How to show empty view reliably for RecyclerView only when RealmResults is empty

Question

I understand there are a lot of information about it out there, but I haven't found one that matches my case yet.

I have a recycleview on a fragment that is always open, so the fragment basically never re-creates itself.

This is my code to load the adapter.

    reLoad(); //method shown below
    mRecycler.setAdapter(new SolicitationAdapter(myRealm.where(SolicitationDatabase.class).findAllAsync()));

And this is the logic I came up with:

public void reLoad() {
    if (!myRealm.where(SolicitationDatabase.class).findAll().isEmpty()) {
        mNothingHere.setVisibility(View.GONE);
        mRecycler.setVisibility(View.VISIBLE);
    } else {
        mNothingHere.setVisibility(View.VISIBLE);
        mRecycler.setVisibility(View.GONE);
    }
}

It works great the first time the user opens the app.

The trouble starts when the user creates a record, since the fragment doesn't re-create itself it never reloads.

The reason I haven't been able to reload after user adds something is because the method to add a new record is on a singleton being called from a different activity. Which means when I try to do it I get a nullpointerexception when declaring the the recycleview and the textview.

Edit - What I tried (reloading views from another place)

I have a class called PostHelper, this class is in charge of posting a new record.

This is the constructor:

public PostHelper(Context context, Activity activity) {
    this.mContext = context;
    this.mActivity = activity; //I call this in order to use "findViewById"

This is where the post happens:

public String addSolicitation(File _file, boolean fromQueue) {
//loading view
    TextView nothingHere = (TextView) mActivity.findViewById(R.id.nothing_here);
    RecyclerView recycler = (RecyclerView) mActivity.findViewById(R.id.recycler);
...so on until after the post:
SolicitationAdapter n = new SolicitationAdapter(myRealm.where(SolicitationDatabase.class).findAll());
n.notifyDataSetChanged();

nothingHere.setVisibility(View.GONE);
recycler.setVisibility(View.VISIBLE);

And this is the stacktrace:

06-01 21:43:37.511 9122-9122/? E/AndroidRuntime: FATAL EXCEPTION: main
                                             Process: com.example.ga.realm3, PID: 9122
                                             io.reactivex.exceptions.OnErrorNotImplementedException: Attempt to invoke virtual method 'void android.widget.TextView.setVisibility(int)' on a null object reference

Edit 2 - I load PostHelper class using the following:

mPostHelper = new PostHelper(this, PostSolicitationActivity.this);

Answer 1

You're supposed to make sure that SolicitationAdapter is a RealmRecyclerViewAdapter, like so:

public class SolicitationAdapter extends RealmRecyclerViewAdapter<SolicitationDatabase, SolicitationViewHolder> {
     public SolicitationAdapter(OrderedRealmCollection<SolicitationDatabase> results) {
         super(results, true);
     }
 ...
}

And then what you need to do is that you put the RealmResults as a field reference in your Activity:

public class PostSoliticiationActivity extends AppCompatActivity {
     RealmResults<Solicitation> results;
     Realm realm;
     RealmChangeListener<RealmResults<Solicitiation> realmChangeListener = (results) -> {
         if(results.isLoaded() && results.isValid()) {
            if(results.isEmpty()) {
                mNothingHere.setVisibility(View.GONE);
                mRecycler.setVisibility(View.VISIBLE);
            } else {
                mNothingHere.setVisibility(View.VISIBLE);
                mRecycler.setVisibility(View.GONE);
            }
         }
     }

     SolicitationAdapter adapter;

     @Override
     protected void onCreate(Bundle bundle) {
         super.onCreate(bundle);
         setContentView(R.layout.soliticiation_activity);
         // bind views 
         realm = Realm.getDefaultInstance();
         results = realm.where(SolicitationDatabase.class).findAllSortedAsync("id");
                                // .sort("id").findAllAsync(); in 4.3.0+
         results.addChangeListener(realmChangeListener);
         adapter = new SoliticiationAdapter(results);
         mRecycler.setAdapter(adapter);
         // layout manager as well
     }

     @Override
     public void onDestroy() {
         results.removeChangeListener(realmChangeListener);
         realm.close();
         super.onDestroy();
     }
}

---

So things you don't need:

1.) reLoad() method

2.) onPostAdded callback

3.) PostActionListener

As long as you just add the SoliticiationDatabase to the Realm in a transaction, it'll all work without manually syncing ui.