Synchronizing RecyclerView's getItemCount() with onCreateViewHolder

Question

This problem has been beaten a million times, but unfortunately, no answer on SO has helped solve my issue.

Fundamentally, my question is that, in a RecyclerView with a CardView in a Fragment, when and where should the following tasks be performed:

• Fetching data from a server to the local database on the user's device
• Processing the so-fetched local data
• Instantiating and setting the RecyclerView's adapter
• Calling the RecyclerView's notifyfDataSetChanged()

The RecyclerView in my implementation presently calls back only getItemCount(). onCreateViewHolder() and onBindViewHolder() are never getting called back. (I have seen this answer and a gazillion more.)

Here is the sequence of how its being done:

1. An AppCompatActivity instantiates a Fragment

2. The Fragment's layout contains a RelativeLayout with a toolbar and an include tag for a ViewPager. The ViewPager layout contains another include tag that sets a layout with a RecyclerView in a LinearLayout. The layout XML with the CardView is set in the RecyclerView's adapter:

       public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType)
   {
       Log.wtf(LOG_TAG, "Inside onCreateViewHolder()");
       View myView;
       LayoutInflater inflater;
       inflater = LayoutInflater.from(parent.getContext());
       myItemView = inflater.inflate(R.layout.my_row_layout, parent, false);
       MyViewHolder myViewHolderItem = new MyViewHolder(myItemView);
       return myViewHolderItem;
   }
   

3. There's no ScrollView in any layout

4. The Fragment's onCreate() calls a method to fetch data from a server

---

public void onCreate(Bundle savedInstanceState)
{
    super.onCreate(savedInstanceState);
    // Some cache processing
    args = getArguments();

    myDBHelper = MyDBHelper.getInstance(getActivity());
    Intent intent = getActivity().getIntent();
    // Search comes from search intent
    if (intent.getBooleanExtra(MyContract.MY_SEARCH_REQUEST, false))
    {
        ...            
        getDataFromCloud("", true);
        getDataFromLocalDB(false, item);
    } // of if search intent 
    // Plain intent
    else 
    {
        getDataFromCloud("item", false);
        getDataFromLocalDB(true, item);
    }
} // of onCreate()

5. This data gets populated into a local database on the user's device
6. Another method in the Fragment's onCreate()filters the local data into an ArrayList
7. This ArrayList is presented in the RecyclerView - CardView combo finally to the user.
8. notifyDataSetChanged() is called in the Fragment's onActivityCreated(). But the fact is, its not making a difference anywhere it is called from. Also, the adapter is instantiated in the onPostExecute() of the AsyncTask that creates the ArrayList for the CardView from the local database.

Here's the log that results on running the app:

01-03 08:47:34.546 13489-14033/com.my A/MyDBHelper class: Create View-1 query: CREATE VIEW 
01-03 08:47:34.562 13489-13489/com.my A/MyFragment: getItemCount: 0 
01-03 08:47:34.584 13489-14033/com.my A/MyDBHelper class: Create View-2 query: CREATE TABLE 
01-03 08:47:34.638 13489-13489/com.my A/MyFragment: getItemCount: 0
01-03 08:47:34.722 13489-13489/com.my A/MyFragment: getItemCount: 2
01-03 08:47:34.743 13489-13489/com.my A/MyFragment: getItemCount: 2

In the above log, the View-1 query fetches server data and the View-2 query processes the so-fetched local data.

I have log statements in the onCreateViewHolder() and onBindViewHolder(). As evident above, these methods are just not being invoked, despite a positive return from getItemCount(), which is the size of the ArrayList. The app just shows the toolbar, and an empty white card, despite there being two records or items to be shown.

Been staring at these logs for the past couple of days with no progress or clues. Many thanks in advance for your expert advice or pointers (and for saving what's left of my sanity)!

Answer 1

Finally, it was Jared Burrows's advice that drove the last nail in the coffin. BoyOboy, the only way to get it right is fight! (...almost always!)

Though I cannot pin-point what was going wrong, here's what I re-did:

1. Created a fresh new project with only the RecyclerView - CardView combo in a Fragment. Well worth the time and effort, in terms of the clarity it brought in.
2. Read-up this very good resource.
3. Switched back to the ListView implementation of my app, first got the CardView right, into the ListView
4. With a fresh new understanding of RecyclerView, systematically replaced all the ListView code with the RecyclerView counterpart
5. In the app, the custom RecyclerAdapter and ViewHolder live in their own, independent classes now
6. Was stuck for another couple of hours with the "RecyclerView: No Adapter attached; skipping layout” error; nothing was showing up in the Fragment. That's when Jared Burrows's advice pitched in.

The RecyclerView is now looking all hunky dory, waiting to throw up the next challenge: animation!