如何在JTable中添加/删除行后如何增加和减去值

Question

我有用于为我的JTable添加和删除单行的代码，但是它引起了一些问题，例如从JTable中删除后，无法提供准确的总和与减法计算。 JTable用作“购物车”，用于添加和删除购物车中的物品。

用于在购物车中添加一行的add to cart按钮：

if (e.getSource() == movebutton) {
        TableModel model1 = productTable.getModel();
        int index[] = productTable.getSelectedRows();
        Object[] row = new Object[4];
        DefaultTableModel model2 = (DefaultTableModel) cartTable.getModel();

        for (int i = 0; i < index.length; i++) {
            row[0] = model1.getValueAt(index[i], 0);
            row[1] = model1.getValueAt(index[i], 1);
            row[2] = model1.getValueAt(index[i], 2);
            model2.addRow(row);
            getSum();
        }

添加全部项目的代码：

public void getSum() {  //column 02 is where the item's prices are listed
    for (int i = 0; i < cartTable.getRowCount(); i++) {
        total += Double.parseDouble(cartTable.getValueAt(i, 2).toString()); 
    }
    cartAmount.setText("Total: P " + Double.toString(total));
}

}

remove an item from the cart按钮代码：

 try {
            for (int i = 0; i < cartTable.getRowCount(); i++) {
                total = total - Double.parseDouble(cartTable.getValueAt(i, 2).toString());
            }
            cartAmount.setText("Total: P " + Double.toString(total));
            if (total <= 0.0) {
                total = 0.0;
            }
            {
                int getSelectedRowForDeletion = cartTable.getSelectedRow();
                model2.removeRow(getSelectedRowForDeletion);
                JOptionPane.showMessageDialog(null, "Item removed from cart");
            }
        } catch (NumberFormatException ex) {
            ex.printStackTrace();
        } catch (ArrayIndexOutOfBoundsException ex) {
        }
    }

以下是添加和删除项目时的一些图片：

当未选择任何行时，如何使“删除”按钮不起作用？喜欢要求用户在删除前选择一行吗？还消除了计算负数之和的可能性。谢谢

Answer 1

添加到购物车按钮：

 if (e.getSource() == movebutton) {
        try {
            int index[] = productTable.getSelectedRows();
            Object[] row = new Object[4];

            for (int i = 0; i < index.length; i++) {
                row[0] = model.getValueAt(index[i], 0);
                row[1] = model.getValueAt(index[i], 1);
                row[2] = model.getValueAt(index[i], 2);
                model2.addRow(row);
            }
            DefaultTableModel t = (DefaultTableModel) productTable.getModel();
            int selectedRow = productTable.getSelectedRow();
                {
                    total += Double.parseDouble(t.getValueAt(selectedRow, 2).toString());
                }
                cartAmount.setText("Total: P " + Double.toString(total));
            }catch (ArrayIndexOutOfBoundsException a) {
        }
    }

[删除按钮：

if (e.getSource() == remove) {
        try {
            DefaultTableModel t = (DefaultTableModel) cartTable.getModel();
            int getSelectedRowForDeletion = cartTable.getSelectedRow();
            if (getSelectedRowForDeletion >= 0) {
                int selectedRow = cartTable.getSelectedRow();
                total -= Double.parseDouble(t.getValueAt(selectedRow, 2).toString());
                cartAmount.setText("Total: P " + Double.toString(total));
                model2.removeRow(getSelectedRowForDeletion);
                JOptionPane.showMessageDialog(null, "Item removed from cart!");
            } else {
                JOptionPane.showMessageDialog(null, "Select an item to remove.");
            }
        } catch (ArrayIndexOutOfBoundsException a) {
        }
    }

我在添加值时删除了for循环，因为它将仅添加productTable中的下一项。删除按钮也是如此。