价格错误更新

Question

我对购物车中单件商品的总价更新错误。如果我增加数量并减少数量，则会发生以下情况：

增加数量1=4,10； 2=4,10； 3=8,20； 4=12,30；减少数量：从 4(16,30) 到 3 = 16,40； 2 = 12,30； 1=8,20;

但所有商品的总价是正确的。

public class CartAdapter extends RecyclerView.Adapter<CartViewHolder> {

private List<Order> listData = new ArrayList<>();
private Cart cart;

public CartAdapter(List<Order> listData, Cart cart) {
    this.listData = listData;
    this.cart = cart;
}
@NonNull
@Override
public CartViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
    LayoutInflater inflater = LayoutInflater.from(cart);
    View itemView = inflater.inflate(R.layout.cart_layout, parent, false);
    return new CartViewHolder(itemView);
}

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


    holder.btn_quantity.setNumber(listData.get(position).getQuantity());
    holder.btn_quantity.setOnValueChangeListener(new ElegantNumberButton.OnValueChangeListener() {
        @Override
        public void onValueChange(ElegantNumberButton view, int oldValue, int newValue) {

            Locale locale = new Locale("de", "DE");
            NumberFormat fmt = NumberFormat.getCurrencyInstance(locale);
            double price = (Double.parseDouble(listData.get(position).getPrice()))*(Double.parseDouble(listData.get(position).getQuantity()));
            //int price = (Integer.parseInt(listData.get(position).getPrice()))*(Integer.parseInt(listData.get(position).getQuantity()));
            holder.txt_price.setText(fmt.format(price));
            holder.txt_cart_name.setText(listData.get(position).getProductName());

            Order order = listData.get(position);
            order.setQuantity(String.valueOf(newValue));
            new Database(cart).updateCart(order);

            double total = 0;
            List<Order> orders = new Database(cart).getCarts();
            for (Order item:orders)
                total+=(Double.parseDouble(order.getPrice()))*(Integer.parseInt(item.getQuantity()));

            cart.txtTotalPrice.setText(fmt.format(total));
        }
    });

    Locale locale = new Locale("de", "DE");
    NumberFormat fmt = NumberFormat.getCurrencyInstance(locale);
    double price = (Double.parseDouble(listData.get(position).getPrice()))*(Double.parseDouble(listData.get(position).getQuantity()));
    //int price = (Integer.parseInt(listData.get(position).getPrice()))*(Integer.parseInt(listData.get(position).getQuantity()));
    holder.txt_price.setText(fmt.format(price));
    holder.txt_cart_name.setText(listData.get(position).getProductName());
}


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

Answer 1

可能问题出在代码的顺序上，你应该把这段代码：

Order order = listData.get(position);
order.setQuantity(String.valueOf(newValue));
new Database(cart).updateCart(order);

在开头：

public void onValueChange(ElegantNumberButton view, int oldValue, int newValue) {
  // event listener code
}

这个块。

希望对你有帮助:)