Merge pull request #2813 from AvaloniaUI/fixes/2804-itemsrepeater-problems

Fix ItemsRepeater problems

samples/ControlCatalog/Pages/ItemsRepeaterPage.xaml

@@ -6,19 +6,20 @@
       <TextBlock Classes="h1">ItemsRepeater</TextBlock>
       <TextBlock Classes="h2">A data-driven collection control that incorporates a flexible layout system, custom views, and virtualization.</TextBlock>
     </StackPanel>
-    <StackPanel DockPanel.Dock="Right" Margin="8 0">
+    <StackPanel DockPanel.Dock="Right" Margin="8 0" Spacing="4">
       <ComboBox SelectedIndex="0" SelectionChanged="LayoutChanged">
         <ComboBoxItem>Stack - Vertical</ComboBoxItem>
         <ComboBoxItem>Stack - Horizontal</ComboBoxItem>
         <ComboBoxItem>UniformGrid - Vertical</ComboBoxItem>
         <ComboBoxItem>UniformGrid - Horizontal</ComboBoxItem>
       </ComboBox>
+      <Button Command="{Binding AddItem}">Add Item</Button>
     </StackPanel>
     <Border BorderThickness="1" BorderBrush="{DynamicResource ThemeBorderMidBrush}" Margin="0 0 0 16">
       <ScrollViewer Name="scroller"
                     HorizontalScrollBarVisibility="Auto"
                     VerticalScrollBarVisibility="Auto">
-        <ItemsRepeater Name="repeater" Items="{Binding}"/>
+        <ItemsRepeater Name="repeater" Background="Transparent" Items="{Binding Items}"/>
       </ScrollViewer>
     </Border>
   </DockPanel>

samples/ControlCatalog/Pages/ItemsRepeaterPage.xaml.cs

@@ -1,8 +1,11 @@
+using System;
 using System.Linq;
 using Avalonia.Controls;
 using Avalonia.Controls.Primitives;
+using Avalonia.Input;
 using Avalonia.Layout;
 using Avalonia.Markup.Xaml;
+using ControlCatalog.ViewModels;
 
 namespace ControlCatalog.Pages
 {
@@ -16,7 +19,8 @@ namespace ControlCatalog.Pages
             this.InitializeComponent();
             _repeater = this.FindControl<ItemsRepeater>("repeater");
             _scroller = this.FindControl<ScrollViewer>("scroller");
-            DataContext = Enumerable.Range(1, 100000).Select(i => $"Item {i}" ).ToArray();
+            _repeater.PointerPressed += RepeaterClick;
+            DataContext = new ItemsRepeaterPageViewModel();
         }
 
         private void InitializeComponent()
@@ -67,5 +71,11 @@ namespace ControlCatalog.Pages
                     break;
             }
         }
+
+        private void RepeaterClick(object sender, PointerPressedEventArgs e)
+        {
+            var item = (e.Source as TextBlock)?.DataContext as string;
+            ((ItemsRepeaterPageViewModel)DataContext).SelectedItem = item;
+        }
     }
 }

samples/ControlCatalog/ViewModels/ItemsRepeaterPageViewModel.cs

@@ -0,0 +1,27 @@
+using System.Collections.ObjectModel;
+using System.Linq;
+using ReactiveUI;
+
+namespace ControlCatalog.ViewModels
+{
+    public class ItemsRepeaterPageViewModel : ReactiveObject
+    {
+        private int newItemIndex = 1;
+
+        public ItemsRepeaterPageViewModel()
+        {
+            Items = new ObservableCollection<string>(
+                Enumerable.Range(1, 100000).Select(i => $"Item {i}"));
+        }
+
+        public ObservableCollection<string> Items { get; }
+
+        public string SelectedItem { get; set; }
+
+        public void AddItem()
+        {
+            var index = SelectedItem != null ? Items.IndexOf(SelectedItem) : -1;
+            Items.Insert(index + 1, $"New Item {newItemIndex++}");
+        }
+    }
+}

src/Avalonia.Controls/Repeater/ItemsRepeater.cs

@@ -707,9 +707,9 @@ namespace Avalonia.Controls
             }
         }
 
-        private void InvalidateArrangeForLayout(object sender, EventArgs e) => InvalidateMeasure();
+        private void InvalidateMeasureForLayout(object sender, EventArgs e) => InvalidateMeasure();
 
-        private void InvalidateMeasureForLayout(object sender, EventArgs e) => InvalidateArrange();
+        private void InvalidateArrangeForLayout(object sender, EventArgs e) => InvalidateArrange();
 
         private VirtualizingLayoutContext GetLayoutContext()
         {

src/Avalonia.Controls/Repeater/ItemsSourceView.cs

@@ -35,9 +35,11 @@ namespace Avalonia.Controls
         {
             Contract.Requires<ArgumentNullException>(source != null);
 
-            _inner = source as IList;
-
-            if (_inner == null && source is IEnumerable<object> objectEnumerable)
+            if (source is IList list)
+            {
+                _inner = list;
+            }
+            else if (source is IEnumerable<object> objectEnumerable)
             {
                 _inner = new List<object>(objectEnumerable);
             }

src/Avalonia.Layout/UniformGridLayoutState.cs

@@ -72,12 +72,6 @@ namespace Avalonia.Layout
 
                     _cachedFirstElement.Measure(availableSize);
 
-                    // This doesn't need to be done in the UWP version and I'm not sure why. If we
-                    // don't do this here, and we receive a recycled element then it will be shown
-                    // at its previous arrange point, but we don't want it shown at all until its
-                    // arranged.
-                    _cachedFirstElement.Arrange(new Rect(-10000.0, -10000.0, 0, 0));
-
                     SetSize(_cachedFirstElement, layoutItemWidth, LayoutItemHeight, availableSize, stretch, orientation, minRowSpacing, minColumnSpacing);
 
                     // See if we can move ownership to the flow algorithm. If we can, we do not need a local cache.