GUI的问题

Question

写了段代码，编译通过，运行出错说空指针，找了2天了都没有找到这个空指针
下面是错误提示
---------- java ----------
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at StudentContentPanel.<init>(StudentFrame.java:79)
at StudentFrame.<init>(StudentFrame.java:29)
at MainButtonPanel$MakeStudentFrameAction.actionPerformed(MainFrame.java:148)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1995)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2318)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:387)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:242)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:236)
at java.awt.AWTEventMulticaster.mouseReleased(AWTEventMulticaster.java:272)
at java.awt.Component.processMouseEvent(Component.java:6038)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3265)
at java.awt.Component.processEvent(Component.java:5803)
at java.awt.Container.processEvent(Container.java:2058)
at java.awt.Component.dispatchEventImpl(Component.java:4410)
at java.awt.Container.dispatchEventImpl(Container.java:2116)
at java.awt.Component.dispatchEvent(Component.java:4240)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4322)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:3986)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:3916)
at java.awt.Container.dispatchEventImpl(Container.java:2102)
at java.awt.Window.dispatchEventImpl(Window.java:2429)
at java.awt.Component.dispatchEvent(Component.java:4240)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:599)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:273)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:183)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:173)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:168)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:160)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:121)

Answer 1

代码如下  import java.util.Vector;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
 /*
 * 这是课程信息维护的主界面，包括添加、删除功能。
 * 如果点击添加按钮，会弹出一个新的界面，让用户输入相应的信息。
 * 如果点击删除，会弹出确认对话框，让用户确认删除的信息。
 */
public class StudentFrame extends JFrame
{

private static final int WIDTH = 400;
private static final int HEIGHT = 300;
private JComboBox studentIdCombox = new JComboBox();
    private JFrame parFrame;//父窗口

public StudentFrame (JFrame frame)
{
    parFrame = frame;
Container con = getContentPane();

setSize(WIDTH, HEIGHT);
setTitle("学生信息");
setResizable(false);//设置用户不可以改变框架的大小

StudentContentPanel contentPanel = new StudentContentPanel(studentIdCombox);
StudentButtonPanel buttonPanel = new StudentButtonPanel(parFrame, this, studentIdCombox);
con.add(contentPanel, BorderLayout.CENTER);
con.add(buttonPanel, BorderLayout.SOUTH);
    }
}class StudentContentPanel extends JPanel
{
    private JComboBox studentIdCombox;
    private JTextField studentName = new JTextField();
    private JTextField studentSpe = new JTextField();
   // private JTextArea studentId = new JTextArea( );
    
    private Student oneStudent;            
    private String strStudentId;//课程代码
    private String strStudentName;//课程名称
    private String strStudentSpe;//授课教师
   // private String strCourseDes;//课程简述
    
    private OperateStudent operateStudent;
    
    public StudentContentPanel(JComboBox id)
    {
        studentIdCombox = id;
        OperateStudent operateStudent = new OperateStudent();
        StudentStorage store = operateStudent.queryAllStudent();
        Vector vec = store.getStudentVec();
        
        //初始化时，如果数据库中没有相应的记录，相应的组件设置文本内容为空
        if(vec.size() == 0)
        {
            studentName.setText("");
            studentSpe.setText("");
            //courseDesArea.setText("");
        }
        //如果有记录，会根据当前选择的代码号，进行相应组件文本的设置
        else
        {
            for(int i = 0; i < vec.size(); i++)
            {
                oneStudent = (Student)vec.get(i);
                String studentId = oneStudent.getStudentID();
                studentIdCombox.addItem(studentId);
            }
            
            strStudentId = (String)studentIdCombox.getSelectedItem();
            
            //根据课程代码查询数据库相关的信息
            oneStudent = operateStudent.queryOneStudent(strStudentId);
            strStudentName = oneStudent.getStudentName();
            strStudentSpe = oneStudent.getStudentSpecialty();
            //strCourseDes = oneCourse.getCourseDes();
            studentName.setText(strStudentName);
            studentSpe.setText(strStudentSpe);
            //courseDesArea.setText(strCourseDes);            
        }
        //设置所有标签的字体
        Font labelFont = new Font("Dialog",Font.BOLD,14);
        
        // 构造第一个水平箱，并添加组件
        JLabel studentIdLabel = new JLabel("学  号:");
        studentIdLabel.setFont(labelFont);
        studentIdCombox.setPreferredSize(new Dimension(60, 30));
        Box hbox1 = Box.createHorizontalBox();
        hbox1.add(studentIdLabel);
        hbox1.add(Box.createHorizontalStrut(20));
        hbox1.add(studentIdCombox);        // 构造第二个水平箱，并添加组件
        JLabel studentNameLabel = new JLabel("姓  名:");
        studentNameLabel.setFont(labelFont);
        studentName.setEditable(false);
        studentName.setPreferredSize(new Dimension(60, 30));
        Box hbox2 = Box.createHorizontalBox();
        hbox2.add(studentNameLabel);
        hbox2.add(Box.createHorizontalStrut(20));
        hbox2.add(studentName);
        
        // 构造第三个水平箱，并添加组件
        JLabel studentSpeLabel = new JLabel("专  业：");
        studentSpeLabel.setFont(labelFont);
        studentSpe.setEditable(false);
        studentSpe.setPreferredSize(new Dimension(60, 30));
        Box hbox3 = Box.createHorizontalBox();
        hbox3.add(studentSpeLabel);
        hbox3.add(Box.createHorizontalStrut(20));
        hbox3.add(studentSpe);
        
         
        
        // 将四个箱体再添加到一个垂直箱中
        Box vbox = Box.createVerticalBox();
        vbox.add(hbox1);
        vbox.add(hbox2);        
        vbox.add(hbox3);
        
        
        add(vbox);
        
        //为下拉组合框添加事件监听器
        studentIdCombox.addActionListener(new ActionListener()
            {
                public void actionPerformed(ActionEvent e)
                {
                    strStudentId = (String)studentIdCombox.getSelectedItem();
                    oneStudent = new OperateStudent().queryOneStudent(strStudentId);
                    if(oneStudent != null)
                    {
                        strStudentName = oneStudent.getStudentName();
                        strStudentSpe = oneStudent.getStudentSpecialty();
                        //strCourseDes = oneCourse.getCourseDes();
                        
                        studentName.setText(strStudentName);
                        studentSpe.setText(strStudentSpe);
                        //courseDesArea.setText(strCourseDes);
                    }
                    else
                    {
                        studentName.setText("");
                        studentSpe.setText("");
                        //courseDesArea.setText("");
                    }
                }
            });        
    }
}class StudentButtonPanel extends JPanel
{
    private JFrame parFrame;
    private JFrame subFrame;
    private JComboBox studentIdCombox;
   // private JScrollPane gongdong=new JScrollPane(courseIdCombox);
    
    public StudentButtonPanel(JFrame par, JFrame sub, JComboBox id)
    {
        this.parFrame = par;
        this.subFrame = sub;
        this.studentIdCombox = id;
        
        JButton addButton = new JButton("添加学生");
        JButton deleteButton = new JButton("删除学生");       
        JButton exitButton = new JButton("退    出");
        
        this.add(addButton);
        this.add(deleteButton);        
        this.add(exitButton);
        
        //删除课程记录
        deleteButton.addActionListener(new ActionListener()
            {
                public void actionPerformed(ActionEvent e)
                {
                    String strStudentId = (String)studentIdCombox.getSelectedItem();
                    int i = JOptionPane.showConfirmDialog(null,"你确认要删除代码为" + strStudentId + "的学生吗？",
                        "删除课程",JOptionPane.YES_NO_OPTION);
                    if(i == 0)
                    {
                        int cou = new OperateStudent().deleteStudent(strStudentId);
                        if(cou == 1)
                        {
                            System.out.println("删除成功!");
                            studentIdCombox.removeItem(strStudentId);
                        }
                    }                    
                }
            });
        
        //添加课程记录
        addButton.addActionListener(new ActionListener()
            {
                public void actionPerformed(ActionEvent e)
                {
                    AddStudentFrame frame = new AddStudentFrame(subFrame, studentIdCombox);
                    subFrame.hide();
                    frame.show();
                }
            });            
        
        //返回父窗口
        exitButton.addActionListener(new ActionListener()
            {                        
         public void actionPerformed(ActionEvent e)
         {
         subFrame.hide();
         parFrame.show();
         }
            });
    }
}请老紫竹帮我分析一下哪出问题了，谢谢

Answer 2

at StudentFrame. <init>(StudentFrame.java:29)
at MainButtonPanel$MakeStudentFrameAction.actionPerformed(MainFrame.java:148) 
在这两行之前打印下相关的变量

Answer 3

可不可以把相关的类发给偶,不然不怎么好调.
因为你贴的这个类和其他的类有关
如果其它类都在,那就是很简单的调试问题了.
嘿嘿
如果需要的话:
发我邮箱[email protected]

Answer 4

at StudentContentPanel. <init>(StudentFrame.java:79) StudentFrame 的 79行。我看不出来是哪一行。
 oneStudent = operateStudent.queryOneStudent(strStudentId);也许这个 oneStudent  返回的是 null 吧！