使用bean类填充Jtextfield时出现nullpointerexception

Question

这是我的类，这是一个gui由两个选项卡组成，我的个人资料和编辑个人资料。当索引值更改为1时，我在"myProfileTabStateChanged"方法中遇到问题。当标签索引为0时，'myProfile()'方法执行成功，但当索引为1时，'editProfile()'给出太多错误。editprofile()的目的只是从bean类中提取值，并将其适当地设置为文本字段。我做错了什么?请注意，bean类变量正在使用setter方法正确填充，但是在这个类中，我无法使用getter方法检索值?也许它正在检索，但问题在于无法将其设置为文本字段。

public class MainMenu extends javax.swing.JFrame {
    Academic ac = new Academic();
    academicBean bn = new academicBean();
    /**
     * Creates new form MainMenu
     */
    public MainMenu() {
        initComponents();
        // myProfile(); 
        // editProfile(); 
    }
    public void myProfile() {
        ac.retrieveAcademic();
        nameLabel.setText(""+ac.title+" "+ac.forename+" "+ac.surname);
        roleLabel.setText("Role:    " + ac.role);
        roomLabel.setText("Room:    " + ac.room);
        pageLabel.setText("Page:    " + ac.page);
        hoursLabel.setText("Hours:   " + ac.hours);
        phoneLabel.setText("Phone:   " + ac.phone);
        mobileLabel.setText("Mobile:  " + ac.mobile);
        emailLabel.setText("Email:   " + ac.email);
        imageLabel.setIcon(ac.format);
    }
    public void editProfile() {
        ac.retrieveAcademic();
        idLabel.setText("Academic Id:    "+bn.getAcademicId());
        txt_title.setSelectedItem(bn.getTitle().toString());
        txt_fn.setText(bn.getForename().toString());
        txt_ln.setText(bn.getSurname().toString());
        combo_role.setSelectedItem(bn.getRole().toString());
        txt_room.setText(bn.getRoom().toString());
        txt_page.setText(bn.getPage().toString());
        txt_hours.setText(bn.getHours().toString());
        txt_phone.setText(bn.getPhone().toString());
        txt_mobile.setText(bn.getMobile().toString());
        txt_email.setText(bn.getEmail().toString());
    }
    private void myProfileTabStateChanged(javax.swing.event.ChangeEvent evt) {
        JTabbedPane sourceTabbedPane = (JTabbedPane) evt.getSource();
        int index = sourceTabbedPane.getSelectedIndex();
            if (index == 0) {
            myProfile();
        }
        else if (index == 1) {
            editProfile(); 
        }
    }

//Class Academic

public class Academic extends javax.swing.JFrame {
   String filename = null;
   int s = 0;
   byte[] person_image = null;
   ImageIcon format = null;
   LoginBean l = new LoginBean();
   Connection con = javaconnect.ConnectDB();
   academicBean bean = new academicBean();
   PreparedStatement pst = null;
   ResultSet rs = null;
   int id;
   String title;
   String titleValue;
   String forename;
   String surname;
   String role;
   String roleValue;
   String room;
   String page;
   String hours;
   String phone;
   String mobile;
   String email;
   byte[] imagedata = null;
   public Academic() {
      initComponents();
   }
   @SuppressWarnings("unchecked")
   public void retrieveAcademic() {
      try {
         pst = con
               .prepareStatement("SELECT * FROM AcademicInfo where Email=? and Password=?");
         pst.setString(1, l.getUsername());
         pst.setString(2, l.getPassword());
         rs = pst.executeQuery();
         while (rs.next()) {
            id = (rs.getInt(1));
            bean.setAcademicId(id);
            title = (rs.getString(2));
            bean.setTitle(title);
            forename = (rs.getString(3));
            bean.setForename(forename);
            surname = (rs.getString(4));
            bean.setSurname(surname);
            role = (rs.getString(5));
            bean.setRole(role);
            room = (rs.getString(6));
            bean.setRoom(room);
            page = (rs.getString(7));
            bean.setPage(page);
            hours = (rs.getString(8));
            bean.setHours(hours);
            phone = (rs.getString(9));
            bean.setPhone(phone);
            mobile = (rs.getString(10));
            bean.setMobile(mobile);
            email = (rs.getString(11));
            bean.setEmail(email);
            imagedata = (rs.getBytes("Image"));
            format = new ImageIcon(imagedata);
         } // end while
      } catch (SQLException ex) {
         Logger lgr = Logger.getLogger(Academic.class.getName());
         lgr.log(Level.SEVERE, ex.getMessage(), ex);
      } finally {
         try {
            if (rs != null) {
               rs.close();
            }
            if (pst != null) {
               pst.close();
            }
            if (con != null) {
               con.close();
            }
         } catch (SQLException ex) {
            Logger lgr = Logger.getLogger(Academic.class.getName());
            lgr.log(Level.WARNING, ex.getMessage(), ex);
         }
      }
   }
}

//类

public class AcademicBean {
private int academicid;
private String title;
private String forename;
private String surname;
private String role;
private String room;
private String page;
private String hours;
private String phone;
private String mobile;
private String email;
private byte []  image;
private String pass; 
 //Setters
public void setAcademicId (int academicid) {
    this.academicid = academicid;
}   
public void setTitle(String title) {
    this.title = title;
}   
public void setForename(String forename) {
    this.forename = forename;
}
public void setSurname(String surname) {
    this.surname = surname;
}
public void setRole(String role) {
    this.role = role;
}
public void setRoom(String room) {
    this.room = room;
}
public void setPage(String page) {
    this.page = page;
}
public void setHours(String hours) {
    this.hours = hours;
}
public void setPhone(String phone) {
    this.phone = phone;
}
public void setMobile(String mobile) {
    this.mobile = mobile;
}
public void setEmail(String email) {
    this.email = email;
}
public void setImage (byte [] image) {
     this.image = image; 
 }
public void setPassword (String pass) {
     this.pass= pass;
 }

//Gettters 
public String getPassword () {
     return pass;  
 }
public int getAcademicId() {
     return academicid; 
 }

public byte [] getImage() {
     return image;
 }
public String getTitle() {
    return title;
}
public String getForename() {
    return forename;
}
public String getSurname() {
    return surname;
}
public String getRole() {
    return role;
}
public String getRoom() {
    return room;
}
public String getPage() {
    return page;
}
public String getHours() {
    return hours;
}
public String getPhone() {
    return phone;
}
public String getMobile() {
    return mobile;
}
public String getEmail() {
    return email;
}
}

异常堆栈

//

<>之前线程"AWT-EventQueue-0"中的异常在org.sqlite.PrepStmt。(PrepStmt.java: 37)org.sqlite.Conn.prepareStatement (Conn.java: 231)org.sqlite.Conn.prepareStatement (Conn.java: 224)org.sqlite.Conn.prepareStatement (Conn.java: 213)eecsCRM.Academic.retrieveAcademic (Academic.java: 68)eecsCRM.MainMenu.editProfile (MainMenu.java: 50)eecsCRM.MainMenu.myProfileTabStateChanged (MainMenu.java: 569)eecsCRM.MainMenu.access 300美元(MainMenu.java: 13)eecsCRM.MainMenu statechange 4.美元(MainMenu.java: 194)javax.swing.JTabbedPane.fireStateChanged (JTabbedPane.java: 400)javax.swing.JTabbedPane ModelListener.stateChanged美元(JTabbedPane.java: 253)javax.swing.DefaultSingleSelectionModel.fireStateChanged (DefaultSingleSelectionModel.java: 116)javax.swing.DefaultSingleSelectionModel.setSelectedIndex (DefaultSingleSelectionModel.java: 50)javax.swing.JTabbedPane.setSelectedIndexImpl (JTabbedPane.java: 599)javax.swing.JTabbedPane.setSelectedIndex (JTabbedPane.java: 574)javax.swing.plaf.basic.BasicTabbedPaneUI Handler.mousePressed美元(BasicTabbedPaneUI.java: 3628)javax.swing.plaf.synth.SynthTabbedPaneUI mousepressed 1.美元(SynthTabbedPaneUI.java: 279)java.awt.AWTEventMulticaster.mousePressed (AWTEventMulticaster.java: 262)java.awt.Component.processMouseEvent (Component.java: 6264)javax.swing.JComponent.processMouseEvent (JComponent.java: 3267)java.awt.Component.processEvent (Component.java: 6032)java.awt.Container.processEvent (Container.java: 2041)java.awt.Component.dispatchEventImpl (Component.java: 4630)java.awt.Container.dispatchEventImpl (Container.java: 2099)java.awt.Component.dispatchEvent (Component.java: 4460)java.awt.LightweightDispatcher.retargetMouseEvent (Container.java: 4577)java.awt.LightweightDispatcher.processMouseEvent (Container.java: 4235)java.awt.LightweightDispatcher.dispatchEvent (Container.java: 4168)java.awt.Container.dispatchEventImpl (Container.java: 2085)java.awt.Window.dispatchEventImpl (Window.java: 2478)java.awt.Component.dispatchEvent (Component.java: 4460)java.awt.EventQueue.dispatchEvent (EventQueue.java: 599)java.awt.EventDispatchThread.pumpOneEventForFilters (EventDispatchThread.java: 269)java.awt.EventDispatchThread.pumpEventsForFilter (EventDispatchThread.java: 184)java.awt.EventDispatchThread.pumpEventsForHierarchy (EventDispatchThread.java: 174)java.awt.EventDispatchThread.pumpEvents (EventDispatchThread.java: 169)java.awt.EventDispatchThread.pumpEvents (EventDispatchThread.java: 161)java.awt.EventDispatchThread.run (EventDispatchThread.java: 122)

Answer 1

只是一个粗略的猜测:您似乎至少有两个完全不相关的academicBean对象(注意该类应该命名为 a academicBean)，一个在Academic中，一个在MainMenu中。我怀疑他们应该是同一个人。

也许主菜单应该有:

academicBean bn = ac.getAcademicBean(); 

和Academic have:

public academicBean getAcademicBean() {
   return bean;
}

以便MainMenu可以提取Academic的bean，使bean变量指向同一个bean对象。