设置监听到的TableModel要求

Question

我试图取决于项目是否被添加或删除我的GUI更新的JTable更新。 JTextField中的总价格应增加或减少，具体取决于删除或添加的项目。我知道我应该使用TableModelListener动态更新它。我也需要将它设置在一个完整的JTextField中，但我不确定如何正确处理它。这是我的代码。

 package classes; 

     import java.awt.*; 
     import java.awt.GridLayout; 
     import java.awt.event.*; 
     import java.sql.*; 
     import java.text.SimpleDateFormat; 
     import java.util.Calendar; 
     import javax.swing.*; 
     import javax.swing.Timer; 
     import javax.swing.border.EmptyBorder; 
     import javax.swing.table.DefaultTableModel; 
     import javax.swing.table.TableModel; 
     import javax.swing.event.*; 

     public class CoffeeTill_GUI extends JFrame { 

      private JPanel contentPane; 
      JLabel orderDescription = new JLabel("Order Description:"); 
      private JTextField totalTF; 
      private double total = 0.0; 
      private double tendered = 0.0; 
      private double change = 0.0; 
      private TableModelListener tableModelListener; 

      // Editing An Order 
      //TableModelListener to listen for changes in the tableModel 
        private void setTableModelListener() { 
         tableModelListener = new TableModelListener() { 

          @Override 
          public void tableChanged(TableModelEvent e) { 
           if (e.getType() == TableModelEvent.UPDATE) { 
            System.out.println("Cell " + e.getFirstRow() + ", " 
              + e.getColumn() + " changed. The new value: " 
              + table.getModel().getValueAt(e.getFirstRow(), 
              e.getColumn())); 
            int row = e.getFirstRow(); 
            int column = e.getColumn(); 
            if (column == 0 || column == 1) 
            { 
             TableModel model = table.getModel(); 
             int quantity = ((Integer) model.getValueAt(row, 0)).intValue(); 
             double price = ((Double) model.getValueAt(row, 1)).doubleValue(); 
             Double value = new Double(quantity * price); 
             model.setValueAt(value, row, 1); 
            } 
           } 
          } 
         }; 
         table.getModel().addTableModelListener(tableModelListener); 
        } 

      // JDBC Driver name and database URL 
      final String JDBC_DRIVER = "com.mysql.jdbc.Driver"; 
      final String DB_URL = "jdbc:mysql://localhost:3306/team_project?useSSL=false"; 
      final String USER_NAME = "root"; 
      final String PASSWORD = "password"; 

      // sql variables 
      Statement statement = null; 
      ResultSet resultSet = null; 

      // Update JTable when JButton is clicked 
      public void updateTable(int prodIn) { 
       try { 
        Class.forName("com.mysql.jdbc.Driver"); 
        Connection conn = (Connection) DriverManager.getConnection(DB_URL, USER_NAME, PASSWORD); 

        Statement stmt = conn.createStatement(); 
        String sqlString = "select ProductID, ProductName, Price from product where ProductID = " + prodIn; 
        stmt.executeQuery(sqlString); 
       } catch (Exception e) { 
        e.printStackTrace(); 
       } 
      } 

      // creating new stock item 
      Stock productPrice = new Stock(); 
      Stock productName = new Stock(); 
      JTable table = new JTable(); 

      JButton delButton = new JButton("DEL"); 
      JButton minusButton = new JButton("-"); 
      JButton plusButton = new JButton("+"); 

      /** 
      * Launch the application. 
      */ 
      public static void main(String[] args) { 
       EventQueue.invokeLater(new Runnable() { 
        public void run() { 
         try { 
          CoffeeTill_GUI frame = new CoffeeTill_GUI(); 
          frame.setExtendedState(JFrame.MAXIMIZED_BOTH); 
          frame.setUndecorated(false); 
          frame.setLocationRelativeTo(null); 
          frame.setVisible(true); 
         } catch (Exception e) { 
          e.printStackTrace(); 
         } 
        } 
       }); 
      } 

      // Connection Object 
      Connection connection = null; 
      private JTextField tenderedTF; 
      private JTextField changeTF; 

      /** 
      * Create the frame. 
      */ 
      public CoffeeTill_GUI() { 
       try { 
        connection = (Connection) DriverManager.getConnection(DB_URL, USER_NAME, PASSWORD); 
       } catch (SQLException e1) { 
        // TODO Auto-generated catch block 
        e1.printStackTrace(); 
       } 
       setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
       setBounds(100, 100, 1200, 686); 
       contentPane = new JPanel(); 
       contentPane.setBorder(new EmptyBorder(5, 5, 5, 5)); 
       setContentPane(contentPane); 
       contentPane.setLayout(null); 

       // COFFEE PANEL - START ----------------------------------------- 
       JTabbedPane tabbedPane = new JTabbedPane(JTabbedPane.TOP); 
       tabbedPane.setBounds(20, 74, 796, 563); 
       contentPane.add(tabbedPane); 

       JPanel panel = new JPanel(); 
       tabbedPane.addTab("Coffee", null, panel, null); 
       panel.setLayout(null); 

       JLabel lblCoffee = new JLabel("Americano"); 
       lblCoffee.setHorizontalAlignment(SwingConstants.CENTER); 
       lblCoffee.setFont(new Font("Tahoma", Font.PLAIN, 30)); 
       lblCoffee.setBounds(10, 45, 154, 45); 
       panel.add(lblCoffee); 

       JLabel label = new JLabel("Cappucino"); 
       label.setHorizontalAlignment(SwingConstants.CENTER); 
       label.setFont(new Font("Tahoma", Font.PLAIN, 30)); 
       label.setBounds(10, 117, 154, 45); 
       panel.add(label); 

       JLabel label_1 = new JLabel("Espresso"); 
       label_1.setHorizontalAlignment(SwingConstants.CENTER); 
       label_1.setFont(new Font("Tahoma", Font.PLAIN, 30)); 
       label_1.setBounds(10, 191, 154, 45); 
       panel.add(label_1); 

       JLabel label_2 = new JLabel("Latte"); 
       label_2.setHorizontalAlignment(SwingConstants.CENTER); 
       label_2.setFont(new Font("Tahoma", Font.PLAIN, 30)); 
       label_2.setBounds(10, 274, 154, 45); 
       panel.add(label_2); 

       JLabel label_3 = new JLabel("Mocha"); 
       label_3.setHorizontalAlignment(SwingConstants.CENTER); 
       label_3.setFont(new Font("Tahoma", Font.PLAIN, 30)); 
       label_3.setBounds(10, 355, 154, 45); 
       panel.add(label_3); 

       JLabel label_4 = new JLabel("Macchiato"); 
       label_4.setHorizontalAlignment(SwingConstants.CENTER); 
       label_4.setFont(new Font("Tahoma", Font.PLAIN, 30)); 
       label_4.setBounds(10, 440, 154, 45); 
       panel.add(label_4); 

       JButton americanoSmall = new JButton("SMALL"); 
       americanoSmall.setBounds(191, 45, 164, 45); 
       panel.add(americanoSmall); 

       JButton americanoMedium = new JButton("MEDIUM"); 
       americanoMedium.setBounds(365, 45, 164, 45); 
       panel.add(americanoMedium); 

       JButton americanoLarge = new JButton("LARGE"); 
       americanoLarge.setBounds(539, 45, 164, 45); 
       panel.add(americanoLarge); 

       JButton cappuchinoSmall = new JButton("SMALL"); 
       cappuchinoSmall.setBounds(191, 117, 164, 45); 
       panel.add(cappuchinoSmall); 

       JButton cappuchinoMedium = new JButton("MEDIUM"); 
       cappuchinoMedium.setBounds(365, 117, 164, 45); 
       panel.add(cappuchinoMedium); 

       JButton cappuchinoLarge = new JButton("LARGE"); 
       cappuchinoLarge.setBounds(539, 117, 164, 45); 
       panel.add(cappuchinoLarge); 

       JButton espressoSmall = new JButton("SMALL"); 
       espressoSmall.setBounds(191, 191, 164, 45); 
       panel.add(espressoSmall); 

       JButton espressoMedium = new JButton("MEDIUM"); 
       espressoMedium.setBounds(365, 191, 164, 45); 
       panel.add(espressoMedium); 

       JButton espressoLarge = new JButton("LARGE"); 
       espressoLarge.setBounds(539, 191, 164, 45); 
       panel.add(espressoLarge); 

       JButton latteSmall = new JButton("SMALL"); 
       latteSmall.setBounds(191, 274, 164, 45); 
       panel.add(latteSmall); 

       JButton latteMedium = new JButton("MEDIUM"); 
       latteMedium.setBounds(365, 274, 164, 45); 
       panel.add(latteMedium); 

       JButton latteLarge = new JButton("LARGE"); 
       latteLarge.setBounds(539, 274, 164, 45); 
       panel.add(latteLarge); 

       JButton mochaSmall = new JButton("SMALL"); 
       mochaSmall.setBounds(191, 355, 164, 45); 
       panel.add(mochaSmall); 

       JButton mochaMedium = new JButton("MEDIUM"); 
       mochaMedium.setBounds(365, 355, 164, 45); 
       panel.add(mochaMedium); 

       JButton mochaLarge = new JButton("LARGE"); 
       mochaLarge.setBounds(539, 355, 164, 45); 
       panel.add(mochaLarge); 

       JButton macchiatoSmall = new JButton("SMALL"); 
       macchiatoSmall.setBounds(191, 440, 164, 45); 
       panel.add(macchiatoSmall); 

       JButton macchiatoMedium = new JButton("MEDIUM"); 
       macchiatoMedium.setBounds(365, 440, 164, 45); 
       panel.add(macchiatoMedium); 

       JButton macchiatoLarge = new JButton("LARGE"); 
       macchiatoLarge.setBounds(539, 440, 164, 45); 
       panel.add(macchiatoLarge); 
       // COFFEE PANEL - END ----------------------------------------- 

       // COLD DRINKS PANELS - START ----------------------------------------- 
       JPanel panel_1 = new JPanel(); 
       tabbedPane.addTab("Cold Drinks", null, panel_1, null); 
       panel_1.setLayout(new GridLayout(2, 2)); 
       ImageIcon waterIcon, cokeIcon, spriteIcon, fantaIcon; 
       JButton waterButton, cokeButton, spriteButton, fantaButton; 

       panel_1.add(waterButton = new JButton(waterIcon = new ImageIcon("image/water.jpg"))); 
       panel_1.add(cokeButton = new JButton(cokeIcon = new ImageIcon("image/coke.jpg"))); 
       panel_1.add(spriteButton = new JButton(spriteIcon = new ImageIcon("image/sprite.jpg"))); 
       panel_1.add(fantaButton = new JButton(fantaIcon = new ImageIcon("image/fanta.jpg"))); 
       // COLD DRINKS PANEL - END ----------------------------------------- 

       // SANDWICHES - START ----------------------------------------- 
       JButton hamAndCheese, bltButton, tunaAndSweetcorn, chickenAndHam, hamAndCheesePanini; 

       JPanel panel_2 = new JPanel(); 
       tabbedPane.addTab("Sandwiches", null, panel_2, null); 
       panel_2.setLayout(new GridLayout(5, 1)); 
       panel_2.add(hamAndCheese = new JButton("Ham & Cheese")); 
       panel_2.add(bltButton = new JButton("BLT")); 
       panel_2.add(tunaAndSweetcorn = new JButton("Tuna & Sweetcorn")); 
       panel_2.add(chickenAndHam = new JButton("Chicken & Ham")); 
       panel_2.add(hamAndCheesePanini = new JButton("Ham & Cheese Panini")); 
       // SANDWICHES - END ----------------------------------------- 

       // PASTRIES - START ----------------------------------------- 
       JButton danishPastryJbt, muffinJbt, cinnamonRoleJbt, profiteroleJbt, eclairJbt, croissantJbt; 
       JPanel panel_3 = new JPanel(); 
       panel_3.setLayout(new GridLayout(6, 1)); 
       tabbedPane.addTab("Pastries", null, panel_3, null); 
       panel_3.add(danishPastryJbt = new JButton("Danish Pastry")); 
       panel_3.add(muffinJbt = new JButton("Muffin")); 
       panel_3.add(cinnamonRoleJbt = new JButton("Cinnamon Role")); 
       panel_3.add(profiteroleJbt = new JButton("Profiterole")); 
       panel_3.add(eclairJbt = new JButton("Eclair")); 
       panel_3.add(croissantJbt = new JButton("Croissant")); 

       orderDescription.setFont(new Font("Tahoma", Font.PLAIN, 20)); 
       orderDescription.setBounds(845, 55, 214, 33); 
       contentPane.add(orderDescription); 
       // ORDER - END ----------------------------------------- 

       // HEADING - START ----------------------------------------- 
       JLabel lblUserEmployee = new JLabel("User: Employee1"); 
       lblUserEmployee.setFont(new Font("Tahoma", Font.PLAIN, 20)); 
       lblUserEmployee.setBounds(20, 11, 204, 33); 
       contentPane.add(lblUserEmployee); 

       JLabel lblJavaHouseCoffee = new JLabel("Java House Coffee"); 
       lblJavaHouseCoffee.setHorizontalAlignment(SwingConstants.CENTER); 
       lblJavaHouseCoffee.setFont(new Font("Tahoma", Font.PLAIN, 40)); 
       lblJavaHouseCoffee.setBounds(333, 11, 480, 60); 
       contentPane.add(lblJavaHouseCoffee); 

       // Setting the Time on the GUI 
       JLabel lblTime = new JLabel(""); 
       String timeStamp = new SimpleDateFormat("dd:MM:yyyy HH:mm:ss").format(Calendar.getInstance().getTime()); 
       lblTime.setFont(new Font("Tahoma", Font.PLAIN, 18)); 
       lblTime.setBounds(650, 0, 120, 30); 
       lblTime.setText(timeStamp + ""); 
       lblTime.setVisible(true); 
       int delay = 1000; // milliseconds 
       ActionListener taskPerformer = new ActionListener() { 
        public void actionPerformed(ActionEvent evt) { 
         String date = new java.text.SimpleDateFormat("HH:mm:ss") 
           .format(new java.util.Date(System.currentTimeMillis())); 
         lblTime.setText("" + Calendar.getInstance().getTime()); 
        } 
       }; 
       new Timer(delay, taskPerformer).start(); 

       lblTime.setHorizontalAlignment(SwingConstants.CENTER); 
       lblTime.setFont(new Font("Tahoma", Font.PLAIN, 20)); 
       lblTime.setBounds(914, 11, 244, 45); 
       contentPane.add(lblTime); 

       // add header of the table 
       String columns[] = new String[] { "Product Name", "Price" }; 
       DefaultTableModel dtm = new DefaultTableModel(columns, 0); 
       dtm.setColumnIdentifiers(columns); 
       table.setModel(dtm); 

       // round the prices values pulled from DB to 2 Decimal Places 
       table.getColumnModel().getColumn(1).setCellRenderer(new DecimalFormatRenderer()); 
       getContentPane().add(new JScrollPane(table)); 
       table.setFont(new Font("Serif", Font.PLAIN, 18)); 

       // add header of the table 
       JScrollPane scrollPaneTable = new JScrollPane(table); 
       scrollPaneTable.setBounds(845, 94, 329, 241); 
       contentPane.add(scrollPaneTable); 

       JPanel panel_5 = new JPanel(); 
       scrollPaneTable.setColumnHeaderView(panel_5); 
       panel_5.setLayout(new BorderLayout()); 

       JLabel totalJLabel = new JLabel("Total €"); 
       totalJLabel.setFont(new Font("Tahoma", Font.PLAIN, 20)); 
       totalJLabel.setBounds(899, 400, 63, 45); 
       contentPane.add(totalJLabel); 

       totalTF = new JTextField(); 
       totalTF.setFont(new Font("Tahoma", Font.PLAIN, 20)); 
       totalTF.setBounds(970, 400, 204, 45); 
       contentPane.add(totalTF); 
       totalTF.setColumns(10); 
       totalTF.setEditable(false); 
       delButton.setBounds(845, 346, 96, 45); 
       contentPane.add(delButton); 

       delButton.setFont(new Font("Tahoma", Font.PLAIN, 15)); 
       minusButton.setBounds(963, 346, 96, 45); 
       contentPane.add(minusButton); 

       minusButton.setFont(new Font("Tahoma", Font.PLAIN, 15)); 
       plusButton.setBounds(1083, 346, 87, 45); 
       contentPane.add(plusButton); 

       plusButton.setFont(new Font("Tahoma", Font.PLAIN, 15)); 

       JLabel tenderedJLabel = new JLabel("Tendered €"); 
       tenderedJLabel.setFont(new Font("Tahoma", Font.PLAIN, 20)); 
       tenderedJLabel.setBounds(858, 456, 102, 45); 
       contentPane.add(tenderedJLabel); 

       tenderedTF = new JTextField(); 
       tenderedTF.setFont(new Font("Tahoma", Font.PLAIN, 20)); 
       tenderedTF.setBounds(972, 456, 202, 45); 
       contentPane.add(tenderedTF); 
       tenderedTF.setColumns(10); 

       JLabel changeJlabel = new JLabel("Change €"); 
       changeJlabel.setFont(new Font("Tahoma", Font.PLAIN, 20)); 
       changeJlabel.setBounds(878, 521, 84, 37); 
       contentPane.add(changeJlabel); 

       changeTF = new JTextField(); 
       changeTF.setFont(new Font("Tahoma", Font.PLAIN, 20)); 
       changeTF.setEditable(false); 
       changeTF.setBounds(972, 512, 202, 46); 
       contentPane.add(changeTF); 
       changeTF.setColumns(10); 

       // Delete row from JTable when clicked by user 
       delButton.addActionListener(new ActionListener() { 
        public void actionPerformed(ActionEvent e) { 
         int viewIndex = table.getSelectedRow(); 
         if (viewIndex != -1) { 
          // converts the row index in the view to the appropriate 
          // index in the model 
          int modelIndex = table.convertRowIndexToModel(viewIndex); 
          DefaultTableModel model = (DefaultTableModel) table.getModel(); 
          model.removeRow(modelIndex); 
         } 
        } 
       }); 
       table.getTableHeader().setReorderingAllowed(false); 

       // HEADING - END ----------------------------------------- 

       // Small Americano ActionListener 
       americanoSmall.addActionListener(new ActionListener() { 
        public void actionPerformed(ActionEvent e) { 
         try { 
          String query = "select ProductName, Price from product where ProductID = 24"; 
          java.sql.PreparedStatement pst = connection.prepareStatement(query); 
          ResultSet rs = pst.executeQuery(); 

          // Loop through the ResultSet and transfer in the Model 
          java.sql.ResultSetMetaData rsmd = rs.getMetaData(); 
          int colNo = rsmd.getColumnCount(); 
          while (rs.next()) { 
           Object[] objects = new Object[colNo]; 

           for (int i = 0; i < colNo; i++) { 
            objects[i] = rs.getObject(i + 1); 
           } 
           DefaultTableModel model = (DefaultTableModel) table.getModel(); 
           model.addRow(objects); 
           Stock s = new Stock(); 
           // deduct stock from db from 
           // s1.deductStock(24); 
           total = total + s.getItemPrice(24); 
           totalTF.setText(String.valueOf(total)); 
           totalTF.setText(String.format("%.2f", total)); 

          } 
          TableModel model = (DefaultTableModel) table.getModel(); 
          table.setModel(model); 
         } catch (Exception e1) { 
          e1.printStackTrace(); 
         } 
        } 
       }); 

       americanoMedium.addActionListener(new ActionListener() { 
        public void actionPerformed(ActionEvent e) { 
         try { 
          String query = "select ProductName, Price from product where ProductID = 25"; 
          java.sql.PreparedStatement pst = connection.prepareStatement(query); 
          ResultSet rs = pst.executeQuery(); 

          // Loop through the ResultSet and transfer in the Model 
          java.sql.ResultSetMetaData rsmd = rs.getMetaData(); 
          int colNo = rsmd.getColumnCount(); 
          while (rs.next()) { 
           Object[] objects = new Object[colNo]; 

           for (int i = 0; i < colNo; i++) { 
            objects[i] = rs.getObject(i + 1); 
           } 
           DefaultTableModel model = (DefaultTableModel) table.getModel(); 
           model.addRow(objects); 
           Stock s = new Stock(); 
           // deduct stock from db from 
           // s1.deductStock(24); 
           total = total + s.getItemPrice(25); 
           totalTF.setText(String.valueOf(total)); 
           totalTF.setText(String.format("%.2f", total)); 
          } 
          TableModel model = (DefaultTableModel) table.getModel(); 
          table.setModel(model); 

         } catch (Exception e2) { 
          e2.printStackTrace(); 
         } 
        } 
       }); 

       americanoLarge.addActionListener(new ActionListener() { 
        public void actionPerformed(ActionEvent e) { 
         try { 
          String query = "select ProductName, Price from product where ProductID = 26"; 
          java.sql.PreparedStatement pst = connection.prepareStatement(query); 
          ResultSet rs = pst.executeQuery(); 

          // Loop through the ResultSet and transfer in the Model 
          java.sql.ResultSetMetaData rsmd = rs.getMetaData(); 
          int colNo = rsmd.getColumnCount(); 
          while (rs.next()) { 
           Object[] objects = new Object[colNo]; 
           for (int i = 0; i < colNo; i++) { 
            objects[i] = rs.getObject(i + 1); 
           } 
           DefaultTableModel model = (DefaultTableModel) table.getModel(); 
           model.addRow(objects); 
           Stock s = new Stock(); 
           // deduct stock from db from 
           // s1.deductStock(24); 
           total = total + s.getItemPrice(26); 
           totalTF.setText(String.valueOf(total)); 
           totalTF.setText(String.format("%.2f", total)); 
          } 
          TableModel model = (DefaultTableModel) table.getModel(); 
          table.setModel(model); 

         } catch (Exception e2) { 
          e2.printStackTrace(); 
         } 
        } 
       }); 

       cappuchinoSmall.addActionListener(new ActionListener() { 
        public void actionPerformed(ActionEvent e) { 
         try { 
          String query = "select ProductName, Price from product where ProductID = 30"; 
          java.sql.PreparedStatement pst = connection.prepareStatement(query); 
          ResultSet rs = pst.executeQuery(); 

          // Loop through the ResultSet and transfer in the Model 
          java.sql.ResultSetMetaData rsmd = rs.getMetaData(); 
          int colNo = rsmd.getColumnCount(); 
          while (rs.next()) { 
           Object[] objects = new Object[colNo]; 

           for (int i = 0; i < colNo; i++) { 
            objects[i] = rs.getObject(i + 1); 
           } 
           DefaultTableModel model = (DefaultTableModel) table.getModel(); 
           model.addRow(objects); 
           Stock s = new Stock(); 
           // deduct stock from db from 
           // s1.deductStock(24); 
           total = total + s.getItemPrice(30); 
           totalTF.setText(String.valueOf(total)); 
           totalTF.setText(String.format("%.2f", total)); 
          } 
          TableModel model = (DefaultTableModel) table.getModel(); 
          table.setModel(model); 
         } catch (Exception e2) { 
          e2.printStackTrace(); 
         } 
        } 
       }); 

       cappuchinoMedium.addActionListener(new ActionListener() { 
        public void actionPerformed(ActionEvent e) { 
         try { 
          String query = "select ProductName, Price from product where ProductID = 31"; 
          java.sql.PreparedStatement pst = connection.prepareStatement(query); 
          ResultSet rs = pst.executeQuery(); 

          // Loop through the ResultSet and transfer in the Model 
          java.sql.ResultSetMetaData rsmd = rs.getMetaData(); 
          int colNo = rsmd.getColumnCount(); 
          while (rs.next()) { 
           Object[] objects = new Object[colNo]; 

           for (int i = 0; i < colNo; i++) { 
            objects[i] = rs.getObject(i + 1); 
           } 
           DefaultTableModel model = (DefaultTableModel) table.getModel(); 
           model.addRow(objects); 
           Stock s = new Stock(); 
           // deduct stock from db from 
           // s1.deductStock(24); 
           total = total + s.getItemPrice(31); 
           totalTF.setText(String.valueOf(total)); 
           totalTF.setText(String.format("%.2f", total)); 
          } 
          TableModel model = (DefaultTableModel) table.getModel(); 
          table.setModel(model); 
         } catch (Exception e2) { 
          e2.printStackTrace(); 
         } 
        } 
       }); 

       cappuchinoLarge.addActionListener(new ActionListener() { 
        public void actionPerformed(ActionEvent e) { 
         try { 
          String query = "select ProductName, Price from product where ProductID = 32"; 
          java.sql.PreparedStatement pst = connection.prepareStatement(query); 
          ResultSet rs = pst.executeQuery(); 

          // Loop through the ResultSet and transfer in the Model 
          java.sql.ResultSetMetaData rsmd = rs.getMetaData(); 
          int colNo = rsmd.getColumnCount(); 
          while (rs.next()) { 
           Object[] objects = new Object[colNo]; 

           for (int i = 0; i < colNo; i++) { 
            objects[i] = rs.getObject(i + 1); 
           } 
           DefaultTableModel model = (DefaultTableModel) table.getModel(); 
           model.addRow(objects); 
           Stock s = new Stock(); 
           // deduct stock from db from 
           // s1.deductStock(24); 
           total = total + s.getItemPrice(32); 
           totalTF.setText(String.valueOf(total)); 
           totalTF.setText(String.format("%.2f", total)); 

          } 
          TableModel model = (DefaultTableModel) table.getModel(); 
          table.setModel(model); 
         } catch (Exception e2) { 
          e2.printStackTrace(); 
         } 
        } 
       }); 

       JButton payButton = new JButton("Pay"); 
       payButton.setBounds(970, 569, 209, 51); 
       contentPane.add(payButton);; 

}// end class 

Answer 1

所以这是概念的非常基本的证明。

它的作用是什么，它保持其添加/删除/更新的值的内部“代理” /“缓存”。通过这种方式，它可以使用事件信息来简单地更新计数，而不必重新迭代模型，这可能很耗时。

当你创建一个新的模式，你应该重视的听众给它之前，填充它，这会给听者有机会被通知的新行和更新其内部状态。

import java.awt.BorderLayout; 
import java.awt.event.ActionEvent; 
import java.awt.event.ActionListener; 
import java.text.NumberFormat; 
import java.util.ArrayList; 
import java.util.Collections; 
import java.util.HashMap; 
import java.util.List; 
import java.util.Map; 
import javax.swing.JButton; 
import javax.swing.JFrame; 
import javax.swing.JPanel; 
import javax.swing.JScrollPane; 
import javax.swing.JTable; 
import javax.swing.JTextField; 
import javax.swing.SwingUtilities; 
import javax.swing.event.TableModelEvent; 
import javax.swing.event.TableModelListener; 
import javax.swing.table.DefaultTableModel; 

public class Test { 

    public static void main(String[] args) { 
     new Test(); 
    } 

    public Test() { 
     SwingUtilities.invokeLater(new Runnable() { 
      @Override 
      public void run() { 
       JFrame frame = new JFrame(); 
       frame.add(new TestPane()); 
       frame.pack(); 
       frame.setLocationRelativeTo(null); 
       frame.setVisible(true); 
      } 
     }); 
    } 

    public class TestPane extends JPanel { 

     private DefaultTableModel model; 
     private JTextField tallyField; 
     private double tally; 

     public TestPane() { 
      setLayout(new BorderLayout()); 
      tallyField = new JTextField(10); 
      // When loading data, update this value to represent the total 
      // of the data that was loaded 
      tally = 0; 
      model = new DefaultTableModel(new Object[]{"Quanity", "Amount"}, 0); 
      model.addTableModelListener(new TableModelListener() { 

       private Map<Integer, Double> proxy = new HashMap<Integer, Double>(); 
       private NumberFormat nf = NumberFormat.getCurrencyInstance(); 

       @Override 
       public void tableChanged(TableModelEvent e) { 
        int firstRow = e.getFirstRow(); 
        int lastRow = e.getLastRow(); 
        double sum = 0; 
        for (int row = Math.min(firstRow, lastRow); row <= Math.max(firstRow, lastRow); row++) { 
         switch (e.getType()) { 
          case TableModelEvent.DELETE: 
           sum -= delete(row); 
           break; 
          case TableModelEvent.INSERT: 
           sum += add(row); 
           break; 
          case TableModelEvent.UPDATE: 
           sum -= delete(row); 
           sum += add(row); 
           break; 
          default: 
           break; 
         } 
        } 
        tally += sum; 
        tallyField.setText(nf.format(tally)); 
       } 

       protected double delete(int row) { 
        double sum = 0; 
        if (proxy.containsKey(row)) { 
         sum = proxy.get(row); 
        } 
        proxy.remove(row); 
        return sum; 
       } 

       protected double add(int row) { 
        int qty = 0; 
        // I hope your model is better setup then mine 
        if (model.getValueAt(row, 0) instanceof String) { 
         qty = Integer.parseInt((String) model.getValueAt(row, 0)); 
        } else if (model.getValueAt(row, 0) instanceof Integer) { 
         qty = (Integer) model.getValueAt(row, 0); 
        } 
        double amount = (Double) model.getValueAt(row, 1); 
        double rowTotal = qty * amount; 
        proxy.put(row, rowTotal); 
        return rowTotal; 
       } 
      }); 

      JTable table = new JTable(model); 
      add(new JScrollPane(table)); 

      JButton add = new JButton("Add"); 
      JButton delete = new JButton("Delete"); 

      add.addActionListener(new ActionListener() { 
       @Override 
       public void actionPerformed(ActionEvent e) { 
        double amount = 1.0; //Math.random() * 1000.0; 
        model.addRow(new Object[]{1, amount}); 
       } 
      }); 
      delete.addActionListener(new ActionListener() { 
       @Override 
       public void actionPerformed(ActionEvent e) { 
        int[] rows = table.getSelectedRows(); 
        List<Integer> selection = new ArrayList<>(rows.length); 
        for (int row : rows) { 
         selection.add(row); 
        } 
        Collections.sort(selection); 
        Collections.reverse(selection); 
        for (int row : selection) { 
         model.removeRow(row); 
        } 
       } 
      }); 

      JPanel footer = new JPanel(new BorderLayout()); 
      JPanel buttons = new JPanel(); 
      buttons.add(add); 
      buttons.add(delete); 

      footer.add(tallyField); 
      footer.add(buttons, BorderLayout.SOUTH); 

      add(footer, BorderLayout.SOUTH); 

     } 

    } 
} 

为什么我们需要缓存？因为当一行被删除时，你不能再确定它的值。

如果我在实际应用中这样做，我会做一个简单的类，它实现TableModelListener但提供一个getter检索tally（所以tally变得封装到类），并使用观察者模式生成通知当tally被改变时。

这意味着，当你加载数据，可以独立更新模型和“理货监控”。当你需要时，更新屏幕上的必填字段。

这可能会变得非常复杂，很快。它做了一件simular产生自动统计系统为独立清点模型的行和列，因此系统未从已知的行/列是负责清点