Cache collectionFileCount to avoid UI flicker post heroAnimation

lib/services/collections_service.dart

@@ -58,6 +58,7 @@ class CollectionsService {
   Future<Map<int, int>>? _collectionIDToNewestFileTime;
   Collection? cachedUncategorizedCollection;
   final Map<String, File> _coverCache = <String, File>{};
+  final Map<int, int> _countCache = <int, int>{};
 
   CollectionsService._privateConstructor() {
     _db = CollectionsDB.instance;
@@ -83,6 +84,7 @@ class CollectionsService {
         _coverCache.removeWhere(
           (key, value) => key.startsWith(event.collectionID!.toString()),
         );
+        _countCache.remove(event.collectionID);
       }
     });
   }
@@ -252,6 +254,20 @@ class CollectionsService {
     return null;
   }
 
+  Future<int> getFileCount(Collection c) async {
+    if (_countCache.containsKey(c.id)) {
+      return _countCache[c.id]!;
+    } else {
+      final count = await _filesDB.collectionFileCount(c.id);
+      _countCache[c.id] = count;
+      return count;
+    }
+  }
+
+  int? getCachedFileCount(Collection c) {
+    return _countCache[c.id];
+  }
+
   Future<bool> setCollectionSyncTime(int collectionID, int? time) async {
     final key = _collectionSyncTimeKeyPrefix + collectionID.toString();
     if (time == null) {

lib/ui/collections/album/column_item.dart

@@ -65,9 +65,8 @@ class AlbumColumnItemWidget extends StatelessWidget {
                     children: [
                       Text(collection.displayName),
                       FutureBuilder<int>(
-                        future: FilesDB.instance.collectionFileCount(
-                          collection.id,
-                        ),
+                        future: CollectionsService.instance.getFileCount
+                          (collection),
                         builder: (context, snapshot) {
                           if (snapshot.hasData) {
                             return Text(

lib/ui/collections/album/row_item.dart

@@ -128,12 +128,21 @@ class AlbumRowItemWidget extends StatelessWidget {
               width: sideOfThumbnail,
               child: FutureBuilder<int>(
                 future: showFileCount
-                    ? FilesDB.instance.collectionFileCount(c.id)
+                    ? CollectionsService.instance.getFileCount(c)
                     : Future.value(0),
                 builder: (context, snapshot) {
-                  if (snapshot.hasData && snapshot.data! > 0) {
+                  int? cachedCount;
+                  if (showFileCount) {
+                    if (snapshot.hasData) {
+                      cachedCount = snapshot.data;
+                    } else {
+                      cachedCount =
+                          CollectionsService.instance.getCachedFileCount(c);
+                    }
+                  }
+                  if (cachedCount != null && cachedCount > 0) {
                     final String textCount =
-                        NumberFormat().format(snapshot.data);
+                        NumberFormat().format(cachedCount);
                     return Row(
                       children: [
                         Container(