Make snackbar appear when state changes in BLoC

lib/food_entry/food_entry_bloc.dart

@@ -47,6 +47,12 @@ class FoodEntryBloc extends Bloc<FoodEvent, PageState> {
     if (scanResult.type == ResultType.Cancelled) {
       return;
     }
+    if (scanResult.type == ResultType.Error) {
+      emit(PageState(
+          foodEntries: state.foodEntries,
+          errorString: "Fehler beim Scannen des Barcodes"));
+      return;
+    }
     var responseFuture = client.retrieveFoodInfo(scanResult.rawContent);
 
     List<FoodEntryState> newList = List.from(state.foodEntries);
@@ -58,6 +64,20 @@ class FoodEntryBloc extends Bloc<FoodEvent, PageState> {
     await responseFuture.then((response) {
       newList.removeWhere((entryState) => entryState.id == newEntryWaiting.id);
 
+      if (response.status == FoodFactResponseStatus.barcodeNotFound) {
+        emit(PageState(
+            foodEntries: state.foodEntries,
+            errorString: "Barcode konnte nicht gefunden werden."));
+        return;
+      }
+      if (response.status ==
+          FoodFactResponseStatus.foodFactServerNotReachable) {
+        emit(PageState(
+            foodEntries: state.foodEntries,
+            errorString: "OpenFoodFacts-Server konnte nicht erreicht werden."));
+        return;
+      }
+
       var newEntryFinishedWaiting = FoodEntryState(
         name: response.food?.name ?? "",
         mass: response.food?.mass ?? 0,
@@ -93,8 +113,9 @@ class BarcodeScanned extends FoodEvent {
 /// This is the state for one date/page
 class PageState {
   final List<FoodEntryState> foodEntries;
+  final String? errorString;
 
-  PageState({required this.foodEntries});
+  PageState({required this.foodEntries, this.errorString});
 
   factory PageState.init() {
     return PageState(foodEntries: []);

lib/perdate/perdate_widget.dart

@@ -56,19 +56,24 @@ class _PerDateWidgetState extends State<PerDateWidget> {
                       ),
                     )
                   ],
-                  child: BlocBuilder<FoodEntryBloc, PageState>(
+                  child: BlocConsumer<FoodEntryBloc, PageState>(
-                      builder: (context, state) {
+                      listener: (context, pageState) {
+                    if (pageState.errorString != null) {
+                      showNewSnackbarWith(context, pageState.errorString!);
+                    }
+                  }, builder: (context, pageState) {
                     return Scaffold(
                         appBar: AppBar(
                           title:
                               Text(DateFormat.yMMMMd('de').format(widget.date)),
                           actions: const [ThemeSwitcherButton()],
                         ),
-                        body: FoodEntryList(entries: state.foodEntries),
+                        body: FoodEntryList(entries: pageState.foodEntries),
                         bottomNavigationBar: BottomAppBar(
                             shape: const RectangularNotchShape(),
                             color: Theme.of(context).colorScheme.secondary,
-                            child: SumWidget(foodEntries: state.foodEntries)),
+                            child:
+                                SumWidget(foodEntries: pageState.foodEntries)),
                         drawer: const AppDrawer(),
                         floatingActionButton: OverflowBar(children: [
                           ScanFoodFloatingButton(