Added Scroll indicator

Author: Vijay-Nirmal

Microsoft.Toolkit.Uwp.SampleApp/SamplePages/ListViewExtensions/ListViewExtensionsPage.xaml

@@ -35,14 +35,16 @@
         </Grid>
 
         <StackPanel Grid.Column="1" Margin="5,10,10,0" Width="200">
-            <TextBlock Text="Smooth Scroll Settings" FontSize="{StaticResource TextStyleLargeFontSize}" Margin="0,0,0,10"/>
+            <TextBlock Text="Smooth Scroll Settings" FontSize="{StaticResource TextStyleLargeFontSize}"/>
             <TextBox x:Name="IndexInput"
                      Header="Index"
                      InputScope="Number"
-                     Text="100" />
+                     Text="100"
+                     Margin="0,10,0,0" />
             <ComboBox x:Name="ItemPlacementInput"
                       Header="Item Placement"
-                      SelectedIndex="0">
+                      SelectedIndex="0"
+                      Margin="0,10,0,0" >
                 <x:String>Default</x:String>
                 <x:String>Left</x:String>
                 <x:String>Top</x:String>
@@ -52,18 +54,25 @@
             </ComboBox>
             <CheckBox x:Name="DisableAnimationInput"
                       Content="Disable Animation"
-                      IsChecked="False" />
+                      IsChecked="False"
+                      Margin="0,10,0,0" />
             <CheckBox x:Name="ScrollIfVisibileInput"
                       Content="Scroll If Visible"
                       IsChecked="True" />
             <TextBox x:Name="AdditionalHorizontalOffsetInput"
                      Header="Horizontal Offset"
                      InputScope="Number"
-                     Text="0" />
+                     Text="0"
+                     Margin="0,10,0,0" />
             <TextBox x:Name="AdditionalVerticalOffsetInput"
                      Header="Vertical Offset"
                      InputScope="Number"
-                     Text="0" />
+                     Text="0"
+                     Margin="0,10,0,0" />
+            <StackPanel Orientation="Horizontal" Margin="0,10,0,0">
+                <Ellipse x:Name="ScrollIndicator" Fill="Red" Width="15" Height="15"/>
+                <TextBlock x:Name="ScrollIndicatorTest" Text="Scroll not started" Margin="10,0,0,0"/>
+            </StackPanel>
         </StackPanel>
     </Grid>
 </Page>

Microsoft.Toolkit.Uwp.SampleApp/SamplePages/ListViewExtensions/ListViewExtensionsPage.xaml.cs

@@ -6,9 +6,11 @@
 using System.Collections.ObjectModel;
 using System.Windows.Input;
 using Microsoft.Toolkit.Uwp.UI;
+using Windows.UI;
 using Windows.UI.Popups;
 using Windows.UI.Xaml;
 using Windows.UI.Xaml.Controls;
+using Windows.UI.Xaml.Media;
 
 namespace Microsoft.Toolkit.Uwp.SampleApp.SamplePages
 {
@@ -55,7 +57,9 @@ private void Load()
                 var scrollIfVisibile = ScrollIfVisibileInput.IsChecked ?? true;
                 var additionalHorizontalOffset = int.TryParse(AdditionalHorizontalOffsetInput.Text, out var ho) ? ho : 0;
                 var additionalVerticalOffset = int.TryParse(AdditionalVerticalOffsetInput.Text, out var vo) ? vo : 0;
+                UpdateScrollIndicator(true);
                 await sampleListView.SmoothScrollIntoViewWithIndexAsync(index, itemPlacement, disableAnimation, scrollIfVisibile, additionalHorizontalOffset, additionalVerticalOffset);
+                UpdateScrollIndicator(false);
             });
 
             if (sampleListView != null)
@@ -64,6 +68,20 @@ private void Load()
             }
         }
 
+        private void UpdateScrollIndicator(bool isScrolling)
+        {
+            if (isScrolling)
+            {
+                ScrollIndicatorTest.Text = "Scroll started";
+                ScrollIndicator.Fill = new SolidColorBrush(Colors.Green);
+            }
+            else
+            {
+                ScrollIndicator.Fill = new SolidColorBrush(Colors.Red);
+                ScrollIndicatorTest.Text = "Scroll completed";
+            }
+        }
+
         private ObservableCollection<string> GetOddEvenSource(int count)
         {
             var oddEvenSource = new ObservableCollection<string>();

Microsoft.Toolkit.Uwp.UI/Extensions/ListViewBase/ListViewExtensions.SmoothScrollIntoView.cs

@@ -201,6 +201,12 @@ public static async Task SmoothScrollIntoViewWithItemAsync(this ListViewBase lis
         /// <param name="disableAnimation">if set to <c>true</c> disable animation.</param>
         private static async Task ChangeViewAsync(this ScrollViewer scrollViewer, double? horizontalOffset, double? verticalOffset, float? zoomFactor, bool disableAnimation)
         {
+            // MUST check this an return immediately, otherwise this async task will never completes because ViewChanged event won't triggered
+            if (horizontalOffset == scrollViewer.HorizontalOffset && verticalOffset == scrollViewer.VerticalOffset)
+            {
+                return;
+            }
+
             var tcs = new TaskCompletionSource<object>();
 
             void ViewChanged(object _, ScrollViewerViewChangedEventArgs e)