fix livequery (#608)

Fix: ParseLiveQueryWidget wont add element to an empty list

Author: fischerscode

packages/flutter/lib/src/utils/parse_live_list.dart

@@ -92,24 +92,20 @@ class _ParseLiveListWidgetState<T extends sdk.ParseObject>
       listeningIncludes: listeningIncludes,
       lazyLoading: lazyLoading,
       preloadedColumns: preloadedColumns,
-    ).then((sdk.ParseLiveList<T> value) {
-      if (value.size > 0) {
-        setState(() {
-          noData = false;
-        });
-      } else {
-        setState(() {
-          noData = true;
-        });
-      }
+    ).then((sdk.ParseLiveList<T> livelist) {
       setState(() {
-        _liveList = value;
+        _noData = livelist.size == 0;
+        _liveList = livelist;
         _liveList!.stream
             .listen((sdk.ParseLiveListEvent<sdk.ParseObject> event) {
           if (event is sdk.ParseLiveListAddEvent) {
-            if (_animatedListKey.currentState != null)
+            if (_animatedListKey.currentState != null) {
               _animatedListKey.currentState!
                   .insertItem(event.index, duration: widget.duration);
+            }
+            setState(() {
+              _noData = livelist.size == 0;
+            });
           } else if (event is sdk.ParseLiveListDeleteEvent) {
             _animatedListKey.currentState!.removeItem(
                 event.index,
@@ -126,15 +122,9 @@ class _ParseLiveListWidgetState<T extends sdk.ParseObject>
                       preLoadedData: () => event.object as T,
                     ),
                 duration: widget.duration);
-            if (value.size > 0) {
-              setState(() {
-                noData = false;
-              });
-            } else {
-              setState(() {
-                noData = true;
-              });
-            }
+            setState(() {
+              _noData = livelist.size == 0;
+            });
           }
         });
       });
@@ -146,17 +136,26 @@ class _ParseLiveListWidgetState<T extends sdk.ParseObject>
   final GlobalKey<AnimatedListState> _animatedListKey =
       GlobalKey<AnimatedListState>();
   final ChildBuilder<T>? removedItemBuilder;
-  bool noData = true;
+  bool _noData = true;
 
   @override
   Widget build(BuildContext context) {
     if (_liveList == null) {
       return widget.listLoadingElement ?? Container();
+    } else {
+      return Stack(
+        children: <Widget>[
+          if (widget.queryEmptyElement != null)
+            AnimatedOpacity(
+              opacity: _noData ? 1 : 0,
+              duration: widget.duration,
+              child: widget.queryEmptyElement,
+            ),
+          //_liveList isn't (checked above)
+          buildAnimatedList(_liveList!),
+        ],
+      );
     }
-    if (noData) {
-      return widget.queryEmptyElement ?? Container();
-    }
-    return buildAnimatedList(_liveList!);
   }
 
   @override