Show a notification when the user has no notification to show

lib/ui/screens/notifications_screen.dart

@@ -42,6 +42,8 @@ class _NotificationsScreenState extends State<NotificationsScreen> {
         _users = users;
         _groups = groups;
       });
+
+      setStatus(_Status.NONE);
     } on Exception catch (e) {
       print("Exception while getting the list of notifications!");
       print(e);
@@ -59,6 +61,28 @@ class _NotificationsScreenState extends State<NotificationsScreen> {
 
   @override
   Widget build(BuildContext context) {
+    // Loading status
+    if (_list == null || _status == _Status.LOADING)
+      return Center(
+        child: CircularProgressIndicator(),
+      );
+
+    return Column(
+      children: [
+        Expanded(
+          child: RefreshIndicator(
+              child: SingleChildScrollView(
+                physics: AlwaysScrollableScrollPhysics(),
+                child: _buildBody(),
+              ),
+              onRefresh: _loadList),
+        )
+      ],
+    );
+  }
+
+  /// Build body
+  Widget _buildBody() {
     // In case of error
     if (_status == _Status.ERROR)
       return buildErrorCard(tr("Could not get the list of notifications!"),
@@ -69,10 +93,13 @@ class _NotificationsScreenState extends State<NotificationsScreen> {
             )
           ]);
 
-    // Loading status
-    if (_list == null || _status == _Status.LOADING)
-      return Center(
-        child: CircularProgressIndicator(),
+    // When there is no notification
+    if (_list.length == 0)
+      return Padding(
+        padding: const EdgeInsets.all(8.0),
+        child: Center(
+          child: Text(tr("You do not have any notification now.")),
+        ),
       );
   }
 }