notifyDataSetChanged not working on RecyclerView

I am getting data from server and then parsing it and storing it in a List. I am using this list for the RecyclerView's adapter. I am using Fragments.

I am using a Nexus 5 with KitKat. I am using support library for this. Will this make a difference?

Here is my code: (Using dummy data for the question)

Member Variables:

List<Business> mBusinesses = new ArrayList<Business>();

RecyclerView recyclerView;
RecyclerView.LayoutManager mLayoutManager;
BusinessAdapter mBusinessAdapter;

My onCreateView():

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
		Bundle savedInstanceState) {

	// Getting data from server
	getBusinessesDataFromServer();

	View view = inflater.inflate(R.layout.fragment_business_list,
			container, false);
	recyclerView = (RecyclerView) view
			.findViewById(R.id.business_recycler_view);
	recyclerView.setHasFixedSize(true);

	mLayoutManager = new LinearLayoutManager(getActivity());
	recyclerView.setLayoutManager(mLayoutManager);

	mBusinessAdapter = new BusinessAdapter(mBusinesses);
	recyclerView.setAdapter(mBusinessAdapter);

	return view;
}

After getting data from server, parseResponse() is called.

protected void parseResponse(JSONArray response, String url) {
	// insert dummy data for demo

	mBusinesses.clear();

	Business business;

	business = new Business();
	business.setName("Google");
	business.setDescription("Google HeadQuaters");
	mBusinesses.add(business);

	business = new Business();
	business.setName("Yahoo");
	business.setDescription("Yahoo HeadQuaters");
	mBusinesses.add(business);

	business = new Business();
	business.setName("Microsoft");
	business.setDescription("Microsoft HeadQuaters");
	mBusinesses.add(business);

	Log.d(Const.DEBUG, "Dummy Data Inserted\nBusinesses Length: "
			+ mBusinesses.size());

	mBusinessAdapter = new BusinessAdapter(mBusinesses);
	mBusinessAdapter.notifyDataSetChanged();
}

My BusinessAdapter:

public class BusinessAdapter extends
	RecyclerView.Adapter<BusinessAdapter.ViewHolder> {

    private List<Business> mBusinesses = new ArrayList<Business>();

	// Provide a reference to the type of views that you are using
	// (custom viewholder)
	public static class ViewHolder extends RecyclerView.ViewHolder {
		public TextView mTextViewName;
		public TextView mTextViewDescription;
		public ImageView mImageViewLogo;

		public ViewHolder(View v) {
			super(v);
			mTextViewName = (TextView) v
					.findViewById(R.id.textView_company_name);
			mTextViewDescription = (TextView) v
					.findViewById(R.id.textView_company_description);
			mImageViewLogo = (ImageView) v
					.findViewById(R.id.imageView_company_logo);
		}
	}

	// Provide a suitable constructor (depends on the kind of dataset)
	public BusinessAdapter(List<Business> myBusinesses) {

		Log.d(Const.DEBUG, "BusinessAdapter -> constructor");

		mBusinesses = myBusinesses;
	}

	// Create new views (invoked by the layout manager)
	@Override
	public BusinessAdapter.ViewHolder onCreateViewHolder(ViewGroup parent,
			int viewType) {
		
		Log.d(Const.DEBUG, "BusinessAdapter -> onCreateViewHolder()");
		
		// create a new view
		View v = LayoutInflater.from(parent.getContext()).inflate(
				R.layout.item_business_list, parent, false);

		ViewHolder vh = new ViewHolder(v);
		return vh;
	}

	// Replace the contents of a view (invoked by the layout manager)
	@Override
	public void onBindViewHolder(ViewHolder holder, int position) {
		// - get element from your dataset at this position
		// - replace the contents of the view with that element
		
		Log.d(Const.DEBUG, "BusinessAdapter -> onBindViewHolder()");

		Business item = mBusinesses.get(position);
		holder.mTextViewName.setText(item.getName());
		holder.mTextViewDescription.setText(item.getDescription());
		holder.mImageViewLogo.setImageResource(R.drawable.ic_launcher);

	}

	// Return the size of your dataset (invoked by the layout manager)
	@Override
	public int getItemCount() {

		Log.d(Const.DEBUG, "BusinessAdapter -> getItemCount()");

		if (mBusinesses != null) {
			Log.d(Const.DEBUG, "mBusinesses Count: " + mBusinesses.size());
			return mBusinesses.size();
		}
		return 0;
	}
}

But I don't get the data displayed in the view. What am I doing wrong?

Here is my log,

07-14 21:15:35.669: D/xxx(2259): Dummy Data Inserted
07-14 21:15:35.669: D/xxx(2259): Businesses Length: 3
07-14 21:26:26.969: D/xxx(2732): BusinessAdapter -> constructor

I don't get any logs after this. Shouldn't getItemCount() in adapter should be called again?

In your parseResponse() you are creating a new instance of the BusinessAdapter class, but you aren't actually using it anywhere, so your RecyclerView doesn't know the new instance exists.

You either need to:

• Call recyclerView.setAdapter(mBusinessAdapter) again to update the RecyclerView's adapter reference to point to your new one
• Or just remove mBusinessAdapter = new BusinessAdapter(mBusinesses); to continue using the existing adapter. Since you haven't changed the mBusinesses reference, the adapter will still use that array list and should update correctly when you call notifyDataSetChanged().

Try this method:

List<Business> mBusinesses2 = mBusinesses;
mBusinesses.clear();
mBusinesses.addAll(mBusinesses2);
//and do the notification

a little time consuming, but it should work.

Just to complement the other answers as I don't think anyone mentioned this here: notifyDataSetChanged() should be executed on the main thread (other notify<Something> methods of RecyclerView.Adapter as well, of course)

From what I gather, since you have the parsing procedures and the call to notifyDataSetChanged() in the same block, either you're calling it from a worker thread, or you're doing JSON parsing on main thread (which is also a no-no as I'm sure you know). So the proper way would be:

protected void parseResponse(JSONArray response, String url) {
    // insert dummy data for demo
    // <yadda yadda yadda>
    mBusinessAdapter = new BusinessAdapter(mBusinesses);
    // or just use recyclerView.post() or [Fragment]getView().post()
    // instead, but make sure views haven't been destroyed while you were
    // parsing
    new Handler(Looper.getMainLooper()).post(new Runnable() {
        public void run() {
            mBusinessAdapter.notifyDataSetChanged();
        }
    });
    

}

PS Weird thing is, I don't think you get any indications about the main thread thing from either IDE or run-time logs. This is just from my personal observations: if I do call notifyDataSetChanged() from a worker thread, I don't get the obligatory Only the original thread that created a view hierarchy can touch its views message or anything like that - it just fails silently (and in my case one off-main-thread call can even prevent succeeding main-thread calls from functioning properly, probably because of some kind of race condition)

Moreover, neither the RecyclerView.Adapter api reference nor the relevant official dev guide explicitly mention the main thread requirement at the moment (the moment is 2017) and none of the Android Studio lint inspection rules seem to concern this issue either.

But, here is an explanation of this by the author himself

I had same problem. I just solved it with declaring adapter public before onCreate of class.

PostAdapter postAdapter;

after that

postAdapter = new PostAdapter(getActivity(), posts);
recList.setAdapter(postAdapter);

at last I have called:

@Override
protected void onPostExecute(Void aVoid) {
    super.onPostExecute(aVoid);
    // Display the size of your ArrayList
    Log.i("TAG", "Size : " + posts.size());
    progressBar.setVisibility(View.GONE);
    postAdapter.notifyDataSetChanged();
}

May this will helps you.

Although it is a bit strange, but the notifyDataSetChanged does not really work without setting new values to adapter. So, you should do:

array = getNewItems();                    
((MyAdapter) mAdapter).setValues(array);  // pass the new list to adapter !!!
mAdapter.notifyDataSetChanged();       

This has worked for me.

Clear your old viewmodel and set the new data to the adapter and call notifyDataSetChanged()

In my case, force run #notifyDataSetChanged in main ui thread will fix

public void refresh() {
        clearSelection();
        // notifyDataSetChanged must run in main ui thread, if run in not ui thread, it will not update until manually scroll recyclerview
        ((Activity) ctx).runOnUiThread(new Runnable() {
            @Override
            public void run() {
                adapter.notifyDataSetChanged();
            }
        });
    }

I always have this problem that I forget that the RecyclerView expects a new instance of a List each time you feed the adapter.

List<X> deReferenced = new ArrayList(myList);
adapter.submitList(deReferenced);

Having the "same" List (reference) means not declaring "new" even if the List size changes, because the changes performed to the List also propagates to other Lists (when they are simply declared as this.localOtherList = myList) emphasis on the keyword being "=", usually components that compare collections make a copy of the result after the fact and store it as "old", but not Android DiffUtil.

So, if a component of yours is giving the same List each and every time you submit it, the RecyclerView won't trigger a new layout pass. The reason is that... AFAIR, before the DiffUtil even attempts to apply the Mayers algorithm, there is a line doing a:

 if (newList == mList)) {return;}

I am not sure how much "good practice" does de-referencing within the same system is actually defined as "good" ... Specially since a diff algorithm is expected to have a new(revised) vs old(original) component which SHOULD in theory dereference the collection by itself after the process has ended but... who knows...?

But wait, there is more...

doing new ArrayList() dereferences the List, BUT for some reason Oracle decided that they should make a second "ArrayList" with the same name but a different functionality.

This ArrayList is within the Arrays class.

/**
     * Returns a fixed-size list backed by the specified array.  (Changes to
     * the returned list "write through" to the array.)  This method acts
     * as bridge between array-based and collection-based APIs, in
     * combination with {@link Collection#toArray}.  The returned list is
     * serializable and implements {@link RandomAccess}.
     *
     * <p>This method also provides a convenient way to create a fixed-size
     * list initialized to contain several elements:
     * <pre>
     *     List&lt;String&gt; stooges = Arrays.asList("Larry", "Moe", "Curly");
     * </pre>
     *
     * @param <T> the class of the objects in the array
     * @param a the array by which the list will be backed
     * @return a list view of the specified array
     */
    @SafeVarargs
    @SuppressWarnings("varargs")
    public static <T> List<T> asList(T... a) {
        return new ArrayList<>(a); //Here
    }

This write-through is funny because if you:

Integer[] localInts = new Integer[]{1, 2, 8};
Consumer<List<Integer>> intObserver;

public void getInts(Consumer<List<Integer>> intObserver) {
    this.intObserver = intObserver;
    dispatch();
}

private void dispatch() {
    List<Integer> myIntegers = Arrays.asList(localInts);
    intObserver.accept(myIntegers);
}
    

... later:

getInts(
    myInts -> {
    adapter.submitList(myInts); //myInts = [1, 2, 8]
    }
);
    

Not only does the List dispatched obeys the dereferencing on each submission, but when the localInts variable is altered,

public void set(int index, Integer value) {
    localInts[index] = value;
    dispatch(); // dispatch again
}

...

myModel.set(1, 4) // localInts = [1, 4, 8]

this alteration is also passed to the List WITHIN the RecyclerView, this means that on the next submission, the (newList == mList) will return "false" allowing the DiffUtils to trigger the Mayers algorithm, BUT the areContentsTheSame(@NonNull T oldItem, @NonNull T newItem) callback from the ItemCallback<T> interface will throw a "true" when reaching index 1. basically, saying "the index 1 inside RecyclerView (that was supposed to be 2 in th previous version) was always 4", and a layout pass will still not perform.

So, the way to go in this case is:

List<Integer> trulyDereferenced = new ArrayList<>(Arrays.asList(localInts));
adapter.submitList(trulyDereferenced);