src/controller/AppController.java

@@ -104,4 +104,8 @@ public class AppController {
             JOptionPane.showMessageDialog(frame, "请输入有效的数字！");
         }
     }
+
+    public UserManager getUserManager() {
+        return userManager;
+    }
 }

src/controller/UserManager.java

@@ -25,6 +25,14 @@ public class UserManager {
         return users.containsKey(email);
     }
 
+    public boolean isUsernameExists(String username) {
+        for (User user : users.values()) {
+            if (user.getUsername().equalsIgnoreCase(username)) {
+                return true;
+            }
+        }
+        return false;
+    }
     // 修改 addUser 方法，接收 username 参数
     public void addUser(String email, String password, String username) {
         users.put(email, new User(email, password, username));

src/ui/RegisterPanel.java

@@ -1,6 +1,7 @@
 package ui;
 
 import controller.AppController;
+import controller.UserManager;
 import util.EmailUtil;
 
 import javax.swing.*;
@@ -109,7 +110,15 @@ public class RegisterPanel extends JPanel {
                 JOptionPane.showMessageDialog(this, "密码需包含大小写字母与数字，长度6-10位！");
                 return;
             }
-
+            //防止用户名重复
+            if (controller.getUserManager().isUsernameExists(username)) {
+                JOptionPane.showMessageDialog(this, "用户名已存在，请更换！");
+                return;
+            }
+            if (username.isEmpty() || password.isEmpty() || email.isEmpty() || code.isEmpty()) {
+                JOptionPane.showMessageDialog(this, "请填写完整信息！");
+                return;
+            }
             controller.handleRegister(email, password, username); // 传递username
         });