从backStack还原片段时RecyclerView为空

Question

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!

Answer 1

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