ADD file via upload

src/main/java/com/example/myapp/controller/GradeSelectionController.java

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+package com.example.myapp.controller;
+
+import com.example.myapp.Main;
+import com.example.myapp.service.ExamService;
+import javafx.fxml.FXML;
+import javafx.scene.control.*;
+
+public class GradeSelectionController {
+  @FXML private Label welcomeLabel;
+
+  private String email;
+  private final ExamService examService = ExamService.getInstance();
+
+  public void initUser(String email) {
+    this.email = email;
+    welcomeLabel.setText("欢迎 " + email + "，请选择学段");
+  }
+
+  @FXML
+  public void onPrimarySchoolSelected() {
+    showQuestionCountDialog("小学");
+  }
+
+  @FXML
+  public void onMiddleSchoolSelected() {
+    showQuestionCountDialog("初中");
+  }
+
+  @FXML
+  public void onHighSchoolSelected() {
+    showQuestionCountDialog("高中");
+  }
+
+  @FXML
+  public void onBackToLogin() {
+    try {
+      Main.showLogin();
+    } catch (Exception e) {
+      e.printStackTrace();
+    }
+  }
+
+  @FXML
+  public void onBackToDashboard() {
+    try {
+      Main.showDashboard(email);
+    } catch (Exception e) {
+      e.printStackTrace();
+    }
+  }
+
+  private void showQuestionCountDialog(String gradeLevel) {
+    TextInputDialog dialog = new TextInputDialog("10");
+    dialog.setTitle("题目数量");
+    dialog.setHeaderText("选择" + gradeLevel + "题目");
+    dialog.setContentText("请输入题目数量(1-100):");
+
+    dialog.showAndWait().ifPresent(countStr -> {
+      try {
+        int questionCount = Integer.parseInt(countStr);
+        if (questionCount < 1 || questionCount > 100) {
+          showAlert("题目数量必须在1-100之间");
+          return;
+        }
+
+        boolean success = examService.generateExam(gradeLevel, questionCount, email);
+        if (success) {
+          // 修复：添加异常处理
+          try {
+            Main.showExamPage(email);
+          } catch (Exception e) {
+            e.printStackTrace();
+            showAlert("无法进入考试页面");
+          }
+        } else {
+          showAlert("生成试卷失败，请重试");
+        }
+
+      } catch (NumberFormatException e) {
+        showAlert("请输入有效的数字");
+      }
+    });
+  }
+
+  private void showAlert(String message) {
+    Alert alert = new Alert(Alert.AlertType.ERROR);
+    alert.setTitle("错误");
+    alert.setHeaderText(null);
+    alert.setContentText(message);
+    alert.showAndWait();
+  }
+}