapView.onCreate(savedInstanceState)
mapView.getMapAsync(this)
initFragment()
initMenu()
}
private fun initFragment(){
homeFragment = HomeScreenFragment.newInstance()
incidentFragment = IncidentScreenFragment.newInstance()
chatFragment = ChatFragment.newInstance()
weatherFragment = WeatherFragment.newInstance()
viewPager.adapter = ViewPagerAdapter(supportFragmentManager, this)
viewPager.offscreenPageLimit = 4
viewPager?.addOnPageChangeListener(object : ViewPager.OnPageChangeListener {
override fun onPageScrollStateChanged(state: Int) {}
override fun onPageScrolled(position: Int, positionOffset: Float, positionOffsetPixels: Int) {}
override fun onPageSelected(position: Int) {bottom_navigation.currentItem = position}
})
}
override fun getFragmentByPos(pos: Int): Fragment {
return when(pos){
0 -> homeFragment
1 -> incidentFragment
2 -> chatFragment
3 -> weatherFragment
else -> {
homeFragment
}
}
}
And my Adapter:
class ViewPagerAdapter internal constructor(fm: FragmentManager, activity:infinite_software.intelligence_center.intelligencecenter.ui.home.FragmentManager) : FragmentPagerAdapter(fm) {
private val COUNT = 4
private val activity = activity
override fun getItem(position: Int): Fragment{
var fragment: Fragment? = null
when (position) {
0 -> fragment = activity.getFragmentByPos(0)
1 -> fragment = activity.getFragmentByPos(1)
2 -> fragment = activity.getFragmentByPos(2)
3 -> fragment = activity.getFragmentByPos(3)
}
return fragment!!
}
override fun destroyItem(container: ViewGroup, position: Int, `object`: Any) {
super.destroyItem(container, position, `object`)
}
override fun getCount(): Int {
return COUNT
}
override fun getPageTitle(position: Int): CharSequence? {
return "Section " + (position + 1)
}
}
Each Fragment have a static method that return new Fragment:
companion object {
fun newInstance(): HomeScreenFragment {
return HomeScreenFragment()
}
}
When the app has been killed in background i figure out that there is 2 objects (Fragment) that listen to event, one with Presenter correctly instantiate and one without.
Below my abstract BaseFragment class:
abstract class BaseFragment<P : BasePresenter<BaseView>> : BaseView,Fragment() {
protected lateinit var presenter: P
override fun getContext(): Context {
return activity as Context
}
override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
return super.onCreateView(inflater, container, savedInstanceState)
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
presenter = instantiatePresenter()
}
override fun showError(error: String) {
(activity as BaseActivity<BasePresenter<BaseView>>).showError(error)
}
override fun showError(errorResId: Int) {
(activity as BaseActivity<BasePresenter<BaseView>>).showError(errorResId)
}
abstract fun onBackPressed(): Boolean
/**
* Instantiates the presenter the Fragment is based on.
*/
protected abstract fun instantiatePresenter(): P
abstract val TAG: String
Incident Fragment code:
class IncidentScreenFragment: BaseFragment<IncidentScreenPresenter>(), BaseView, IncidentView, AlertFilterListener, AlertItemClickListener, IncidentDetailListener {
var rvAdapter : IncidentAdapter? = null
var state : Int = LIST_STATE
override fun instantiatePresenter(): IncidentScreenPresenter {
return IncidentScreenPresenter(this)
}
override val TAG: String
get() = "INCIDENT"
override fun getContext(): Context {
return activity as Context
}
override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
super.onCreateView(inflater, container, savedInstanceState)
return inflater.inflate(R.layout.fragment_incident, container, false)
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
initViews()
presenter.onViewCreated()
initObserve()
}
private fun initViews(){
//Reclycler view
alertRV.layoutManager = LinearLayoutManager(context)
rvAdapter = IncidentAdapter(ArrayList(), context, this)
alertRV.adapter = rvAdapter
//Apply Listeners
headerBox.setFilterListener(this)
incidentDetailView.setListener(this)
}
override fun initObserve() {
//Init observe presenter model
val alertObserver = Observer<ArrayList<AlertModel>> { alerts ->
Timber.d("Data received from Presenter [$alerts]")
showAlertList(alerts)
}
presenter.filteredAlertList.observe(context as BaseActivity<BasePresenter<BaseView>>,alertObserver)
}
override fun updateThisFilters(boxState: Boolean, level: Int) {
presenter.updateFilterList(boxState,level)
}
fun showOnlyThisLevel(level:Int){
presenter.showOnlyThisLevel(level)
headerBox.disableBoxExcept(level)
}
fun showAlertList(list: ArrayList<AlertModel>){
rvAdapter?.updateData(list)
}
override fun onItemClick(model: AlertModel) {
presenter.loadAlertDetail(model)
}
override fun showAlertDetail(model: AlertModel) {
incidentDetailView.setUpFromModel(model)
WhiteWizard.slideLeftEffect(incidentDetailView,incidentListRootElement)
state = DETAIL_STATE
}
override fun onbackFromDetailPressed() {
WhiteWizard.slideRightEffect(incidentListRootElement,incidentDetailView)
state = LIST_STATE
}
override fun showLoader() {
loaderIncident.visibility = View.VISIBLE
}
override fun hideLoader() {
loaderIncident.visibility = View.INVISIBLE
}
override fun onBackPressed(): Boolean {
when(state){
LIST_STATE -> return false
DETAIL_STATE -> {
onbackFromDetailPressed()
return true
}
else -> return false
}
}
fun newInstance(): IncidentScreenFragment {
return IncidentScreenFragment()
}
}
When i click on the button in homePage to display fragment content i got:
Process: XXXXXX, PID: 3192
kotlin.UninitializedPropertyAccessException: lateinit property presenter has not been initialized
at infinite_software.intelligence_center.intelligencecenter.base.BaseFragment.getPresenter(BaseFragment.kt:11)
at XXXXXX.ui.home.incidentScreen.IncidentScreenFragment.showOnlyThisLevel(IncidentScreenFragment.kt:78)
at XXXXXX.ui.home.HomeActivity.filterDataWithSeverity(HomeActivity.kt:110)
at XXXXXX.ui.home.homeScreen.HomeScreenFragment.filterBy(HomeScreenFragment.kt:76)
at XXXXXX.ui.home.homeScreen.HomeScreenFragment$initViews$5.onClick(HomeScreenFragment.kt:56)
If i try to print the id of Fragment, i obtain 2 different ids from method call showOnlyThisLevel() and onBackPressed(). What i miss ?
After doing some research, it seems that the problem stems from the misnaming of FragmentPagerAdapter's method - being named getItem(), but not clearly specifying that the abstract method getItem(int position) is supposed to return a new instance of a fragment rather than just "get an instance of one".
Of course, there is not much we can do about an incorrect name after it's been out in the wild for 7 years, but at least we can fix the bug that stems from this issue in your code ;)
Without further ado, the cause of your NPE is that onCreateView (where your Presenter is instantiated) is never called.
This happens because you are creating the fragment here:
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
...
homeFragment = HomeScreenFragment.newInstance()
incidentFragment = IncidentScreenFragment.newInstance()
}
You return this fragment from inside getItem(int position) in your FragmentPagerAdapter:
override fun getItem(position: Int): Fragment = when(position) {
...
1 -> activity.incidentFragment
...
}
So what we know about activity.incidentFragment is that in it, onCreateView() is never called.
This is caused by the fact that it's never actually added to a FragmentManager and never displayed on the screen.
That's because super.onCreate(savedInstanceState) in Activity recreates all Fragments, using their no-args constructor, via reflection, while keeping their tag (see findFragmentByTag).
So as you can see in this answer, or as I can quote here:
// Do we already have this fragment?
String name = makeFragmentName(container.getId(), itemId);
Fragment fragment = mFragmentManager.findFragmentByTag(name);
if (fragment != null) {
if (DEBUG) Log.v(TAG, "Attaching item #" + itemId + ": f=" + fragment);
mCurTransaction.attach(fragment);
} else {
fragment = getItem(position);
if (DEBUG) Log.v(TAG, "Adding item #" + itemId + ": f=" + fragment);
mCurTransaction.add(container.getId(), fragment,
makeFragmentName(container.getId(), itemId));
The getItem(position) method is only called if the Fragment is not found by the fragment tag that the FragmentPagerAdapter sets for the fragment, which IS automatically recreated after low memory condition kills your app.
Therefore, YOUR new fragment (that you create by hand in the Activity) is NEVER used, and therefore it has no view, never initialized, never added to FragmentManager, it's not the same instance as what's actually inside your ViewPager, and it crashes when you call it. Boom!
Solution is to instantiate the Fragment inside FragmentPagerAdapter's getItem(position) method. To get an instance of the fragment, use this answer.
Maybe this is a stupid question, but this is ruining my day...
I have a recyclerview in a fragment
override fun setUpRecyclerView(pics: List<Pictures>) {
recyclerView.setHasFixedSize(true)
layoutManager = LinearLayoutManager(context)
recyclerView.setLayoutManager(layoutManager)
mAdapter = NewsAdapter(pics, childFragmentManager)
recyclerView.setAdapter(mAdapter)
}
the NewsAdapter is:
class NewsAdapter
(private val mDataset: List<Pictures>, private val fragmentManager: FragmentManager)
: RecyclerView.Adapter<NewsAdapter.ViewHolder>() {
class ViewHolder(v: View) : RecyclerView.ViewHolder(v) {
var authorTextView: TextView
var viewPager: ViewPager
var indicator: CircleIndicator
init {
authorTextView = v.findViewById<View>(R.id.tv_author) as TextView
viewPager = v.findViewById<View>(R.id.viewPager) as ViewPager
indicator = v.findViewById<View>(R.id.indicator) as CircleIndicator
}
}
override fun onCreateViewHolder(parent: ViewGroup,
viewType: Int): NewsAdapter.ViewHolder {
val v = LayoutInflater.from(parent.context)
.inflate(R.layout.item_preview, parent, false)
return ViewHolder(v)
}
override fun onBindViewHolder(holder: ViewHolder, position: Int) {
val pictureList = mDataset.get(position)
holder.titleTextView.text = pictureList.title
holder.authorTextView.text = pictureList.author
showContent(pictureList.content, holder.viewPager, holder.indicator)
}
fun showContent(contentModel: List<ContentModel>, viewPager: ViewPager, indicator: CircleIndicator) {
if (contentModel.size <= 1) {
indicator.hide()
}
viewPager.adapter = GalleryContentAdapter(fragmentManager, contentModel)
indicator.setViewPager(viewPager)
}
override fun getItemCount(): Int = mDataset.size
}
the GalleryContentAdapter is:
class GalleryContentAdapter(fm: FragmentManager, val contentModels: List<ContentModel>) : FragmentPagerAdapter(fm) {
val galleryContentFactory: GalleryContentFactory = GalleryContentFactory()
override fun getItem(position: Int): Fragment = galleryContentFactory.getFragment(contentModels[position])
override fun getCount(): Int = contentModels.size
}
From now I am only handling a kind of content and the factory is so easy, but this is the code:
class GalleryContentFactory {
fun getFragment(contentModel: ContentModel): Fragment {
when (contentModel.type) {
"PICTURE" -> return PictureFragment.newInstance(contentModel.value)
}
return PictureFragment.newInstance(contentModel.value)
}
}
and the last is the PictureFragment:
class PictureFragment : NewsContentFragment() {
companion object {
val KEY = "PictureFragment.URL"
fun newInstance(url: String): NewsContentFragment {
val fragment = PictureFragment()
val bundle = Bundle()
bundle.putString(KEY, url)
fragment.arguments = bundle
return fragment
}
}
override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?): View? {
return inflater.inflate(R.layout.fragment_news_gif, container, false)
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
arguments?.getString(KEY).let {
view.image.loadUrl(it!!)
}
}
}
When I debug the code, I check that the line view.image.loadUrl(it!!) is being executed, but nothing is rendered.
The loadUrl method is a extended function of imageviews that loads an image using Glide like this
fun ImageView.loadUrl(url: String) {
GlideApp.with(context).load(url).into(this)
}
and is being called correctly.
I also tried with PagerStateAdapter and take into account that I am passing the ChildFragmentManager to the adapter of the ViewPager.
If you can help me, you will save my day. Thanks in advance
This doesn't work. The way to go is a recycler into a recycler. If you want simulate as a ViewPager, you may use https://github.com/rubensousa/RecyclerViewSnap with a MATCH_PARENT in the
child views.