Example of undo action for Android RecyclerView onSwipe.

PhotoAdapter.java

public class PhotoAdapter extends RecyclerView.Adapter<PhotoAdapter.PhotoViewHolder> implements View.OnClickListener {

    private ArrayList<Photo> photos;
    public ArrayList<Photo> photosToRemove;
    private OnItemClickListener onItemClickListener;

    private Context context;
   

    public PhotoAdapter(Context context, ArrayList<Photo> photos, Map<Integer, String> authors, int colHeigth) {
        this.photos = photos;
        this.context = context;
        this.photosToRemove = new ArrayList<>();
    }

    public void setOnItemClickListener(OnItemClickListener onItemClickListener) {
        this.onItemClickListener = onItemClickListener;
    }

    @Override
    public PhotoViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View v = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_myphotos, parent, false);
        v.setOnClickListener(this);
        BusProvider.getInstance().register(this);
        PhotoViewHolder photoViewHolder = new PhotoViewHolder(v);
        return photoViewHolder;
    }

    @Override
    public void onBindViewHolder(PhotoViewHolder holder, int position) {
        Photo photo = photos.get(position);
        String tempUrl = context.getFilesDir() + UrlBuilder.localCoverPhoto(photo.remoteId);

        Glide.with(context)
                .load(tempUrl)
                .centerCrop()
                .diskCacheStrategy(DiskCacheStrategy.ALL)
                .into(holder.photoCover);

        holder.itemView.setTag(photo);
    }

    @Override
    public void onViewRecycled(PhotoViewHolder holder) {
        super.onViewRecycled(holder);
        Glide.clear(holder.photoCover);
    }

    @Override
    public int getItemCount() {
        return photos.size();
    }

    @Override
    public void onClick(final View v) {
        // Give some time to the ripple to finish the effect
        if (onItemClickListener != null) {
            new Handler().postDelayed(new Runnable() {
                @Override public void run() {
                    onItemClickListener.onItemClick(v, (Photo) v.getTag());
                }
            }, 50);
        }

    }

    public void onItemRemove(final RecyclerView.ViewHolder viewHolder, final RecyclerView mRecyclerView) {

        final int adapterPosition = viewHolder.getAdapterPosition();
        final Photo mPhoto = photos.get(adapterPosition);

        Snackbar snackbar = Snackbar
                .make(mRecyclerView, context.getString(R.string.removed_from_device), Snackbar.LENGTH_LONG)
                .setAction(R.string.undo, new View.OnClickListener() {
                    @Override
                    public void onClick(View view) {
                        int mAdapterPosition = viewHolder.getAdapterPosition();
                        photos.add(mAdapterPosition, mPhoto);
                        notifyItemInserted(mAdapterPosition);
                        mRecyclerView.scrollToPosition(mAdapterPosition);
                        photosToRemove.remove(mPhoto);
                    }
                });
        snackbar.show();
        photos.remove(adapterPosition);
        notifyItemRemoved(adapterPosition);
        photosToRemove.add(mPhoto);
    }

    public static class PhotoViewHolder extends  RecyclerView.ViewHolder {
        ImageView photoCover;
    
        public PhotoViewHolder(View itemView) {
            super(itemView);
            photoCover = (ImageView) itemView.findViewById(R.id.catalog_photo_cover);
        }
    }

    public interface OnItemClickListener {

        void onItemClick(View view, Photo photo);

    }
}

PhotoFragment.java

public class PhotoFragment extends Fragment implements PhotoAdapter.OnItemClickListener {

    public static final String TAG = "PhotoFragment";
    private int colsNr;
    private ArrayList<Photo> photos;
    PhotoAdapter mAdapter;

    @Bind(R.id.catalog_rv)
    RecyclerView recyclerView;

    @Bind(R.id.catalog_empty_view)
    LinearLayout emptyView;

  
    public static PhotoFragment newInstance() {
        PhotoFragment fragment = new PhotoFragment();
        return fragment;
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        colsNr = getResources().getInteger(R.integer.main_grid_columns);
   
    }

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        super.onCreateView(inflater, container, savedInstanceState);
        View view = inflater.inflate(R.layout.fragment_store_main, container, false);
        ButterKnife.bind(this, view);

        GridLayoutManager gridLayoutManager = new GridLayoutManager(getContext(), colsNr);
        recyclerView.setLayoutManager(gridLayoutManager);

        return view;
    }

    @Override
    public void onResume() {
        super.onResume();
        photos = (ArrayList<Photo>) Photo.getAllDownloaded();
        refreshAdapter();
        if (photos.isEmpty()) {
            showEmptyView();
        }
        else {
            hideEmptyView();
            mAdapter = new PhotoAdapter(getContext(), photos, authorIndex, colHeigth);
            mAdapter.setOnItemClickListener(this);
            recyclerView.swapAdapter(mAdapter, false);
            ItemTouchHelper.Callback callback = new PhotoTouchHelper(mAdapter, recyclerView);
            ItemTouchHelper helper = new ItemTouchHelper(callback);
            helper.attachToRecyclerView(recyclerView);
        }
    }

    @Override
    public void onPause() {
        ArrayList<Integer> photoIds = new ArrayList<>();
        if (mAdapter != null) {
            if (mAdapter.photosToRemove != null) {
                for (Photo photo: mAdapter.photosToRemove){

                    photoIds.add(photo.remoteId);
                }
                Intent mServiceIntent = new Intent(getActivity(), PhotoRemoveService.class);
                mServiceIntent.putExtra(Constants.ARG_GUIDES_TO_DELETE, photoIds);
                getActivity().startService(mServiceIntent);
            }
        }

        super.onPause();
    }

   
    private void showEmptyView() {
        recyclerView.setVisibility(View.GONE);
        emptyView.setVisibility(View.VISIBLE);
    }

    private void hideEmptyView() {
        recyclerView.setVisibility(View.VISIBLE);
        emptyView.setVisibility(View.GONE);
    }

    @Subscribe
    public void onEmptyPhotos(MyPhotosEmptyEvent event) {
        Log.d(TAG, "list is empty");
        showEmptyView();
    }


    @Override
    public void onItemClick(View view, Photo photo) {
        //@TODO do some action
    }

   
}

PhotoTouchHelper.java

public class PhotoTouchHelper  extends ItemTouchHelper.SimpleCallback {
    private PhotoAdapter mAdapter;
    private RecyclerView mRecyclerView;

    public GuideTouchHelper(PhotoAdapter adapter, RecyclerView recyclerView){
        super(ItemTouchHelper.UP | ItemTouchHelper.DOWN, ItemTouchHelper.LEFT | ItemTouchHelper.RIGHT);
        this.mAdapter = adapter;
        mRecyclerView = recyclerView;
    }

    @Override
    public boolean onMove(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, RecyclerView.ViewHolder target) {
        return true;
    }

    @Override
    public void onSwiped(RecyclerView.ViewHolder viewHolder, int direction) {
        mAdapter.onItemRemove(viewHolder, mRecyclerView);
    }
}

int mAdapterPosition = viewHolder.getAdapterPosition(); return always -1. I've used the previous int istead. final int adapterPosition = viewHolder.getAdapterPosition();

So, my code is:
.... public void onClick(View view) { productsList.add(adapterPosition, mPhoto); notifyItemInserted(adapterPosition); recyclerView.scrollToPosition(adapterPosition); productsRem.remove(mPhoto); }

The UNDO function now is fine