How to detect if RecyclerView is empty?

Question

I have a RecyclerView getting external JSON data parsed from a server. It works fine however the Volley async task on JSON sometimes takes a while and when it does the fragm

Answer 1

How is described in https://developer.android.com/training/material/lists-cards.html

The overriden method getItemCount() is invoked by the layout manager. This is the snippet:

// Return the size of your dataset (invoked by the layout manager)
@Override
public int getItemCount() {
    return mDataset.length;
}

So to detect if the recyclerView is empty you must request it to your LayoutManager. Example:

if( mLayoutManager.getItemCount() == 0 ){
    //Do something
}

I try to getItemCount() of my Adapter but this returns 0, I don't know why it is...

Answer 2

if (adapter.getItemCount() == 0)

doing this worked for me...

Answer 3

You can do it using interface callback:

1. Create interface

public interface OnAdapterCountListener {
    void onAdapterCountListener(int count);
}

2. Add below variables and methods in adapter

private OnAdapterCountListener onAdapterCountListener; 
    public void setOnAdapterCountListener(OnAdapterCountListener l) { 
        onAdapterCountListener = l; 
    }

3. Add this line in onCreateViewHolder of your adapter

onAdapterCountListener.onAdapterCountListener(getItemCount());

4. Finally, call interface in your activity

listAdapter.setOnAdapterCountListener(new OnAdapterCountListener() {
    @Override 
    public void onAdapterCountListener(int count) { 
        if (count > 0) 
            adapterEmptyText.setVisibility(View.GONE); 
    }
});

Answer 4

You can check if it's empty by running:

if (adapter.getItemCount() == 0)

If it's not working it means you haven't Override the getItemCount on your adapter! so make sure it's overrided:

@Override
public int getItemCount() {
    return mDataSet.size(); // Where mDataSet is the list of your items
}

Update: So based on your update this is how you could proceed. In my opinion you just need a callback. You are checking if the list is empty on your onViewCreated. You should, instead, use a callback. Do something like that:

public void onViewCreated(View view, Bundle savedInstanceState) {
    super.onViewCreated(view, savedInstanceState);
    LinearLayoutManager layoutManager = new LinearLayoutManager(getActivity());
    layoutManager.setOrientation(LinearLayoutManager.VERTICAL);
    layoutManager.supportsPredictiveItemAnimations();
    recyclerView.setLayoutManager(layoutManager);
    recyclerView.setItemAnimator(new DefaultItemAnimator());
    recyclerView.setClickable(true);
    recyclerView.setHasFixedSize(true);
    recyclerView.addItemDecoration(new DividerItemDecoration(getActivity(), DividerItemDecoration.VERTICAL_LIST));

    pDialog = new ProgressDialog(getActivity());
    pDialog.setMessage("Retrieving data from Server");
    pDialog.show();   
}

In the class you are using to populate your jsonList, I assume an asynctask or a separate class add this:

private OnJsonLoaded mListener;

public void setOnJsonLoadedListener(OnJsonLoaded listener) {
    mListener = listener;
}

public interface OnJsonLoaded {
    void onJsonLoaded(ArrayList<HashMap<String, String>> list);
}

now, in the asynctask that populate ur jsonLise or when the json parser finish his job, call the listener:

if (mListener != null) {
    mListener.onJsonLoaded(jsonList);
}

In your fragment (the one with NovaAdapter novaAdapter = new NovaAdapter(getActivity(),jsonList); and your recyclerview) add the interface implementation:

classThatParseJson.setOnJsonLoadedListener(new OnJsonLoaded() {
        @Override
        public void onJsonLoaded(ArrayList<HashMap<String, String>> list) {
            if (list.size() != 0) {
                NovaAdapter novaAdapter = new NovaAdapter(getActivity(),jsonList); 
                recyclerView.setAdapter(novaAdapter);
            } else {
                // Show something like a dialog that the json list is 0 or do whatever you want... here the jsonlist have a count of 0 so it's empty!
            }  
        }
});

the code may containts errors, i written it by hand without using IDE so maybe you have to fix small things but the logic is quite clear!

Update based on your Update 2:

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    View rootView = inflater.inflate(R.layout.fragment_subnets, container, false);
    recyclerView = (RecyclerView)rootView.findViewById(R.id.subnetsRV);
    return rootView;
}

@Override
public void onViewCreated(View view, Bundle savedInstanceState) {
    super.onViewCreated(view, savedInstanceState);
    LinearLayoutManager layoutManager = new LinearLayoutManager(getActivity());
    layoutManager.setOrientation(LinearLayoutManager.VERTICAL);
    layoutManager.supportsPredictiveItemAnimations();
    recyclerView.setLayoutManager(layoutManager);
    recyclerView.setItemAnimator(new DefaultItemAnimator());
    recyclerView.setClickable(true);
    recyclerView.setHasFixedSize(true);
    recyclerView.addItemDecoration(new DividerItemDecoration(getActivity(), DividerItemDecoration.VERTICAL_LIST));

    // start json parser here instead of passing to fragment as a bundle
    SubnetsParser.parseJSON(yourparams);
}

@Override
public void onJsonLoaded(ArrayList<HashMap<String, String>> list) {

    SubnetsParser.setOnJSONLoadedListener(new OnJSONLoaded() {
        @Override
        public void onJsonLoaded(ArrayList<HashMap<String, String>> list) {
            if (list.size() != 0){
                SubnetsAdapter subnetsAdapter = new SubnetsAdapter(getActivity(),jsonList);
                recyclerView.setAdapter(subnetsAdapter);
            }else {
                //pDialog = new ProgressDialog(getActivity());
                //pDialog.setMessage("Retrieving data from Server");
                //pDialog.show();
                //Instead of a progressdialog, put here a dialog informing that the list is empty!
            }
        }
    });

}