ListView: 1st Item of the listview affects its last item

Question

i have a listview populated by two button and a textview. The problem is that every time I change the value to the last textview of my listview it resets the first, and if I change the first it resets the last. I also tried to use the tags and then compare them, but it doesn't work anyway. I don't understand where the problem is. Could anyone help me?

public class ProductListAdapterforListView extends BaseAdapter {
    private Context mContext;
    private List<piatto> mProductList;
    private LayoutInflater inflater = null;
    int[] bStatus;

    public ProductListAdapterforListView(Context mContext, List<piatto> mProductList) {
        this.mContext = mContext;
        this.mProductList = mProductList;
        inflater = (LayoutInflater) mContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        bStatus = new int[mProductList.size()];

    }
    @Override
    public int getCount() {
        return mProductList.size();
    }

    @Override
    public Object getItem(int position) {
        return mProductList.get(position);
    }

    @Override
    public long getItemId(int position) {
        return position;
    }


    @Override
    public View getView(final int position, View convertView, ViewGroup parent) {
        Viewholder viewholder;
        View row=convertView;
        if (row == null){
            viewholder=new Viewholder();

            row=inflater.inflate(R.layout.row_data_list, parent, false);


            viewholder.nome= (TextView) row.findViewById(R.id.namepiatto);
            viewholder.imageView= (ImageView) row.findViewById(R.id.imagepiatto);
            viewholder.prezzo= (TextView) row.findViewById(R.id.prezzopiatto);
            viewholder.btntakemore=(Button) row.findViewById(R.id.takemore);
            viewholder.btntakeless=(Button) row.findViewById(R.id.takeoff);
            viewholder.textViewcount=(TextView) row.findViewById(R.id.count);

            viewholder.btntakemore.setTag(position);
            viewholder.btntakeless.setTag(position);
            viewholder.textViewcount.setTag(position);

            row.setTag(viewholder);

        } else {
            viewholder = (Viewholder) row.getTag();
        }

        viewholder.nome.setText(mProductList.get(position).getNome());
        viewholder.prezzo.setText(mProductList.get(position).getPrezzo());
        Picasso.get().load(mProductList.get(position).getImmagine()).into(viewholder.imageView);

        viewholder.btntakemore.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                int v= (int) viewholder.btntakemore.getTag();
                int v1= (int) viewholder.textViewcount.getTag();

                if (v==v1){
                    int val= Integer.parseInt(String.valueOf(viewholder.textViewcount.getText()));
                    if (val < 5){
                        val=val + 1;
                        viewholder.textViewcount.setText(String.valueOf(val));
                        notifyDataSetChanged();
                    }
                }

            }
        });


        viewholder.btntakeless.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                int v= (int) viewholder.btntakeless.getTag();
                int v1= (int) viewholder.textViewcount.getTag();

                if (v==v1){
                    int val= Integer.parseInt(String.valueOf(viewholder.textViewcount.getText()));
                    if (val < 5){
                        val=val + 1;
                        viewholder.textViewcount.setText(String.valueOf(val));
                        notifyDataSetChanged();
                    }
                }
            }
        });

        return row;
    }

    public class Viewholder {
        TextView nome;
        TextView prezzo;
        ImageView imageView;
        Button btntakemore, btntakeless;
        TextView textViewcount;
    }

}