有两个问题，
第一个：
不好：
if (workerType.getSelectedItem().toString() == "Salaried"){。使用equals（…）或equalsIgnoreCase（…）。理解==检查是否绝对不是您感兴趣的 引用 相等性。您需要 函数
相等性，这是方法要测试的。
所以：
if ("Salaried".equalsIgnoreCase(workerType.getSelectedItem().toString())){第二：
AddEmployeeDialog frame = new AddEmployeeDialog(new Employeeframe());
您要传入一个 新的 Employeeframe对象，这意味着您正在为错误的Employeeframe更新列表模型。而是传递 可视化的
Employeeframe。
更改为：
AddEmployeeDialog frame = new AddEmployeeDialog(Employeeframe.this);
我创建的程序可以缩小您的代码，但仍然允许其运行并演示您的问题：
import java.awt.BorderLayout;import java.awt.event.*;import javax.swing.*;import javax.swing.border.TitledBorder;@SuppressWarnings("serial")public class Employeeframe extends Jframe implements ActionListener { private JButton addButton; private DefaultListModel<Employee> listModel; private JList<Employee> employeeList; public Employeeframe() { super("Employee Manager"); setLocationByPlatform(true); setDefaultCloseOperation(EXIT_ON_CLOSE); listModel = new DefaultListModel<>(); employeeList = new JList<>(listModel); JScrollPane employeeScroll = new JScrollPane(employeeList); employeeScroll.setBorder(new TitledBorder("Employee List")); addButton = new JButton("Add Employee"); addButton.addActionListener(this); Box topBox = Box.createHorizontalBox(); topBox.add(addButton); getContentPane().setLayout(new BorderLayout()); getContentPane().add(topBox, BorderLayout.NORTH); getContentPane().add(employeeScroll, BorderLayout.CENTER); pack(); } public DefaultListModel<Employee> getListModel() { return this.listModel; } @Override public void actionPerformed(ActionEvent event) { Object source = event.getSource(); if (source == addButton) { // !! AddEmployeeDialog frame = new AddEmployeeDialog(new Employeeframe()); AddEmployeeDialog frame = new AddEmployeeDialog(Employeeframe.this); frame.setVisible(true); } } public static void main(String[] args) { SwingUtilities.invokeLater(new Runnable() { public void run() { new Employeeframe().setVisible(true); } }); }}@SuppressWarnings("serial")class AddEmployeeDialog extends JDialog implements ActionListener { private JComboBox<String> workerType; private JTextField givenNameField; private JTextField familyNameField; private JButton okButton; private JButton cancelButton; private Employeeframe employeeframe; public AddEmployeeDialog(final Employeeframe frame) { super(frame, "Add Employee", true); setLocationRelativeTo(employeeframe); this.employeeframe = frame; workerType = new JComboBox<String>(Employee.getEmployeeTypes()); givenNameField = new JTextField(20); familyNameField = new JTextField(20); Box workerBox = Box.createHorizontalBox(); workerBox.add(new JLabel("Worker type")); workerBox.add(workerType); workerBox.add(new JLabel("Start date")); Box givenNameBox = Box.createHorizontalBox(); givenNameBox.add(new JLabel("Given name ")); givenNameBox.add(givenNameField); Box familyNameBox = Box.createHorizontalBox(); familyNameBox.add(new JLabel("Family name")); familyNameBox.add(familyNameField); workerType.setSelectedItem(null); // Create buttons and add the current class as an ActionListener okButton = new JButton("OK"); okButton.addActionListener(this); cancelButton = new JButton("Cancel"); cancelButton.addActionListener(this); Box bottomBox = Box.createHorizontalBox(); bottomBox.add(Box.createHorizontalGlue()); bottomBox.add(okButton); bottomBox.add(Box.createHorizontalGlue()); bottomBox.add(cancelButton); bottomBox.add(Box.createHorizontalGlue()); // Lay out the GUI getContentPane().setLayout(new BoxLayout(getContentPane(), BoxLayout.Y_AXIS)); getContentPane().add(workerBox); getContentPane().add(givenNameBox); getContentPane().add(familyNameBox); getContentPane().add(Box.createVerticalStrut(10)); getContentPane().add(bottomBox); pack(); } @Override public void actionPerformed(ActionEvent event) { Object source = event.getSource(); if (source == okButton) { System.out.println("here"); System.out.println(workerType.getSelectedItem()); if ("Salaried".equalsIgnoreCase(workerType.getSelectedItem().toString())) { Employee employee = new Employee("Salaried", givenNameField.getText(), familyNameField.getText()); employeeframe.getListModel().addElement(employee); } else { Employee employee = new Employee("Hourly", givenNameField.getText(), familyNameField.getText()); employeeframe.getListModel().addElement(employee); } } dispose(); }}class Employee { private static final String[] EMPLOYEE_TYPES = { "Salaried", "Hourly" }; private String givenName; private String familyName; private String type; public Employee(String type, String givenName, String familyName) { this.type = type; this.givenName = givenName; this.familyName = familyName; } public static String[] getEmployeeTypes() { return EMPLOYEE_TYPES; } public String getGivenName() { return givenName; } public String getFamilyName() { return familyName; } public String getType() { return type; } @Override public String toString() { return String.format("Employee: %s, %s %s", type, givenName, familyName); }}
