我收到关于nullPointerException的错误，并且我的JavaSwing项目不会显示为结果。我想我需要在第55行将employeeInfoPanel初始化为JFrams，但我不知道如何做到这一点。之后可能还有其他错误。任何信息/提示将不胜感激！
package employee;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class taxSystemDriver1 extends JFrame {
private static final long serialVersionUID = 1L;
private JPanel homePanel, employeeInfoPanel, taxDetailsPanel, textInputPanel;
private JPanel ppsPanel, surnamePanel, firstnamePanel, dobPanel, salaryPanel, maritialStatusPanel,noIncomesPanel, noDependentChildrenPanel, noBIKPanel;
private JPanel buttonPanel, buttonPanelTop, buttonPanelBottom;
private JButton calculatorButton, recordsButton, addEmployeeButton, modifyEmployeeButton, deleteEmployeeButton, saveButton, backButton;
private JLabel comboLabel1, ppsLabel, surnameLabel, firstnameLabel, dobLabel, salaryLabel, maritialStatusLabel, noIncomesLabel, noDependentChildrenLabel, noBIKLabel;
private JLabel birthDayLabel, birthMonthLabel, birthYearLabel;
private JComboBox birthDayComboBox, birthMonthComboBox, birthYearComboBox, incomeComboBox;
private JRadioButton childrenRadioButton, maritialStatusRadioButton;
private JButton addEmployee, deleteEmployee, modifyEmployee, displayFirst, displayNext, displayLast, displayTaxDetails;
private JTextField ppsTF, surnameTF, firstnameTF, dobTF, salaryTF, maritialStatusTF, noIncomesTF, noDependentChildrenTF, noBIKTF;
private JTextArea statementTextArea;
private JScrollPane statementPane;
public taxSystemDriver1 (String title) {
super(title);
initComponents();
}
private void initComponents() {
setSize(300, 500);
setLocation(100, 100);
//construct components
//**************************************************************************
// HomePanel North
//**************************************************************************
//*********************************************
// EmployeeInfo Panel West
//*********************************************
// PPS NUMBER (TextField)
ppsPanel = new JPanel();
ppsLabel = new JLabel ("PPS Number: ");
ppsLabel.setHorizontalAlignment(SwingConstants.LEFT);
ppsTF = new JTextField (5);
ppsTF.setEditable(true);
ppsPanel.add(ppsLabel);
ppsPanel.add(ppsTF);
employeeInfoPanel.add(ppsPanel);
// SURNAME (TextField)
surnamePanel = new JPanel();
surnameLabel = new JLabel ("Employee Surname: ");
surnameLabel.setHorizontalAlignment(SwingConstants.LEFT);
surnameTF = new JTextField (5);
surnameTF.setEditable(true);
surnamePanel.add(surnameLabel);
surnamePanel.add(surnameTF);
employeeInfoPanel.add(surnamePanel);
// FIRST NAME (TextField)
firstnamePanel = new JPanel();
firstnameLabel = new JLabel ("Employee First Name: ");
firstnameLabel.setHorizontalAlignment(SwingConstants.LEFT);
firstnameTF = new JTextField (5);
firstnameTF.setEditable(true);
firstnamePanel.add(firstnameLabel);
firstnamePanel.add(firstnameTF);
employeeInfoPanel.add(firstnamePanel);
// DOB (ComboBox)
dobPanel = new JPanel();
dobPanel.add(new JLabel ("Employee Date of Birth: "));
String[] days = {"1","2","3","4","5","6","7","8","9","10","11","12","13","14","15",
"16","17","18","19","20","21","22","23","24","25","26","27","28",
"29","30","31"};
birthDayComboBox = new JComboBox(days);
dobPanel.add(birthDayComboBox);
String[] months = {"Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep",
"Oct", "Nov", "Dec"};
birthMonthComboBox = new JComboBox(months);
dobPanel.add(birthMonthComboBox);
String[] years = {"1996", "1995", "1994", "1993", "1992", "1991", "1990", "1989", "1988", "1987", "1986", "1985", "1984",
"1983", "1982", "1981", "1980", "1979", "1978", "1977", "1976", "1975", "1974", "1973", "1972", "1971", "1970",
"1969", "1968", "1967", "1966", "1965", "1964", "1963", "1962", "1961", "1960", "1959", "1958", "1957", "1956",
"1955", "1954", "1953", "1952", "1951", "1950", "1949", "1948", "1947", "1946", "1945", "1944", "1943", "1942",
"1941", "1940"};
birthYearComboBox = new JComboBox (years);
dobPanel.add(birthYearComboBox);
employeeInfoPanel.add(dobPanel);
//*********************************************
// TaxDetails Panel East
//*********************************************
// SALARY (TextField)
salaryPanel = new JPanel();
salaryLabel = new JLabel ("Employee yearly salary: €");
salaryLabel.setHorizontalAlignment(SwingConstants.LEFT);
salaryTF = new JTextField (5);
salaryTF.setEditable(true);
salaryPanel.add(salaryLabel);
salaryPanel.add(salaryTF);
taxDetailsPanel.add(salaryPanel);
// MARITIAL STATUS (Radio Button)
final ButtonGroup maritialStatus = new ButtonGroup();
maritialStatusPanel = new JPanel();
maritialStatusPanel.add(new JLabel("Relationship Status: "));
maritialStatusRadioButton = new JRadioButton ("Single", true);
maritialStatusRadioButton.setActionCommand("Single");
maritialStatus.add(maritialStatusRadioButton);
maritialStatusPanel.add(maritialStatusRadioButton);
maritialStatusRadioButton = new JRadioButton ("In unmarried Relationship");
maritialStatusRadioButton.setActionCommand("In unmarried Relationship");
maritialStatus.add(maritialStatusRadioButton);
maritialStatusPanel.add(maritialStatusRadioButton);
maritialStatusRadioButton = new JRadioButton ("Married");
maritialStatusRadioButton.setActionCommand("Married");
maritialStatus.add(maritialStatusRadioButton);
maritialStatusPanel.add(maritialStatusRadioButton);
taxDetailsPanel.add(maritialStatusRadioButton);
// NUMBER OF INCOMES IN HOUSEHOLD (ComboBox)
noIncomesPanel = new JPanel();
noIncomesPanel.add(new JLabel("Number of Incomes in the Household"));
String[] income = {"1", "2"};
incomeComboBox = new JComboBox(income);
noIncomesPanel.add(incomeComboBox);
taxDetailsPanel.add(incomeComboBox);
// NUMBER OF INDEPENDENT CHILDREN (Radio Button)
final ButtonGroup childrenNumber = new ButtonGroup();
noDependentChildrenPanel = new JPanel();
noDependentChildrenPanel.add(new JLabel("Number of Dependent Children: "));
childrenRadioButton = new JRadioButton ("0", true);
childrenRadioButton.setActionCommand("0");
childrenNumber.add(childrenRadioButton);
noDependentChildrenPanel.add(childrenRadioButton);
childrenRadioButton = new JRadioButton ("1");
childrenRadioButton.setActionCommand("1");
childrenNumber.add(childrenRadioButton);
noDependentChildrenPanel.add(childrenRadioButton);
childrenRadioButton = new JRadioButton ("2");
childrenRadioButton.setActionCommand("2");
childrenNumber.add(childrenRadioButton);
noDependentChildrenPanel.add(childrenRadioButton);
childrenRadioButton = new JRadioButton ("3");
childrenRadioButton.setActionCommand("3");
childrenNumber.add(childrenRadioButton);
noDependentChildrenPanel.add(childrenRadioButton);
childrenRadioButton = new JRadioButton ("4");
childrenRadioButton.setActionCommand("4");
childrenNumber.add(childrenRadioButton);
noDependentChildrenPanel.add(childrenRadioButton);
childrenRadioButton = new JRadioButton ("5");
childrenRadioButton.setActionCommand("5");
childrenNumber.add(childrenRadioButton);
noDependentChildrenPanel.add(childrenRadioButton);
taxDetailsPanel.add(childrenRadioButton);
// AMOUNT OF BENEFIT IN KIND (TextField)
noBIKPanel = new JPanel();
noBIKLabel = new JLabel ("Amount of benefits in kind : €");
noBIKLabel.setHorizontalAlignment(SwingConstants.LEFT);
noBIKTF = new JTextField (5);
noBIKTF.setEditable(true);
noBIKPanel.add(noBIKLabel);
noBIKPanel.add(noBIKTF);
taxDetailsPanel.add(noBIKPanel);
Container content = getContentPane();
content.setLayout(new BorderLayout());
content.add(homePanel, BorderLayout.NORTH);
homePanel.setLayout(new BorderLayout());
homePanel.add(employeeInfoPanel, BorderLayout.WEST);
homePanel.add(taxDetailsPanel, BorderLayout.EAST);
//*****************************************************
// ButtonGroup Panel Center
//*****************************************************
addEmployeeButton = new JButton("Add Employee");
modifyEmployeeButton = new JButton("Modify Employee");
deleteEmployeeButton = new JButton("Delete Employee");
displayFirst = new JButton("Display First Employee");
displayNext = new JButton("Display Next Employee");
displayLast = new JButton("Display Last Employee");
displayTaxDetails = new JButton("Display Employee Tax Details");
content.add(buttonPanel, BorderLayout.CENTER);
buttonPanel.setLayout(new BorderLayout());
buttonPanel.add(buttonPanelTop, BorderLayout.NORTH);
buttonPanel.add(buttonPanelBottom, BorderLayout.SOUTH);
buttonPanelTop.setLayout(new FlowLayout());
buttonPanelTop.add(addEmployeeButton);
buttonPanelTop.add(modifyEmployeeButton);
buttonPanelTop.add(deleteEmployeeButton);
buttonPanelBottom.setLayout(new FlowLayout());
buttonPanelBottom.add(displayFirst);
buttonPanelBottom.add(displayLast);
buttonPanelBottom.add(displayNext);
buttonPanelBottom.add(displayTaxDetails);
}
/*employeeInfoPanel = new JPanel();
employeeInfoPanel.setLayout(new GridLayout(7, 1));
public static void main(String[] args)
{
JFrame taxFrame = new taxSystemDriver1("Tax and Revenue System");
taxFrame.setVisible(true);
答案 0 :(得分：0)
您正在调用一个不存在的对象上的方法（employeeInfoPanel是一个从未在#add（...）方法调用之前构造或赋值的属性）。
初始化employeeInfoPanel，这是一个简单的默认构造：
employeeInfoPanel = new JPanel();