better loading indicators for timetables, talk and files

lib/state/app/modules/files/bloc/files_bloc.dart

@@ -1,3 +1,5 @@
+import '../../../../../api/marianumcloud/webdav/queries/listFiles/listFilesResponse.dart';
+import '../../../infrastructure/loadableState/loading_error.dart';
 import '../../../infrastructure/utilityWidgets/loadableHydratedBloc/loadable_hydrated_bloc.dart';
 import '../../../infrastructure/utilityWidgets/loadableHydratedBloc/loadable_hydrated_bloc_event.dart';
 import '../repository/files_repository.dart';
@@ -28,12 +30,14 @@ class FilesBloc extends LoadableHydratedBloc<FilesEvent, FilesState, FilesReposi
   }
 
   Future<void> refresh() async {
+    add(RefetchStarted<FilesState>());
     final path = innerState?.currentPath ?? initialPath;
     await _query(path);
   }
 
   Future<void> setPath(List<String> path) async {
     add(Emit((s) => s.copyWith(currentPath: path, listing: null)));
+    add(RefetchStarted<FilesState>());
     await _query(path);
   }
 
@@ -45,8 +49,34 @@ class FilesBloc extends LoadableHydratedBloc<FilesEvent, FilesState, FilesReposi
 
   Future<void> _query(List<String> path) async {
     final pathString = path.isEmpty ? '/' : path.join('/');
-    final listing = await repo.data.listFiles(pathString);
-    listing.files.removeWhere((file) => file.name.isEmpty || file.name == path.lastOrNull);
-    add(DataGathered((s) => s.copyWith(listing: listing)));
+
+    Object? capturedError;
+    ListFilesResponse? listing;
+    try {
+      listing = await repo.data.listFiles(
+        pathString,
+        onCacheData: (cached) {
+          // Cached payload arrives before the network call settles. Surface it
+          // immediately via Emit so the listing is visible while isLoading
+          // stays true and the top loading bar keeps spinning.
+          cached.files.removeWhere((file) => file.name.isEmpty || file.name == path.lastOrNull);
+          add(Emit((s) => s.copyWith(listing: cached)));
+        },
+        onError: (e) => capturedError = e,
+      );
+    } catch (e) {
+      capturedError = e;
+    }
+
+    if (listing != null) {
+      listing.files.removeWhere((file) => file.name.isEmpty || file.name == path.lastOrNull);
+      add(DataGathered((s) => s.copyWith(listing: listing)));
+    }
+    if (capturedError != null) {
+      add(Error(LoadingError(
+        message: capturedError.toString(),
+        allowRetry: true,
+      )));
+    }
   }
 }