修复在线设备数量

src/DRS9.Dashboard.Server/Controllers/DevicesManagementController.cs

@@ -342,13 +342,16 @@ public class DashboardController : ControllerBase
 {
     private readonly DeviceManagementService _deviceManagementService;
     private readonly ApplicationService _applicationService;
+    private readonly ILogger<DashboardController> _logger;
 
     public DashboardController(
         DeviceManagementService deviceManagementService,
-        ApplicationService applicationService)
+        ApplicationService applicationService,
+        ILogger<DashboardController> logger)
     {
         _deviceManagementService = deviceManagementService;
         _applicationService = applicationService;
+        _logger = logger;
     }
 
     /// <summary>
@@ -360,10 +363,26 @@ public class DashboardController : ControllerBase
         var devices = await _deviceManagementService.GetAllDevicesAsync();
         var applications = await _applicationService.GetAllAsync();
 
+        // 在线设备：1分钟内有活动
+        var onlineThreshold = DateTime.UtcNow.AddMinutes(-1);
+        var onlineCount = devices.Data.Count(d => d.LastSeenAt.HasValue && d.LastSeenAt >= onlineThreshold);
+
+        // 调试输出
+        _logger.LogInformation("UTC Now: {Now}", DateTime.UtcNow.ToString("yyyy-MM-dd HH:mm:ss"));
+        _logger.LogInformation("Online Threshold: {Threshold}", onlineThreshold.ToString("yyyy-MM-dd HH:mm:ss"));
+        foreach (var d in devices.Data)
+        {
+            _logger.LogInformation("Device {Id}: LastSeenAt={LastSeenAt}, IsOnline={IsOnline}",
+                d.Id,
+                d.LastSeenAt?.ToString("yyyy-MM-dd HH:mm:ss") ?? "null",
+                d.LastSeenAt.HasValue && d.LastSeenAt >= onlineThreshold);
+        }
+        _logger.LogInformation("Online Count: {Count}", onlineCount);
+
         var stats = new DashboardStatsDto
         {
             TotalDevices = devices.Data.Count,
-            OnlineDevices = devices.Data.Count(d => d.IsEnabled),
+            OnlineDevices = onlineCount,
             TotalApplications = applications.Total
         };