fix: Android/iOS scrolling UI adjustment

Pixiview/Illust/IllustCollectionPage.cs

@@ -23,8 +23,7 @@ namespace Pixiview.Illust
     }
     public abstract class IllustCollectionPage<T> : AdaptedPage, IIllustCollectionPage
     {
-        protected static readonly Thickness normalMargin = new Thickness(16);
+        protected const double loadingOffset = -40;
-        protected static readonly Thickness loadingMargin = new Thickness(16, 46, 0, 0);
 
         #region - Properties -
 
@@ -94,7 +93,7 @@ namespace Pixiview.Illust
 
         public override void OnUnload()
         {
-            Illusts = IllustCollection.Empty;
+            Illusts = null;
             lastUpdated = default;
         }
 
@@ -179,41 +178,10 @@ namespace Pixiview.Illust
             var page = new ViewIllustPage(illust, IsFavoriteVisible);
             Navigation.PushAsync(page);
         }
-        protected virtual void DoIllustsLoaded(IllustCollection collection, bool bottom)
+        protected virtual IllustCollection GetIllustsLoadedCollection(IllustCollection collection, bool bottom)
         {
             IllustCollection = collection;
-            var indicator = LoadingIndicator;
+            return collection;
-            if (indicator == null)
-            {
-                Illusts = collection;
-                IsLoading = false;
-                IsBottomLoading = false;
-            }
-            else
-            {
-                var offset = 16 - IndicatorMarginTop;
-                indicator.Animate("margin", top =>
-                {
-                    indicator.Margin = new Thickness(0, top, 0, offset);
-                },
-                16 - offset, -40 - offset, easing: Easing.CubicIn, finished: (v, r) =>
-                {
-                    IsLoading = false;
-                    IsBottomLoading = false;
-                    if (IsDelayLoading)
-                    {
-                        Device.StartTimer(TimeSpan.FromMilliseconds(250), () =>
-                        {
-                            Illusts = collection;
-                            return false;
-                        });
-                    }
-                    else
-                    {
-                        Illusts = collection;
-                    }
-                });
-            }
         }
 
         protected virtual void StartLoad(bool force = false, bool isBottom = false)
@@ -233,16 +201,20 @@ namespace Pixiview.Illust
                     {
                         IsLoading = true;
                     }
-                    Device.StartTimer(TimeSpan.FromMilliseconds(250), () =>
+#if __IOS__
+                    Task.Run(() => DoLoadIllusts(force, isBottom));
+#else
+                    Device.StartTimer(TimeSpan.FromMilliseconds(150), () =>
                     {
                         Task.Run(() => DoLoadIllusts(force, isBottom));
                         return false;
                     });
+#endif
                 }
                 else
                 {
                     var offset = 16 - IndicatorMarginTop;
-                    indicator.Margin = new Thickness(0, -40 - offset, 0, offset);
+                    indicator.Margin = new Thickness(0, loadingOffset - offset, 0, offset);
                     if (isBottom)
                     {
                         IsBottomLoading = true;
@@ -255,7 +227,7 @@ namespace Pixiview.Illust
                     {
                         indicator.Margin = new Thickness(0, top, 0, offset);
                     },
-                    -40 - offset, 16 - offset, easing: Easing.CubicOut, finished: (v, r) =>
+                    loadingOffset - offset, 16 - offset, easing: Easing.CubicOut, finished: (v, r) =>
                     {
                         Task.Run(() => DoLoadIllusts(force, isBottom));
                     });
@@ -263,6 +235,52 @@ namespace Pixiview.Illust
             }
         }
 
+        protected virtual void DoIllustsLoaded(IllustCollection collection, bool bottom)
+        {
+            collection = GetIllustsLoadedCollection(collection, bottom);
+
+            var indicator = LoadingIndicator;
+            if (indicator == null || bottom)
+            {
+                Illusts = collection;
+                IsLoading = false;
+                IsBottomLoading = false;
+            }
+            else
+            {
+                var offset = 16 - IndicatorMarginTop;
+                indicator.Animate("margin", top =>
+                {
+                    indicator.Margin = new Thickness(0, top, 0, offset);
+                },
+                16 - offset, loadingOffset - offset, easing: Easing.CubicIn, finished: (v, r) =>
+                {
+                    IsLoading = false;
+                    IsBottomLoading = false;
+#if __IOS__
+                    if (IsDelayLoading)
+                    {
+                        Device.StartTimer(TimeSpan.FromMilliseconds(250), () =>
+                        {
+                            Illusts = collection;
+                            return false;
+                        });
+                    }
+                    else
+                    {
+                        Illusts = collection;
+                    }
+#else
+                    Device.StartTimer(TimeSpan.FromMilliseconds(150), () =>
+                    {
+                        Illusts = collection;
+                        return false;
+                    });
+#endif
+                });
+            }
+        }
+
         protected DataTemplate GetCardViewTemplate(bool hideUser = false)
         {
             return new DataTemplate(() =>
@@ -589,7 +607,7 @@ namespace Pixiview.Illust
             base.StartLoad(force, isBottom);
         }
 
-        protected override void DoIllustsLoaded(IllustCollection collection, bool bottom)
+        protected override IllustCollection GetIllustsLoadedCollection(IllustCollection collection, bool bottom)
         {
             var now = IllustCollection;
             if (now == null)
@@ -600,29 +618,7 @@ namespace Pixiview.Illust
             {
                 now = new IllustCollection(now.Concat(collection));
             }
-            IllustCollection = now;
+            return now;
-
-            var indicator = LoadingIndicator;
-            if (indicator == null)
-            {
-                Illusts = now;
-                IsLoading = false;
-                IsBottomLoading = false;
-            }
-            else
-            {
-                var offset = 16 - IndicatorMarginTop;
-                indicator.Animate("margin", top =>
-                {
-                    indicator.Margin = new Thickness(0, top, 0, offset);
-                },
-                16 - offset, -40 - offset, easing: Easing.CubicIn, finished: (v, r) =>
-                {
-                    IsLoading = false;
-                    IsBottomLoading = false;
-                    Illusts = now;
-                });
-            }
         }
 
         protected void OnScrolled(double y)

Pixiview/Illust/RecommendsPage.xaml.cs

@@ -49,6 +49,12 @@ namespace Pixiview.Illust
 
         protected override ActivityIndicator LoadingIndicator => activityLoading;
 
+        public override void OnUnload()
+        {
+            base.OnUnload();
+            Users = null;
+        }
+
         private void OnIllustUserItemTapped(IllustUserItem item)
         {
             Start(async () =>
@@ -279,8 +285,17 @@ namespace Pixiview.Illust
             {
                 IsLoading = false;
                 UserRecommendsVisible = list.Count > 0;
+#if __IOS__
                 Users = list;
                 Illusts = IllustCollection;
+#else
+                Device.StartTimer(TimeSpan.FromMilliseconds(150), () =>
+                {
+                    Users = list;
+                    Illusts = IllustCollection;
+                    return false;
+                });
+#endif
             });
 
             DoLoadUserRecommendsImages(list);

Pixiview/UI/FlowLayout.cs

@@ -140,7 +140,13 @@ namespace Pixiview.UI
             {
                 oldNotify.CollectionChanged -= flowLayout.OnCollectionChanged;
             }
-            if (newValue is IList newList)
+            if (newValue == null)
+            {
+                flowLayout.Children.Clear();
+                //flowLayout.UpdateChildrenLayout();
+                //flowLayout.InvalidateLayout();
+            }
+            else if (newValue is IList newList)
             {
                 flowLayout.Children.Clear();
                 for (var i = 0; i < newList.Count; i++)