我只是想请求帮助，因为我不知道这个错误是否导致我的程序无法运行。
在我去寻求帮助之前，我做了一些测试和重新调试，以便在我尝试运行程序时找到错误导致的根源。见下面的代码
public class AcademicPersonnelForm{
public AcademicPersonnelForm(){
create();
}
public static void main(String [] args){
SwingUtilities.invokeLater(new Runnable(){
public void run(){
new AcademicPersonnelForm();
}
});
}//close main
下面是我创建JFrame的方法“create（）”。在这个方法中，我声明了我需要在框架中插入的所有必要组件。（仅在发生错误的地方包含组件）
public void create(){
gbc.fill = GridBagConstraints.NONE;
gbc.anchor = GridBagConstraints.LINE_START;
gbc.ipady = 20;
gbc.ipadx = 20;
gbc.gridx = 1;
gbc.gridy = 0;
gbc.gridwidth = 1;
gbc.gridheight = 1;
textEmpNo.addKeyListener(new MyRetrieve());
textEmpNo.setPreferredSize(new Dimension(80,5));
textEmpNo.setDocument(new LengthRestrictedDocument(3));
//add textEmpNo in the main panel
gbl.setConstraints(textEmpNo, gbc);
mainPanel.add(textEmpNo);
}
我发现上面提到的错误出现在“textEmpNo.addKeyListener（new MyRetrieve（））;”中，因为当我尝试在此代码中添加注释时，程序运行正常。
“new MyRetrieve（）”是我可以生成和检索员工编号的子类。见下面的代码。
public class MyRetrieve implements KeyListener{
search_employee_record_db serdb = new search_employee_record_db();
generate_emp_num_db gendb = new generate_emp_num_db();
public void keyReleased(KeyEvent e){
if(e.getKeyCode() == KeyEvent.VK_ENTER){
serdb.EMPNUM = textEmpNo.getText();
//if(serdb.EmpNo.equals(textEmpNo.getText())){
if(textEmpNo.getText().equals(serdb.EMPNUM)){
serdb.retrieved();
//textEmpNo.setText(serdb.EmpNo);
textFName.setText(serdb.FName);
textLName.setText(serdb.LName);
comboGender.setSelectedItem(serdb.GENDER);
textAddress.setText(serdb.address);
comboDay.setSelectedItem(serdb.DAY);
comboMonth.setSelectedItem(serdb.MONTH);
comboYear.setSelectedItem(serdb.YEAR);
textSSS.setText(serdb.sss);
textReligion.setText(serdb.religion);
textCitizenship.setText(serdb.citizenship);
textTIN.setText(serdb.tin);
textMobileNo.setText(serdb.mobileNumber);
comboStatus.setSelectedItem(serdb.STATUS);
comboDHDay.setSelectedItem(serdb.DH_DAY);
comboDHMonth.setSelectedItem(serdb.DH_MONTH);
comboDHYear.setSelectedItem(serdb.DH_YEAR);
update.setEnabled(true);
}//end of if
if(serdb.EMPNUM.equalsIgnoreCase("")){
gendb.generate();
textEmpNo.setText(gendb.INC);
comboGender.setSelectedIndex(0);
comboMonth.setSelectedIndex(0);
comboDay.setSelectedIndex(0);
comboYear.setSelectedIndex(0);
comboDHMonth.setSelectedIndex(0);
comboDHDay.setSelectedIndex(0);
comboDHYear.setSelectedIndex(0);
comboStatus.setSelectedIndex(0);
textLName.setText("");
textFName.setText("");
textAddress.setText("");
textSSS.setText("");
textReligion.setText("");
textTIN.setText("");
textCitizenship.setText("");
textMobileNo.setText("");
}//end of if
else if(!textEmpNo.getText().equals(serdb.EmpNo)){
comboGender.setSelectedIndex(0);
comboMonth.setSelectedIndex(0);
comboDay.setSelectedIndex(0);
comboYear.setSelectedIndex(0);
comboDHMonth.setSelectedIndex(0);
comboDHDay.setSelectedIndex(0);
comboDHYear.setSelectedIndex(0);
comboStatus.setSelectedIndex(0);
textLName.setText("");
textFName.setText("");
textAddress.setText("");
textSSS.setText("");
textReligion.setText("");
textTIN.setText("");
textCitizenship.setText("");
textMobileNo.setText("");
JOptionPane.showMessageDialog(null,"employee number does not exist");
textEmpNo.selectAll();
}//end of else if
}//end of outer if
} //end method
public void keyTyped(KeyEvent e) {
// TODO: Do something for the keyTyped event
}
public void keyPressed(KeyEvent e) {
// TODO: Do something for the keyPressed event
}
}//close inner class
有人可以向我解释为什么上面提到的错误发生了。感谢