java - JTable 未在 ActionEvent 中显示

Question

我打算在我在本类(class)中创建的 JTable 中显示学生成绩。我的意图是在加载表单时有一个空表，在输入一些参数时有一个空表，查询数据库并将结果显示在 JTable 中。空表正在显示，但在单击按钮时没有任何反应。也不异常(exception)。它只是保持为空。这是我的代码...(部分)

public class ClassExamResults extends JInternalFrame implements ActionListener {

private JPanel jpCer = new JPanel();
private DefaultTableModel dtmCustomer;
private JTable tbCustomer;
private JScrollPane jspTable;
static Vector<Vector<String>> data = new Vector<Vector<String>>();

ClassExamResults() {
    super("Class Exam Results", false, true, false, true);
    setSize(1350, 620);
    jpCer.setBounds(10, 0, 500, 150);
    jpCer.setLayout(null);
    jpCer.setBackground(Color.LIGHT_GRAY);

    //Define table
    tbCustomer = makeTable();
    jspTable = new JScrollPane(tbCustomer);
    jspTable.setBounds(170, 20, 1150, 550);



    jpCer.add(jspTable);


    getContentPane().add(jpCer);
    setVisible(true);

}

private JTable makeTable() {
    //String Type Array use to Give Table Column Names.
    Vector<String> headers = new Vector<String>();

    headers.add("ADMIS. NO.");
    headers.add("NAME");
    headers.add("EXAM");
    headers.add("MATHS");
    headers.add("ENG.");
    headers.add("KISWA.");
    headers.add("PHYC.");
    headers.add("CHEM");
    headers.add("BIO");
    headers.add("HISTO.");
    headers.add("GEOG.");
    headers.add("CRE");
    headers.add("COMP.");
    headers.add("HOME SC.");
    headers.add("BUSIN");
    headers.add("AGRIC.");
    headers.add("TOTAL");
    headers.add("AVERAGE");
    headers.add("POS.");



    dtmCustomer = new DefaultTableModel(data, headers);
    tbCustomer = new JTable(dtmCustomer) {
        public boolean isCellEditable(int iRow, int iCol) {
            return false;   //Disable All Columns of Table.
        }
    };
    tbCustomer.setRowHeight(25);
    tbCustomer.setBackground(new java.awt.Color(89, 151, 207));
    tbCustomer.setForeground(Color.BLACK);
    tbCustomer.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);


    return tbCustomer;
}



public void actionPerformed(ActionEvent ae) {
    Object obj = ae.getSource();
    if (obj == btnFind) {
        if (level.equalsIgnoreCase("SELECT")) {
            JOptionPane.showMessageDialog(this, "Please Select Exam Level",
                    "Error", JOptionPane.ERROR_MESSAGE);
            cboLevel.requestFocus();
        } else if (year.equalsIgnoreCase("SELECT")) {
            JOptionPane.showMessageDialog(this, "Please Select Exam Academic year",
                    "Error", JOptionPane.ERROR_MESSAGE);
            cboYear.requestFocus();
        } else {
            Connection conn = null;
            Vector<String> headers = new Vector<String>();
            try {
                Class.forName("oracle.jdbc.driver.OracleDriver");
                conn = DriverManager.getConnection("jdbc:oracle:thin:@localhost:1521:XE", "USERNAME", "PASSWORD");
                Statement st = conn.createStatement();
                String results = "select stu_number as ADMISSION_NUMBER, "
                        + " max(stu_name) STUDENT_NAME, "
                        + "ex_name as EXAM_NAME, "
                        + "max(case when ex_subject = 'MATHEMATICS' then stu_score else 0 end) as MATHEMATICS, "
                        + " max(case when ex_subject = 'ENGLISH' then stu_score else 0 end) as ENGLISH, "
                        + " max(case when ex_subject = 'KISWAHILI' then stu_score else 0 end) as KISWAHILI, "
                        + " max(case when ex_subject = 'PHYSICS' then stu_score else 0 end) as PHYSICS, "
                        + "  max(case when ex_subject = 'CHEMISTRY' then stu_score else 0 end) as CHEMISTRY, "
                        + " max(case when ex_subject = 'BIOLOGY' then stu_score else 0 end) as BIOLOGY, "
                        + "max(case when ex_subject = 'HISTORY' then stu_score else 0 end) as HISTORY, "
                        + " max(case when ex_subject = 'GEOGRAPHY' then stu_score else 0 end) as GEOGRAPHY, "
                        + " max(case when ex_subject = 'CRE' then stu_score else 0 end) as CRE, "
                        + " max(case when ex_subject = 'COMPUTER' then stu_score else 0 end) as COMPUTER, "
                        + " max(case when ex_subject = 'HOME SCIENCE' then stu_score else 0 end) as HOME_SCIENCE, "
                        + "  max(case when ex_subject = 'BUSINESS' then stu_score else 0 end) as BUSINESS, "
                        + "  max(case when ex_subject = 'AGRICULTURE' then stu_score else 0 end) as AGRICULTURE, "
                        + " sum(stu_score) as TOTAL_MARKS, "
                        + "  sum(stu_score)/count(stu_score) as AVERAGE, "
                        + " rank () over (order by sum(stu_score)desc)  as POSITION  "
                        + "from EXAMS_MASTER_REGISTER "
                        + "where stu_level = '" + level + "' and "
                        + " stu_stream = '" + stream + "' and "
                        + " ex_semester = '" + semester + "' and "
                        + " ex_name = '" + exam + "' and "
                        + "  academic_year = '" + year + "' "
                        + "group by stu_number, ex_name "
                        + "order by sum(stu_score) desc";
                ResultSet rs = st.executeQuery(results);
                while (rs.next()) {
                    Vector<String> d = new Vector<String>();


                    d.add(rs.getString("ADMISSION_NUMBER"));
                    d.add(rs.getString("STUDENT_NAME"));
                    d.add(rs.getString("EXAM_NAME"));
                    d.add(rs.getString("MATHEMATICS"));
                    d.add(rs.getString("ENGLISH"));
                    d.add(rs.getString("KISWAHILI"));
                    d.add(rs.getString("PHYSICS"));
                    d.add(rs.getString("CHEMISTRY"));
                    d.add(rs.getString("BIOLOGY"));
                    d.add(rs.getString("HISTORY"));
                    d.add(rs.getString("GEOGRAPHY"));
                    d.add(rs.getString("CRE"));
                    d.add(rs.getString("COMPUTER"));
                    d.add(rs.getString("HOME_SCIENCE"));
                    d.add(rs.getString("BUSINESS"));
                    d.add(rs.getString("AGRICULTURE"));
                    System.out.println(rs.getString("STUDENT_NAME"));



                    data.add(d);

                }


            } catch (Exception db) {
                JOptionPane.showMessageDialog(this, db,
                        "Error", JOptionPane.ERROR_MESSAGE);
            }

        }
    }
}
}

我知道查询执行是从以下时间开始的； System.out.println(rs.getString("STUDENT_NAME"));返回正确的值。我还尝试从蟾蜍运行查询，它显示了正确的结果。我的错误在哪里？

Answer 1

1. 直接往DefaultTableModel dtmCustomer;里放一条新的Records，DefaultTableModel不知道你往底层的Vector of Vector<里填数据，或者你必须调用 DefaultTableModel#setDataVector

2. 您忘记重置 TableModel#setDataVector(null)在任何进一步的步骤之前，在这种情况下，您将在 JTable

的末尾添加一个新行

3. JDBC 从 Event Dispatch Thread 调用，然后 Swing GUI 将被卡住直到 Resultset 结束，使用一些 Workers Thread , Runnable#Thread 或 SwingWorker for JDBC

编辑

• against to reinvent the wheel by @camickr