Estoy tratando de desarrollar un tipo de aplicación de comercio electrónico en la que el usuario pueda agregar un artículo al carrito. Pero no puedo actualizar el contador de la insignia del carrito desde el adaptador. Aquí hay una captura de pantalla de mi aplicación.

Estoy usando la vista Recycler dentro del fragmento. Y me refiero a este enlace a continuación para el recuento de elementos del menú.

https://mobikul.com/adding-badge-count-on-menu-items-like-cart-notification-etc/

Mi problema es que no puedo acceder al elemento del menú desde el adaptador.

Aquí está mi código de fragmento.

PriceListFragment.java

public class PriceListFragment extends Fragment {

    public ArrayList<Design> designList;
    private Single_DesignAdapter adapter;
    private RecyclerView recyclerView;

    public PriceListFragment() {
        // Required empty public constructor
    }

    @Override
    public View onCreateView(LayoutInflater inflater, final ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        setHasOptionsMenu(true);
        View v = inflater.inflate(R.layout.fragment_price_list, container, false);

        recyclerView = (RecyclerView)v.findViewById(R.id.pl_recycler_view);

        designList = new ArrayList<Design>();

        designList = list();

        recyclerView.setLayoutManager(new LinearLayoutManager(getContext()));
        recyclerView.setHasFixedSize(true);
        adapter = new Single_DesignAdapter(getContext(), designList);
        recyclerView.setAdapter(adapter);

        return v;
    }

    @Override
    public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
        inflater.inflate(R.menu.cart_menu, menu);
        super.onCreateOptionsMenu(menu, inflater);

        MenuItem itemCart = menu.findItem(R.id.menu_cart);
        LayerDrawable icon = (LayerDrawable) itemCart.getIcon();
        setBadgeCount(getContext(), icon, 0);
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()) {

            case R.id.menu_cart:
                Toast.makeText(getActivity(), "cart", Toast.LENGTH_SHORT). show();
                return false;


            default:
                break;
        }
        return false;

    }

    public ArrayList<Design> list() {
        ArrayList<Design> arrayList = new ArrayList<Design>();

        Design design = new Design();
        design.name = "Black";
        design.image = "http://website/Demo/images/1.jpg";
        design.designName = "11001";
        design.qualityName = "Cotton";
        design.amount = "1000";
        design.discPercent = "5";

        Design design2 = new Design();
        design2.name = "Green";
        design2.image = "http://website/Demo/images/2.jpg";
        design2.designName = "11001";
        design2.qualityName = "Cotton";
        design2.amount = "900";
        design2.discPercent = "9";

        arrayList.add(design);
        arrayList.add(design2);

        return arrayList;
    }

    public static void setBadgeCount(Context context, LayerDrawable icon, int count) {

        BadgeDrawable badge;

        // Reuse drawable if possible
        Drawable reuse = icon.findDrawableByLayerId(R.id.ic_badge);
        if (reuse != null && reuse instanceof BadgeDrawable) {
            badge = (BadgeDrawable) reuse;
        } else {
            badge = new BadgeDrawable(context);
        }

        badge.setCount(count);
        icon.mutate();
        icon.setDrawableByLayerId(R.id.ic_badge, badge);
    }
}

El diseño es mi clase de modelo

Design.java

public class Design implements Serializable{

    public String id;
    public String qualityId;
    public String qualityName;
    public String designId;
    public String designName;
    public String image;
    public String name; //use as shade name
    public String discPercent;
    public String amount;
    public String pcs;
    public String qty;
}

Single_DesignAdapter.java

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

    public ArrayList<Design> designList;
    private Context context;
    private LayoutInflater layoutInflater;

    public Single_DesignAdapter(Context context, ArrayList<Design> designList) {
        this.designList = designList;
        this.context = context;
        this.layoutInflater = LayoutInflater.from(context);
    }

    @Override
    public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View view = layoutInflater.inflate(R.layout.single_design, parent, false);
        return new ViewHolder(view);
    }

    @Override
    public void onBindViewHolder(final ViewHolder holder, int position) {

        Design design = designList.get(position);
        holder.tvQuality.setText(design.qualityName);
        holder.tvDesign.setText(design.designName);
        holder.tvShade.setText(design.name);
        if (!design.discPercent.equals("0")) {
            holder.tvDisPer.setText("-"+design.discPercent+"%");
            holder.tvAmount.setPaintFlags(holder.tvAmount.getPaintFlags() | Paint.STRIKE_THRU_TEXT_FLAG);
            int a = Integer.parseInt(design.amount);
            float b = Float.parseFloat(design.discPercent) / 100;
            holder.tvAmount.setText("₹ " + design.amount);
            int c = (int) (a * b);
            int d = a-c;
            holder.tvDiscAmt.setText("₹ " +d);
            Picasso.with(context).load(design.image).into(holder.ivDesign);
        } else {
            holder.tvAmount.setText("₹ " + design.amount);
            Picasso.with(context).load(design.image).into(holder.ivDesign);
            holder.tvDisPer.setVisibility(View.INVISIBLE);
            holder.tvDiscAmt.setVisibility(View.INVISIBLE);
        }

        holder.btAdd.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                holder.llAdd.setVisibility(View.GONE);
                holder.llPlusMinus.setVisibility(View.VISIBLE);
            }
        });

        holder.btPlus.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                if (Integer.parseInt(holder.btPcsCount.getText().toString()) >= 1) {
                    int a = Integer.parseInt(holder.btPcsCount.getText().toString());
                    int x = a++;
                    holder.btPcsCount.setText(Integer.toString(a));
                }
            }
        });

        holder.btMinus.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                if (Integer.parseInt(holder.btPcsCount.getText().toString()) <= 1) {
                    holder.llAdd.setVisibility(View.VISIBLE);
                    holder.llPlusMinus.setVisibility(View.GONE);
                } else {
                    int a = Integer.parseInt(holder.btPcsCount.getText().toString());
                    a--;
                    holder.btPcsCount.setText(Integer.toString(a));
                }
            }
        });

    }

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

    public class ViewHolder extends RecyclerView.ViewHolder {

        public LinearLayout llPer, llAdd, llPlusMinus;
        public Button btPlus, btMinus, btPcsCount, btAdd;
        public ImageView ivDesign;
        public TextView tvDesign, tvQuality, tvShade, tvAmount, tvDiscAmt, tvDisPer;

        public ViewHolder(View itemView) {
            super(itemView);

            btPlus = (Button) itemView.findViewById(R.id.btPlus);
            //other find view by ids
        }
    }
}

Ahora, cuando el usuario agrega un artículo al carrito, debe aumentar el contador. Agregaré todos los artículos del carrito enArrayList<Design> y luego guardaré esta lista en preferencia compartida. Gestionaré todo, pero no puedo entender cómo puedo actualizar el contador del carrito desde el adaptador. No puedo acceder al menú en el adaptador. Si hay otra forma de hacerlo, por favor ayuda.