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,
+      )));
+    }
   }
 }

lib/state/app/modules/files/dataProvider/files_data_provider.dart

@@ -1,5 +1,3 @@
-import 'dart:async';
-
 import 'package:nextcloud/nextcloud.dart';
 
 import '../../../../../api/marianumcloud/webdav/queries/listFiles/listFilesCache.dart';
@@ -7,15 +5,30 @@ import '../../../../../api/marianumcloud/webdav/queries/listFiles/listFilesRespo
 import '../../../../../api/marianumcloud/webdav/webdavApi.dart';
 
 class FilesDataProvider {
-  Future<ListFilesResponse> listFiles(String path) {
-    final completer = Completer<ListFilesResponse>();
-    ListFilesCache(
+  /// Lists files at [path]. Cached payload is delivered via [onCacheData] as
+  /// soon as it is read from disk, so callers can render stale data while the
+  /// network call is still pending. The Future itself resolves once both the
+  /// cache lookup and the network attempt have settled, throwing if no payload
+  /// could be obtained at all.
+  Future<ListFilesResponse> listFiles(
+    String path, {
+    void Function(ListFilesResponse)? onCacheData,
+    void Function(Object)? onError,
+  }) async {
+    ListFilesResponse? latest;
+    Object? capturedError;
+    final cache = ListFilesCache(
       path: path,
-      onUpdate: (data) {
-        if (!completer.isCompleted) completer.complete(data);
+      onUpdate: (data) => latest = data,
+      onCacheData: onCacheData,
+      onError: (e) {
+        capturedError = e;
+        onError?.call(e);
       },
     );
-    return completer.future;
+    await cache.ready;
+    if (latest != null) return latest!;
+    throw capturedError ?? Exception('No data and no error from listFiles');
   }
 
   Future<void> createFolder(String fullPath) async {