diff --git a/src/com/personalproject/ui/DesktopApp.java b/src/com/personalproject/ui/DesktopApp.java
new file mode 100644
index 0000000..61e1e26
--- /dev/null
+++ b/src/com/personalproject/ui/DesktopApp.java
@@ -0,0 +1,658 @@
+package com.personalproject.ui;
+
+import com.personalproject.controller.MathLearningController;
+import com.personalproject.generator.HighSchoolQuestionGenerator;
+import com.personalproject.generator.MiddleSchoolQuestionGenerator;
+import com.personalproject.generator.PrimaryQuestionGenerator;
+import com.personalproject.generator.QuestionGenerator;
+import com.personalproject.model.DifficultyLevel;
+import com.personalproject.model.ExamSession;
+import com.personalproject.model.QuizQuestion;
+import com.personalproject.service.QuestionGenerationService;
+import java.awt.BorderLayout;
+import java.awt.CardLayout;
+import java.awt.Dimension;
+import java.awt.EventQueue;
+import java.awt.GridBagConstraints;
+import java.awt.GridBagLayout;
+import java.awt.Insets;
+import java.util.EnumMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+import javax.swing.BorderFactory;
+import javax.swing.ButtonGroup;
+import javax.swing.JButton;
+import javax.swing.JComboBox;
+import javax.swing.JFrame;
+import javax.swing.JLabel;
+import javax.swing.JOptionPane;
+import javax.swing.JPanel;
+import javax.swing.JPasswordField;
+import javax.swing.JRadioButton;
+import javax.swing.JScrollPane;
+import javax.swing.JSpinner;
+import javax.swing.JTextArea;
+import javax.swing.JTextField;
+import javax.swing.SpinnerNumberModel;
+
+/**
+ * A Swing desktop application that drives the math learning backend.
+ */
+public final class DesktopApp extends JFrame {
+
+  private static final String CARD_LOGIN = "login";
+  private static final String CARD_REGISTER = "register";
+  private static final String CARD_VERIFY = "verify";
+  private static final String CARD_SET_PASSWORD = "set_password";
+  private static final String CARD_CHANGE_PASSWORD = "change_password";
+  private static final String CARD_SELECT = "select";
+  private static final String CARD_EXAM = "exam";
+  private static final String CARD_SCORE = "score";
+
+  private final MathLearningController controller;
+  private final CardLayout cardLayout;
+  private final JPanel cards;
+
+  private String currentUsername = "";
+  private ExamSession currentExamSession;
+  private int currentSelectedAnswerIndex = -1;
+
+  public DesktopApp() {
+    super("数学学习桌面应用");
+    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
+    setMinimumSize(new Dimension(820, 640));
+
+    Map<DifficultyLevel, QuestionGenerator> generatorMap = new EnumMap<>(DifficultyLevel.class);
+    generatorMap.put(DifficultyLevel.PRIMARY, new PrimaryQuestionGenerator());
+    generatorMap.put(DifficultyLevel.MIDDLE, new MiddleSchoolQuestionGenerator());
+    generatorMap.put(DifficultyLevel.HIGH, new HighSchoolQuestionGenerator());
+    QuestionGenerationService questionGenerationService = new QuestionGenerationService(
+        generatorMap);
+    this.controller = new MathLearningController(generatorMap, questionGenerationService);
+
+    this.cardLayout = new CardLayout();
+    this.cards = new JPanel(cardLayout);
+
+    cards.add(buildLoginPanel(), CARD_LOGIN);
+    cards.add(buildRegisterPanel(), CARD_REGISTER);
+    cards.add(buildVerifyPanel(), CARD_VERIFY);
+    cards.add(buildSetPasswordPanel(), CARD_SET_PASSWORD);
+    cards.add(buildChangePasswordPanel(), CARD_CHANGE_PASSWORD);
+    cards.add(buildSelectPanel(), CARD_SELECT);
+    cards.add(buildExamPanel(), CARD_EXAM);
+    cards.add(buildScorePanel(), CARD_SCORE);
+
+    getContentPane().setLayout(new BorderLayout());
+    getContentPane().add(cards, BorderLayout.CENTER);
+    cardLayout.show(cards, CARD_LOGIN);
+  }
+
+  private JPanel buildLoginPanel() {
+    JPanel panel = new JPanel(new GridBagLayout());
+    panel.setBorder(BorderFactory.createEmptyBorder(24, 24, 24, 24));
+    GridBagConstraints gc = baseGbc();
+
+    JLabel title = new JLabel("登录");
+    title.setFont(title.getFont().deriveFont(20f));
+    gc.gridwidth = 2;
+    panel.add(title, gc);
+
+    gc.gridy++;
+    gc.gridwidth = 1;
+    panel.add(new JLabel("用户名:"), gc);
+    JTextField usernameField = new JTextField(18);
+    gc.gridx = 1;
+    panel.add(usernameField, gc);
+
+    gc.gridy++;
+    gc.gridx = 0;
+    panel.add(new JLabel("密码:"), gc);
+    JPasswordField passwordField = new JPasswordField(18);
+    gc.gridx = 1;
+    panel.add(passwordField, gc);
+
+    gc.gridy++;
+    gc.gridx = 0;
+    JButton loginBtn = new JButton("登录");
+    panel.add(loginBtn, gc);
+    gc.gridx = 1;
+    JButton toRegisterBtn = new JButton("注册");
+    panel.add(toRegisterBtn, gc);
+
+    gc.gridy++;
+    gc.gridx = 0;
+    JButton toChangePwd = new JButton("修改密码");
+    panel.add(toChangePwd, gc);
+
+    loginBtn.addActionListener(e -> {
+      String username = usernameField.getText().trim();
+      String password = String.valueOf(passwordField.getPassword());
+      if (username.isEmpty() || password.isEmpty()) {
+        showError("请输入用户名和密码");
+        return;
+      }
+      Optional<com.personalproject.auth.UserAccount> account = controller.authenticate(username,
+          password);
+      if (account.isPresent()) {
+        currentUsername = username;
+        cardLayout.show(cards, CARD_SELECT);
+      } else {
+        showError("登录失败：用户名或密码错误，或未完成注册");
+      }
+    });
+
+    toRegisterBtn.addActionListener(e -> cardLayout.show(cards, CARD_REGISTER));
+    toChangePwd.addActionListener(e -> cardLayout.show(cards, CARD_CHANGE_PASSWORD));
+
+    return panel;
+  }
+
+  private JPanel buildRegisterPanel() {
+    JPanel panel = new JPanel(new GridBagLayout());
+    panel.setBorder(BorderFactory.createEmptyBorder(24, 24, 24, 24));
+    GridBagConstraints gc = baseGbc();
+
+    JLabel title = new JLabel("用户注册");
+    title.setFont(title.getFont().deriveFont(20f));
+    gc.gridwidth = 2;
+    panel.add(title, gc);
+
+    gc.gridy++;
+    gc.gridwidth = 1;
+    panel.add(new JLabel("用户名:"), gc);
+    JTextField usernameField = new JTextField(18);
+    gc.gridx = 1;
+    panel.add(usernameField, gc);
+
+    gc.gridy++;
+    gc.gridx = 0;
+    panel.add(new JLabel("邮箱:"), gc);
+    JTextField emailField = new JTextField(18);
+    gc.gridx = 1;
+    panel.add(emailField, gc);
+
+    gc.gridy++;
+    gc.gridx = 0;
+    panel.add(new JLabel("难度:"), gc);
+    JComboBox<DifficultyLevel> levelBox = new JComboBox<>(DifficultyLevel.values());
+    gc.gridx = 1;
+    panel.add(levelBox, gc);
+
+    gc.gridy++;
+    gc.gridx = 0;
+    JButton sendCodeBtn = new JButton("发送注册码");
+    panel.add(sendCodeBtn, gc);
+    gc.gridx = 1;
+    JButton backBtn = new JButton("返回登录");
+    panel.add(backBtn, gc);
+
+    sendCodeBtn.addActionListener(e -> {
+      String username = usernameField.getText().trim();
+      String email = emailField.getText().trim();
+      DifficultyLevel level = (DifficultyLevel) levelBox.getSelectedItem();
+      if (username.isEmpty() || email.isEmpty() || level == null) {
+        showError("请填写完整信息");
+        return;
+      }
+      if (!controller.isValidEmail(email)) {
+        showError("邮箱格式不正确");
+        return;
+      }
+      boolean ok = controller.initiateRegistration(username, email, level);
+      if (ok) {
+        currentUsername = username;
+        JOptionPane.showMessageDialog(this, "注册码已发送到邮箱（示例中输出到控制台）");
+        cardLayout.show(cards, CARD_VERIFY);
+      } else {
+        showError("注册启动失败：用户名已存在或邮箱已注册");
+      }
+    });
+
+    backBtn.addActionListener(e -> cardLayout.show(cards, CARD_LOGIN));
+    return panel;
+  }
+
+  private JPanel buildVerifyPanel() {
+    JPanel panel = new JPanel(new GridBagLayout());
+    panel.setBorder(BorderFactory.createEmptyBorder(24, 24, 24, 24));
+    GridBagConstraints gc = baseGbc();
+
+    JLabel title = new JLabel("输入邮箱收到的注册码");
+    title.setFont(title.getFont().deriveFont(18f));
+    gc.gridwidth = 2;
+    panel.add(title, gc);
+
+    gc.gridy++;
+    gc.gridwidth = 1;
+    panel.add(new JLabel("用户名:"), gc);
+    JTextField usernameField = new JTextField(18);
+    gc.gridx = 1;
+    panel.add(usernameField, gc);
+
+    gc.gridy++;
+    gc.gridx = 0;
+    panel.add(new JLabel("注册码:"), gc);
+    JTextField codeField = new JTextField(18);
+    gc.gridx = 1;
+    panel.add(codeField, gc);
+
+    gc.gridy++;
+    gc.gridx = 0;
+    JButton verifyBtn = new JButton("验证");
+    panel.add(verifyBtn, gc);
+    gc.gridx = 1;
+    JButton backBtn = new JButton("返回");
+    panel.add(backBtn, gc);
+
+    verifyBtn.addActionListener(e -> {
+      String username = usernameField.getText().trim();
+      String code = codeField.getText().trim();
+      if (username.isEmpty() || code.isEmpty()) {
+        showError("请输入用户名与注册码");
+        return;
+      }
+      boolean ok = controller.verifyRegistrationCode(username, code);
+      if (ok) {
+        currentUsername = username;
+        JOptionPane.showMessageDialog(this, "验证成功，请设置密码");
+        cardLayout.show(cards, CARD_SET_PASSWORD);
+      } else {
+        showError("验证失败：注册码错误或超出尝试次数");
+      }
+    });
+
+    backBtn.addActionListener(e -> cardLayout.show(cards, CARD_REGISTER));
+    return panel;
+  }
+
+  private JPanel buildSetPasswordPanel() {
+    JPanel panel = new JPanel(new GridBagLayout());
+    panel.setBorder(BorderFactory.createEmptyBorder(24, 24, 24, 24));
+    GridBagConstraints gc = baseGbc();
+
+    JLabel title = new JLabel("设置密码（6-10位，含大小写字母和数字）");
+    title.setFont(title.getFont().deriveFont(18f));
+    gc.gridwidth = 2;
+    panel.add(title, gc);
+
+    gc.gridy++;
+    gc.gridwidth = 1;
+    panel.add(new JLabel("用户名:"), gc);
+    JTextField usernameField = new JTextField(18);
+    gc.gridx = 1;
+    panel.add(usernameField, gc);
+
+    gc.gridy++;
+    gc.gridx = 0;
+    panel.add(new JLabel("密码:"), gc);
+    JPasswordField pwd1 = new JPasswordField(18);
+    gc.gridx = 1;
+    panel.add(pwd1, gc);
+
+    gc.gridy++;
+    gc.gridx = 0;
+    panel.add(new JLabel("确认密码:"), gc);
+    JPasswordField pwd2 = new JPasswordField(18);
+    gc.gridx = 1;
+    panel.add(pwd2, gc);
+
+    gc.gridy++;
+    gc.gridx = 0;
+    JButton setBtn = new JButton("设置密码");
+    panel.add(setBtn, gc);
+    gc.gridx = 1;
+    JButton backBtn = new JButton("返回");
+    panel.add(backBtn, gc);
+
+    setBtn.addActionListener(e -> {
+      String username = usernameField.getText().trim();
+      String p1 = String.valueOf(pwd1.getPassword());
+      String p2 = String.valueOf(pwd2.getPassword());
+      if (username.isEmpty() || p1.isEmpty() || p2.isEmpty()) {
+        showError("请填写完整信息");
+        return;
+      }
+      if (!p1.equals(p2)) {
+        showError("两次密码不一致");
+        return;
+      }
+      if (!controller.isValidPassword(p1)) {
+        showError("密码不符合要求：6-10位，含大小写字母和数字");
+        return;
+      }
+      boolean ok = controller.setPassword(username, p1);
+      if (ok) {
+        currentUsername = username;
+        JOptionPane.showMessageDialog(this, "密码设置成功，请登录");
+        cardLayout.show(cards, CARD_LOGIN);
+      } else {
+        showError("设置失败：请确认已完成注册或用户存在");
+      }
+    });
+
+    backBtn.addActionListener(e -> cardLayout.show(cards, CARD_VERIFY));
+    return panel;
+  }
+
+  private JPanel buildChangePasswordPanel() {
+    JPanel panel = new JPanel(new GridBagLayout());
+    panel.setBorder(BorderFactory.createEmptyBorder(24, 24, 24, 24));
+    GridBagConstraints gc = baseGbc();
+
+    JLabel title = new JLabel("修改密码");
+    title.setFont(title.getFont().deriveFont(18f));
+    gc.gridwidth = 2;
+    panel.add(title, gc);
+
+    gc.gridy++;
+    gc.gridwidth = 1;
+    panel.add(new JLabel("用户名:"), gc);
+    JTextField usernameField = new JTextField(18);
+    gc.gridx = 1;
+    panel.add(usernameField, gc);
+
+    gc.gridy++;
+    gc.gridx = 0;
+    panel.add(new JLabel("原密码:"), gc);
+    JPasswordField oldPwd = new JPasswordField(18);
+    gc.gridx = 1;
+    panel.add(oldPwd, gc);
+
+    gc.gridy++;
+    gc.gridx = 0;
+    panel.add(new JLabel("新密码:"), gc);
+    JPasswordField newPwd1 = new JPasswordField(18);
+    gc.gridx = 1;
+    panel.add(newPwd1, gc);
+
+    gc.gridy++;
+    gc.gridx = 0;
+    panel.add(new JLabel("确认新密码:"), gc);
+    JPasswordField newPwd2 = new JPasswordField(18);
+    gc.gridx = 1;
+    panel.add(newPwd2, gc);
+
+    gc.gridy++;
+    gc.gridx = 0;
+    JButton changeBtn = new JButton("修改");
+    panel.add(changeBtn, gc);
+    gc.gridx = 1;
+    JButton backBtn = new JButton("返回登录");
+    panel.add(backBtn, gc);
+
+    changeBtn.addActionListener(e -> {
+      String username = usernameField.getText().trim();
+      String old = String.valueOf(oldPwd.getPassword());
+      String n1 = String.valueOf(newPwd1.getPassword());
+      String n2 = String.valueOf(newPwd2.getPassword());
+      if (username.isEmpty() || old.isEmpty() || n1.isEmpty() || n2.isEmpty()) {
+        showError("请填写完整信息");
+        return;
+      }
+      if (!n1.equals(n2)) {
+        showError("两次新密码不一致");
+        return;
+      }
+      if (!controller.isValidPassword(n1)) {
+        showError("新密码不符合要求：6-10位，含大小写字母和数字");
+        return;
+      }
+      boolean ok = controller.changePassword(username, old, n1);
+      if (ok) {
+        JOptionPane.showMessageDialog(this, "密码修改成功，请使用新密码登录");
+        cardLayout.show(cards, CARD_LOGIN);
+      } else {
+        showError("修改失败：原密码错误或未完成注册");
+      }
+    });
+
+    backBtn.addActionListener(e -> cardLayout.show(cards, CARD_LOGIN));
+    return panel;
+  }
+
+  private JPanel buildSelectPanel() {
+    JPanel panel = new JPanel(new GridBagLayout());
+    panel.setBorder(BorderFactory.createEmptyBorder(24, 24, 24, 24));
+    GridBagConstraints gc = baseGbc();
+
+    JLabel title = new JLabel("选择难度与题目数量");
+    title.setFont(title.getFont().deriveFont(18f));
+    gc.gridwidth = 2;
+    panel.add(title, gc);
+
+    gc.gridy++;
+    gc.gridwidth = 1;
+    panel.add(new JLabel("难度:"), gc);
+    JComboBox<DifficultyLevel> levelBox = new JComboBox<>(DifficultyLevel.values());
+    gc.gridx = 1;
+    panel.add(levelBox, gc);
+
+    gc.gridy++;
+    gc.gridx = 0;
+    panel.add(new JLabel("题目数量 (10-30):"), gc);
+    JSpinner countSpinner = new JSpinner(new SpinnerNumberModel(10, 10, 30, 1));
+    gc.gridx = 1;
+    panel.add(countSpinner, gc);
+
+    gc.gridy++;
+    gc.gridx = 0;
+    JButton startBtn = new JButton("开始做题");
+    panel.add(startBtn, gc);
+    gc.gridx = 1;
+    JButton logoutBtn = new JButton("退出登录");
+    panel.add(logoutBtn, gc);
+
+    startBtn.addActionListener(e -> {
+      if (currentUsername == null || currentUsername.isEmpty()) {
+        showError("请先登录");
+        cardLayout.show(cards, CARD_LOGIN);
+        return;
+      }
+      DifficultyLevel level = (DifficultyLevel) levelBox.getSelectedItem();
+      int count = (Integer) countSpinner.getValue();
+      try {
+        currentExamSession = controller.createExamSession(currentUsername, level, count);
+        currentSelectedAnswerIndex = -1;
+        loadExamQuestionIntoUI();
+        cardLayout.show(cards, CARD_EXAM);
+      } catch (IllegalArgumentException ex) {
+        showError("无法创建考试：" + ex.getMessage());
+      }
+    });
+
+    logoutBtn.addActionListener(e -> {
+      currentUsername = "";
+      cardLayout.show(cards, CARD_LOGIN);
+    });
+    return panel;
+  }
+
+  private JPanel buildExamPanel() {
+    JPanel panel = new JPanel(new GridBagLayout());
+    panel.setBorder(BorderFactory.createEmptyBorder(24, 24, 24, 24));
+    GridBagConstraints gc = baseGbc();
+
+    JLabel title = new JLabel("答题");
+    title.setFont(title.getFont().deriveFont(18f));
+    gc.gridwidth = 2;
+    panel.add(title, gc);
+
+    gc.gridy++;
+    gc.gridwidth = 2;
+    JTextArea questionArea = new JTextArea(5, 50);
+    questionArea.setEditable(false);
+    questionArea.setLineWrap(true);
+    questionArea.setWrapStyleWord(true);
+    panel.add(new JScrollPane(questionArea), gc);
+
+    gc.gridy++;
+    gc.gridwidth = 2;
+    JPanel optionsPanel = new JPanel(new GridBagLayout());
+    optionsPanel.setBorder(BorderFactory.createEmptyBorder(8, 8, 8, 8));
+    panel.add(optionsPanel, gc);
+
+    ButtonGroup group = new ButtonGroup();
+    JRadioButton[] optionButtons = new JRadioButton[4];
+    for (int i = 0; i < optionButtons.length; i++) {
+      optionButtons[i] = new JRadioButton();
+      group.add(optionButtons[i]);
+    }
+
+    // place options
+    for (int i = 0; i < optionButtons.length; i++) {
+      GridBagConstraints og = new GridBagConstraints();
+      og.gridx = 0;
+      og.gridy = i;
+      og.anchor = GridBagConstraints.WEST;
+      og.insets = new Insets(6, 6, 6, 6);
+      optionsPanel.add(optionButtons[i], og);
+    }
+
+    gc.gridy++;
+    gc.gridwidth = 1;
+    JButton submitBtn = new JButton("提交/下一题");
+    panel.add(submitBtn, gc);
+    gc.gridx = 1;
+    JButton backToSelect = new JButton("中止并返回");
+    panel.add(backToSelect, gc);
+
+    submitBtn.addActionListener(e -> {
+      if (currentExamSession == null) {
+        showError("没有正在进行的考试");
+        return;
+      }
+      int selected = currentSelectedAnswerIndex;
+      if (selected < 0) {
+        showError("请先选择一个选项");
+        return;
+      }
+      try {
+        currentExamSession.setAnswer(selected);
+      } catch (RuntimeException ex) {
+        showError("设置答案失败：" + ex.getMessage());
+        return;
+      }
+      boolean hasNext = currentExamSession.goToNextQuestion();
+      if (hasNext) {
+        currentSelectedAnswerIndex = -1;
+        group.clearSelection();
+        loadExamQuestionIntoUI(questionArea, optionButtons);
+      } else {
+        showScoreAndSave();
+        cardLayout.show(cards, CARD_SCORE);
+      }
+    });
+
+    backToSelect.addActionListener(e -> cardLayout.show(cards, CARD_SELECT));
+
+    // initial load hookup via helper method when starting exam
+    panel.putClientProperty("questionArea", questionArea);
+    panel.putClientProperty("optionButtons", optionButtons);
+    return panel;
+  }
+
+  private JPanel buildScorePanel() {
+    JPanel panel = new JPanel(new GridBagLayout());
+    panel.setBorder(BorderFactory.createEmptyBorder(24, 24, 24, 24));
+    GridBagConstraints gc = baseGbc();
+
+    JLabel title = new JLabel("成绩");
+    title.setFont(title.getFont().deriveFont(18f));
+    gc.gridwidth = 2;
+    panel.add(title, gc);
+
+    gc.gridy++;
+    gc.gridwidth = 2;
+    JLabel scoreLabel = new JLabel("得分: 0.00%");
+    panel.add(scoreLabel, gc);
+
+    gc.gridy++;
+    gc.gridwidth = 1;
+    JButton continueBtn = new JButton("继续做题");
+    panel.add(continueBtn, gc);
+    gc.gridx = 1;
+    JButton exitBtn = new JButton("退出到登录");
+    panel.add(exitBtn, gc);
+
+    continueBtn.addActionListener(e -> cardLayout.show(cards, CARD_SELECT));
+    exitBtn.addActionListener(e -> {
+      currentUsername = "";
+      cardLayout.show(cards, CARD_LOGIN);
+    });
+
+    panel.putClientProperty("scoreLabel", scoreLabel);
+    return panel;
+  }
+
+  private void loadExamQuestionIntoUI() {
+    JPanel examPanel = (JPanel) cards.getComponent(6); // CARD_EXAM position in add order
+    JTextArea questionArea = (JTextArea) examPanel.getClientProperty("questionArea");
+    @SuppressWarnings("unchecked")
+    JRadioButton[] optionButtons = (JRadioButton[]) examPanel.getClientProperty("optionButtons");
+    loadExamQuestionIntoUI(questionArea, optionButtons);
+  }
+
+  private void loadExamQuestionIntoUI(JTextArea questionArea, JRadioButton[] optionButtons) {
+    if (currentExamSession == null) {
+      return;
+    }
+    QuizQuestion question = currentExamSession.getCurrentQuestion();
+    questionArea.setText(question.getQuestionText());
+    List<String> options = question.getOptions();
+    for (int i = 0; i < optionButtons.length; i++) {
+      if (i < options.size()) {
+        optionButtons[i].setText(options.get(i));
+        int idx = i;
+        for (var al : optionButtons[i].getActionListeners()) {
+          optionButtons[i].removeActionListener(al);
+        }
+        optionButtons[i].addActionListener(e -> currentSelectedAnswerIndex = idx);
+        optionButtons[i].setVisible(true);
+      } else {
+        optionButtons[i].setVisible(false);
+      }
+    }
+  }
+
+  private void showScoreAndSave() {
+    if (currentExamSession == null) {
+      return;
+    }
+    double score = currentExamSession.calculateScore();
+    try {
+      controller.saveExamResults(currentExamSession);
+      JOptionPane.showMessageDialog(this,
+          String.format("本次得分：%.2f%%\n结果已保存。", score));
+    } catch (RuntimeException ex) {
+      JOptionPane.showMessageDialog(this,
+          String.format("本次得分：%.2f%%\n保存结果失败：%s", score, ex.getMessage()));
+    }
+    JPanel scorePanel = (JPanel) cards.getComponent(7); // CARD_SCORE
+    JLabel scoreLabel = (JLabel) scorePanel.getClientProperty("scoreLabel");
+    scoreLabel.setText(String.format("得分: %.2f%%", score));
+  }
+
+  private static GridBagConstraints baseGbc() {
+    GridBagConstraints gc = new GridBagConstraints();
+    gc.gridx = 0;
+    gc.gridy = 0;
+    gc.insets = new Insets(8, 8, 8, 8);
+    gc.anchor = GridBagConstraints.WEST;
+    return gc;
+  }
+
+  private void showError(String message) {
+    JOptionPane.showMessageDialog(this, message, "错误", JOptionPane.ERROR_MESSAGE);
+  }
+
+  public static void main(String[] args) {
+    EventQueue.invokeLater(() -> {
+      DesktopApp app = new DesktopApp();
+      app.setLocationRelativeTo(null);
+      app.setVisible(true);
+    });
+  }
+}
+
+