向 "价格"& "数量 "列单元格添加数据时，更新JTable中的 "金额 "列单元格。

Question

我创建了一个有五列的JTable，其中名称、单位、价格、数量&amp；金额是列名。Name, Unit, Price, Quantity & Amount是列名，使用JText Fields将数据填入表中。点击 "ADD "按钮后工作正常，我写了一段代码，用 "Price "列的单元格值乘以 "Quantity "列的单元格值得到 "Amount"。程序运行，但计算没有发生。帮助我解决这个问题是非常感激。先谢谢你了。

查看-01

public class UnitTable2 extends JFrame implements TableModelListener {

private JFrame frame;
private JTable table;
private JTextField txtName;
private JTextField txtUImp;
private JTextField txtPImp;
private JTextField txtUMetric;
private JTextField txtPMetric;
private JTextField txtQty;
private JComboBox<String> cmbUType;

/**
 * Launch the application.
 */
public static void main(String[] args) {
    EventQueue.invokeLater(new Runnable() {
        public void run() {
            try {
                UnitTable2 window = new UnitTable2();
                window.frame.setVisible(true);
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    });
}

/**
 * Create the application.
 */
public UnitTable2() {
    initialize();
}

/**
 * Initialize the contents of the frame.
 */
private void initialize() {
    frame = new JFrame();
    frame.setBounds(100, 100, 649, 288);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.getContentPane().setLayout(null);

    JScrollPane scrollPane = new JScrollPane();
    scrollPane.setBounds(10, 10, 526, 181);
    frame.getContentPane().add(scrollPane);

    table = new JTable();
    Object[] columns = { "Name", "Unit", "Price", "Quantity", "Amount" };
    DefaultTableModel model = new DefaultTableModel();
    scrollPane.setViewportView(table);
    model.setColumnIdentifiers(columns);
    table.setModel(model);

    model.addTableModelListener(this);

    JLabel lblName = new JLabel("Name");
    lblName.setBounds(10, 201, 96, 13);
    frame.getContentPane().add(lblName);

    txtName = new JTextField();
    txtName.setBounds(10, 224, 96, 19);
    frame.getContentPane().add(txtName);
    txtName.setColumns(10);

    JLabel lblUImp = new JLabel("Unit Imperial");
    lblUImp.setBounds(121, 201, 91, 13);
    frame.getContentPane().add(lblUImp);

    txtUImp = new JTextField();
    txtUImp.setBounds(116, 224, 96, 19);
    frame.getContentPane().add(txtUImp);
    txtUImp.setColumns(10);

    JLabel lblPImp = new JLabel("Price Imperial");
    lblPImp.setBounds(222, 201, 96, 13);
    frame.getContentPane().add(lblPImp);

    txtPImp = new JTextField();
    txtPImp.setBounds(222, 224, 96, 19);
    frame.getContentPane().add(txtPImp);
    txtPImp.setColumns(10);

    JLabel lblUMetric = new JLabel("Unit Metric");
    lblUMetric.setBounds(330, 201, 94, 13);
    frame.getContentPane().add(lblUMetric);

    txtUMetric = new JTextField();
    txtUMetric.setBounds(330, 224, 96, 19);
    frame.getContentPane().add(txtUMetric);
    txtUMetric.setColumns(10);

    JLabel lblPMetric = new JLabel("Price Metric");
    lblPMetric.setBounds(434, 201, 102, 13);
    frame.getContentPane().add(lblPMetric);

    txtPMetric = new JTextField();
    txtPMetric.setBounds(434, 224, 96, 19);
    frame.getContentPane().add(txtPMetric);
    txtPMetric.setColumns(10);

    JLabel lblQty = new JLabel("Quantity");
    lblQty.setBounds(540, 201, 120, 13);
    frame.getContentPane().add(lblQty);

    txtQty = new JTextField();
    txtQty.setBounds(540, 224, 96, 19);
    frame.getContentPane().add(txtQty);
    txtQty.setColumns(10);

    JButton btnAdd = new JButton("ADD");
    Object[] row = new Object[4];
    btnAdd.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {

            String type = (String) cmbUType.getSelectedItem();
            if (type.equals("Imperial")) {
                row[0] = txtName.getText();
                row[1] = txtUImp.getText();
                row[2] = Double.parseDouble(txtPImp.getText());
                row[3] = Double.parseDouble(txtQty.getText());
            } else {
                row[0] = txtName.getText();
                row[1] = txtUMetric.getText();
                row[2] = Double.parseDouble(txtPMetric.getText());
                row[3] = Double.parseDouble(txtQty.getText());
            }

            model.addRow(row);

        }
    });

    btnAdd.setBounds(546, 45, 85, 21);
    frame.getContentPane().add(btnAdd);

    cmbUType = new JComboBox<>();
    cmbUType.setModel(new DefaultComboBoxModel<String>(new String[] { "Imperial", "Metric" }));
    cmbUType.setBounds(546, 8, 85, 21);
    frame.getContentPane().add(cmbUType);

    JButton btnDelete = new JButton("DELETE");
    btnDelete.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {

            int i = table.getSelectedRow();
            if (i >= 0) {
                model.removeRow(i);
            } else {
                JOptionPane.showMessageDialog(null, "Please Select Item to Delete");

            }

        }
    });
    btnDelete.setBounds(546, 76, 85, 21);
    frame.getContentPane().add(btnDelete);

}

// price multiply with quantity and set to amount
public void tableChanged(TableModelEvent e) {
    if (e.getType() == TableModelEvent.UPDATE) {
        int row = e.getFirstRow();
        int column = e.getColumn();

        if (column == 2 || column == 3) {
            TableModel model = table.getModel();
            double price = ((Double) model.getValueAt(row, 2)).doubleValue();
            double quantity = ((Double) model.getValueAt(row, 3)).doubleValue();
            Double value = (price * quantity);
            model.setValueAt(value, row, 4);

        }
    }

}

}

Answer 1

事实上，计算 是否 发生。你看不到更新，因为会抛出一个异常--因为你正试图从TableModel中获取一个Double，而这个Double包含了Strings。当你修改你的tableChanged模型值提取为时，它将开始工作。

double price = Double.parseDouble(model.getValueAt(row, 2).toString());
double quantity = Double.parseDouble(model.getValueAt(row, 3).toString());

但作为一个目标，这可能应该在一个单独的方法中完成，如果值是空的，或者包含双倍值以外的其他内容，则需要验证。