Its because of nature of RecyclerView.

RecyclerView tries to reuse (recycle) already drawn items(viewHolders) when drawing new items.

Since you get input from view which is recycled, it already has a value and continues to increase/decrease from that value.

All you need to do is to holder.quantity.setText(some default value); in onBindView method OR store the input in your model.

The problem is in the recyclerview, if the view in one of the items is changed then the view gets changed in another item. And it changes specifically in the 8th position after the position of the actual item that is to be changed. Say, I change the quantity or price of the item in position 1 then the quantity or price is also gets changed in position 1 + 8 = 9th item. I can’t figure out why this is occurring since I’m simply changing the view in the viewholder position. If anyone faced this kind of problem or has any solution it will be helpful. Thank you.

RecyclerView Layout:

<androidx.recyclerview.widget.RecyclerView
   android_id="@+id/product_recyclerview"
   android_layout_width="match_parent"
   android_layout_height="wrap_content"
   android_layout_marginTop="@dimen/_10sdp"
   android_visibility="visible"/>

Adapter:

public class ProductAdapter extends RecyclerView.Adapter<ProductAdapter.MyViewHolder> {

    private List<ProductItem> productItemList;
    private Context context;
    private ExpenseActivityContract.Presenter presenter;

    public ProductAdapter(Context context, ExpenseActivityContract.Presenter presenter, List<ProductItem> productItemList) {

        this.productItemList = productItemList;
        this.presenter = presenter;
        this.context = context;
    }

    public class MyViewHolder extends RecyclerView.ViewHolder {

        ImageView productImage;
        TextView productName, add;
        EditText quantity, price;
        ImageButton plus, minus;

        public MyViewHolder(View v) {

            super(v);

            productImage = v.findViewById(R.id.product_image);
            productName = v.findViewById(R.id.product_name);
            add = v.findViewById(R.id.add_product_btn);
            quantity = v.findViewById(R.id.quantity_input);
            price = v.findViewById(R.id.product_price_input);
            plus = v.findViewById(R.id.plus_qnty_btn);
            minus = v.findViewById(R.id.minus_qnty_btn);
        }
    }

    @Override
    public ProductAdapter.MyViewHolder onCreateViewHolder(ViewGroup parent,
                                                          int viewType) {

        View v = LayoutInflater.from(parent.getContext())
                .inflate(R.layout.product_item_layout, parent, false);

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

    @Override
    public long getItemId(int position) {

        return super.getItemId(position);
    }

    @Override
    public int getItemViewType(int position) {

        return super.getItemViewType(position);
    }

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

        holder.productName.setText(productItemList.get(position).getProductName());

        holder.plus.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {

                String input = holder.quantity.getText().toString();

                if(TextUtils.isEmpty(input)) {

                    holder.quantity.setText("1");
                }
                else {

                    double qnty = Double.parseDouble(input);
                    qnty = qnty + 1.00;
                    holder.quantity.setText(String.valueOf(qnty));
                }
            }
        });

        holder.minus.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {

                String input = holder.quantity.getText().toString();

                if(TextUtils.isEmpty(input)) {

                    holder.quantity.setText("0");
                }
                else {

                    double qnty = Double.parseDouble(input);

                    if(qnty > 1.0) {

                        qnty = qnty - 1.00;
                        holder.quantity.setText(String.valueOf(qnty));
                    }
                    else if(qnty >= 0.0 && qnty <= 1.0) {

                        holder.quantity.setText("0");
                    }
                }
            }
        });
    }

    @Override
    public int getItemCount() {

        return productItemList.size();
    }
}