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RecyclerView is empty when restoring fragment from backStack

I have a RecyclerView in a Fragment and initially is hidden. When user clicks a button, I set visibility to true for the RecyclerView and I display some data I have on an ArrayList.
The problem starts when I move another fragment on top (I add the previous fragment with the RecyclerView in the backStack) : if I click back from the new fragment the previous fragment (the one with the RecyclerView ) is visible and in onCreateView() I log the values of the dataSet I'm using for the recyclerView and everything is there, but the recyclerView is empty ( only footer item is presented ).
If we call RvFragment the Fragment with the RecyclerView and NextFragment the fragment that comes to the backstack and then leaves the schema is :
(back pressed)
RvFragment ----------> NextFragment ------------> RvFragment
and here's the code from onCreateView() :
#Nullable
#Override
public View onCreateView(final LayoutInflater inflater, #Nullable ViewGroup container, #Nullable Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_photo_comments, container, false);
ButterKnife.bind(this, view);
Timber.i("onCreateView data.size == %d", commentArrayList.size());
setToolbarTitle();
Picasso.with(getActivity())
.load(photo)
.placeholder(R.drawable.ic_timeline_image_placeholder)
.centerCrop()
.fit()
.into(ivPhoto);
if (hasCommentsVisible) {
Timber.i("comments are visible!! and dataSize == %d", commentArrayList.size());
llFlagsCommentsContainer.setVisibility(View.GONE);
rvCommentsList.setVisibility(View.VISIBLE);
}
tvComments.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
hasCommentsVisible = true;
llFlagsCommentsContainer.setVisibility(View.GONE);
rvCommentsList.setVisibility(View.VISIBLE);
}
});
initRecyclerView();
return view;
}
You can see with the log statements in the code above I can confirm the data exist. Thanks!

I'm not sure I understand how you set up your fragment stack but just to be sure : onCreateView won't be called again when you press the back button if the fragment is still on the stack.
https://developer.android.com/training/basics/fragments/fragment-ui.html#Replace
transaction.replace(R.id.fragment_container, newFragment);
transaction.addToBackStack(null);
Only onStart() will.
If you want onCreateView to be called again then you need to use the
FragmentTransaction.replace(NextFragment)
without the addToBackStack() but it means the whole fragment will be recreated from scratch. Probably not what you want, especially if you are getting your data from a webservice.
Alternatively, to fully recreate your fragment every time you come back to it, you can simply remove it entirely :
FragmentTransaction.remove(RvFragment)
and then push your next fragment

Why is fragment calling OnCreate / OnCreateView when using fragment transactions with FrameLayout?

The main page of my application has a FrameLayout.
I'm instantiating two fragments when the activity starts, and I'm trying to use a menu button to swap between the fragment.
scanHistoryFrag = new HistoryFragment();
scanFrag = new ScanFragment();
I never replace these objects - I use the same ones throughout the lifecycle of the application. However, when I swap them in my FrameLayout...
private void ChangeFragment(Android.Support.V4.App.Fragment fragment)
{
Android.Support.V4.App.FragmentTransaction ft = SupportFragmentManager.BeginTransaction();
ft.Replace(Resource.Id.fragmentContainer, fragment);
ft.Commit();
}
OnCreate and OnCreateView are called on the Fragment again... which means any adjustments I made post creation on that fragment are overwritten with initial values again. I can't seem to find any explanation for why this is happening or how I might avoid it.
The ChangeFragment method is being called by OnOptionsItemSelected, as I'm using a menu button to toggle them.

I never replace these objects - I use the same ones throughout the lifecycle of the application.
Initialization of a subclass of Fragment just create a instance of this class object, the constructor of this class will be called, but it will not go through the lifecycle of Fragment unless this Fragment is added, for more information, you can refer to Fragments. To understand it easier, I personal think the instance saves the data state of this Fragment class, but the events of lifecycle handle the view state of this Fragment.
which means any adjustments I made post creation on that fragment are overwritten with initial values again.
Yes, you're right. To avoid overwritting with initial values again, we can cache the fragment's view in OnCreateView for example like this:
private View rootView;
public override View OnCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
{
// Use this to return your custom view for this Fragment
// return inflater.Inflate(Resource.Layout.YourFragment, container, false);
if (rootView == null)
{
//first time creating this fragment view
rootView = inflater.Inflate(Resource.Layout.fragmentlayout1, container, false);
//Initialization
//TODO:
}
else
{
//not first time creating this fragment view
ViewGroup parent = (ViewGroup)rootView.Parent;
if (parent != null)
{
parent.RemoveView(rootView);
}
}
return rootView;
}

Android retaining information across fragments

I have five fragments a user can switch between. One of these fragments loads a list of users from the server to populate the UI list on the fragment. I need the list information to persist if a user swipes to a different fragment and then swipes back to the original. I do not want the fragment to reload the users every time a user leaves the fragment and goes back.
I am looking at setRetainInsance(true) and was wondering if this is possible solution? What would be the best way for the fragment to retain the information without being created from scratch each time.
I am using this to switch between fragements -getSupportFragmentManager().beginTransaction().replace(R.id.searchLayout, ratingFragment).commit();

A Fragment is Just like any other object.
on Fragment transaction , the Fragment does not call OnCreate() method instead it starts from onCreateView , therefore , load your users and save it an instance variable and assign it in onCreate()
Example
class MyFragment extends Fragment{
List<users> userList;
void onCreate(){
userList = getUserList();}
//the list is loaded during Oncreate();
now imagine you have replaced the Fragment
now According to Andorid Framework , onCreate() is not Called again
instead onCreateView() is called
void onCreateView(){
//you can check whether instance Variable is initialised or not
if(userList != null) {
listview.setAdapter(new Myadapter(this,userList);

Replace the fragment by adding it to backstack.
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.addToBackStack(tag);
fragmentTransaction.replace(container, fragment, tag);
fragmentTransaction.commit();
Also create object of View and return it if it's not null.
private void View view ;
#Override
public View onCreateView(LayoutInflater inflater, #Nullable ViewGroup container, #Nullable Bundle savedInstanceState) {
if (view != null)
return view;
view = inflater.inflate(R.layout.fragment_browse_recipe, container, false);
//initialize layout views
return view;
}

Null view after replacing fragment

Here's the problem
I have a Fragment class DisplayFragment and I already have one show in the content frame, then I do
DisplayFragment a = DisplayFragment.newInstance();
getSupportFragmentManager().beginTransaction()
.replace(R.id.contentFrame, DisplayFragment)
.commit();
Then I want to get the view of fragment a using View v = a.getView();, but it return a null view.
Can anyone tell me why? Cause I have to change some view setting of the new Fragment.
onCreateView() in DisplayFragment
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_display, container, false);
//Some TextView setup
Button button = (Button) view.fineViewById(R.id.button);
return view; }

You need to use delay or put your View v = a.getView(); in loop which will watch first that your fragment is successfully attached, created and added in your activity or not. For this you can check with this isAdded() and isInLayout() if both return true then only call getView()
Now why this, as you add/replace fragment with commit with will fragment will class will be execute first it'll be start Fragment life cycle that is onAttach(), onCreate(), onCreateView() and so on. Now you will getting null from getView() just because your view is not created still. Fragment Life Cycle. If you doubt regarding this let me know.

I assume that you call View v = a.getView(); right after commit?
Because getView method only return not null value after onCreateView returned.
In your case, after called commit(), it take time to complete all the lifecyle callback of DisplayFragment a (from onCreate -> onCreatedView,..).
So that, right after commit(), the getView method still return null.

Declare DisplayFragment a; as Class Reference. Because after commit you want to just access View v = a.getView(); it unavailable due to fragment Life Cycle. You can get after execute block of code.
Make sure you have to mentioned OnCreateView() Method on class DisplayFragment
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
if (container == null) {
// We have different layouts, and in one of them this
// fragment's containing frame doesn't exist. The fragment
// may still be created from its saved state, but there is
// no reason to try to create its view hierarchy because it
// won't be displayed. Note this is not needed -- we could
// just run the code below, where we would create and return
// the view hierarchy; it would just never be used.
return null;
}
Log.i("Right", "onCreateView()");
return inflater.inflate(R.layout.right, container, false);
}

I had same problem as like you.
As the transaction of fragment did not takes place immediately. Thats why sometime the findViewById() does not work properly. But we can execute the pending transaction by using executePendingTransactions() method. I have used following code in my project to execute the pedingTransactions.
Fragment f = (Fragment)(FragmentClass.class).newInstance();
FragmentManager fm = getSupportFragmentManager();
FragmentTransaction ft = fm.beginTransaction();
ft.replace(R.id.your_fragment_container_name,f).commit();
fm.executePendingTransactions(); //Notice the FragmentManager Class object

How to reuse fragment's view in Android?

I am creating a Fragment Activity with tabs. Now whenever i select a tab, corresponding fragment gets recreated and its
onCreateView()
method is called.
But what i want is to reuse the view of the fragment so that whenever a tab is selected system does not call
onCreateView()
of fragment instead it shows the previous view of the fragment if it exists.
Please reply soon.

You may want to show and hide the fragments instead of adding and removing them when selecting a tab.
For example:
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
if (frag.isAdded()) {
transaction.show(R.id.layout, frag);
} else {
transaction.add(R.id.layout, frag);
}
transaction.commit();

setOffScreenPageLimit() method can be used to set how many fragments you want to keep alive even if they are not visible to the user.

Try this, it works for screen rotation and should work for your situation as well:
1) When you add fragment for the first time, create it with name parameter:
getSupportFragmentManager()
.beginTransaction()
.replace(<containerID>, <fragment>, YOUR_FRAGMENT_NAME_CONST)
.commit();
2) When you need to find it:
YourFragmentType fragment;
fragment = (YourFragmentType) getSupportFragmentManager()
.findFragmentByTag(YOUR_FRAGMENT_NAME_CONST);
if (fragment != null){
//TODO set data to the existing fragment
}
else{
//TODO create and initialize your fragment
}
Edit:
You should differentiate Fragment object creation and onCreateView() being called.
It's right that you should avoid unnecessary object creation and so reuse fragments.On the other hand (as for my experience) it's better to adhere Android's onCreateView() politics to guarantee consistent user experience.
If you really want to save CPU time and avoid re-inflating complicated view (and settle all issues yourselves) - you may just check it is null like this:
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
// View
if (mView == null) {
mView = inflater.inflate(R.layout.your_fragment, container, false);
...
}
...
}