small change

SpineViewer/Exporter/Implementations/Exporter/FrameSequenceExporter.cs

@@ -20,13 +20,14 @@ namespace SpineViewer.Exporter.Implementations.Exporter
         protected override void ExportSingle(Spine.Spine[] spinesToRender, BackgroundWorker? worker = null)
         {
             var args = (FrameSequenceExportArgs)ExportArgs;
-            int frameIdx = 0;
-            foreach (var frame in GetFrames(spinesToRender, worker))
-            {
+
             // 导出单个时必定提供输出文件夹, 
             var saveDir = Path.Combine(args.OutputDir, $"frames_{timestamp}_{args.FPS:f0}");
             Directory.CreateDirectory(saveDir);
 
+            int frameIdx = 0;
+            foreach (var frame in GetFrames(spinesToRender, worker))
+            {
                 var filename = $"frames_{timestamp}_{args.FPS:f0}_{frameIdx:d6}{args.FileSuffix}";
                 var savePath = Path.Combine(saveDir, filename);