UWP Catch List View Scroll Event

Question

Я разрабатываю Windows Universal App для телефона.

У меня есть вид списка и кнопка над ним. Я хочу скрыть кнопку, когда я прокручу вниз в представлении списка.

Как я могу поймать событие прокрутки? Как я могу получить доступ к ScrollViewer внутри ListView?

Я попробовал несколько способов, но ни один не похоже на работу ..

Мой XAML Кодекс:

<ListView x:Name="PostListView" Grid.Row="1" 
         IsItemClickEnabled="True" 
         ItemTemplate="{StaticResource PostItemTemplate}" 
         ItemsSource="{Binding Feed}" 
         ShowsScrollingPlaceholders="False" 
         ScrollViewer.VerticalScrollBarVisibility="Auto" 
         ScrollViewer.VerticalScrollMode="Enabled" 
         IncrementalLoadingTrigger="Edge"> 
         <ListView.ItemContainerStyle> 
          <Style TargetType="ListViewItem"> 
           <Setter Property="HorizontalContentAlignment" Value="Stretch" /> 
           <Setter Property="Padding" Value="0" /> 
           <Setter Property="Margin" Value="0" /> 
           <Setter Property="Template"> 
            <Setter.Value> 
             <ControlTemplate TargetType="ListViewItem"> 
              <ListViewItemPresenter 
               SelectedBackground="{StaticResource LightStandardColorBrush}" 
               SelectedPointerOverBackground="{StaticResource LightStandardColorBrush}" 
               PressedBackground="{StaticResource LightStandardColorBrush}" 
               SelectedPressedBackground="{StaticResource LightStandardColorBrush}"/> 

             </ControlTemplate> 
            </Setter.Value> 
           </Setter> 
          </Style> 
         </ListView.ItemContainerStyle> 

         <interactivity:Interaction.Behaviors> 
          <core:EventTriggerBehavior EventName="Tapped"> 
           <core:InvokeCommandAction Command="{Binding PostItemTapped}" CommandParameter="{Binding ElementName=PostListView, Path=SelectedItem}"/> 
          </core:EventTriggerBehavior> 
         </interactivity:Interaction.Behaviors> 
        </ListView> 

Answer 1

можно сделать двумя способами

1) Вы можете прослушать событие PointerEntered в listview

<ListView PointerEntered="PointerEntered" x:Name="PostListView" > 
.... 
</ListView> 

private void PointerEntered(object sender, PointerRoutedEventArgs e) 
     { 
      listScrollviewer = Scrolling(PostListView); 
     } 

     private ScrollViewer Scrolling(DependencyObject depObj) 
     { 
      ScrollViewer foundOne = GetScrollViewer(depObj); 
      if (foundOne != null) 
      { 
       // if (foundOne.VerticalOffset == 0) 
       // //refresh.Visibility = Visibility.Visible; 
       // else 
       //refresh.Visibility = Visibility.Collapsed; 
       foundOne.ViewChanging += foundOne_ViewChanging; 
      } 


      return foundOne; 
     } 

     public static ScrollViewer GetScrollViewer(DependencyObject depObj) 
     { 
      if (depObj is ScrollViewer) return depObj as ScrollViewer; 

      for (int i = 0; i < VisualTreeHelper.GetChildrenCount(depObj); i++) 
      { 
       var child = VisualTreeHelper.GetChild(depObj, i); 

       var result = GetScrollViewer(child); 
       if (result != null) return result; 
      } 
      return null; 
     } 

     private void foundOne_ViewChanging(object sender, ScrollViewerViewChangingEventArgs e) 
     { 
      //YOur logic to hide the button 
      if (e.NextView.VerticalOffset == 0) 
      { 
      } 
      else 
      { 
       //Hide the button 
      } 

     } 

2) Второй способ - отредактировать стиль списка. Там вы получите scrollviewer

<ListView Style="{StaticResource ListViewStyle1}"> 
... 
</ListView> 

<Style x:Key="ListViewStyle1" TargetType="ListView"> 
      <Setter Property="IsTabStop" Value="False"/> 
      <Setter Property="TabNavigation" Value="Once"/> 
      <Setter Property="IsSwipeEnabled" Value="True"/> 
      <Setter Property="HorizontalContentAlignment" Value="Stretch"/> 
      <Setter Property="VerticalContentAlignment" Value="Bottom"/> 
      <Setter Property="ScrollViewer.HorizontalScrollBarVisibility" Value="Disabled"/> 
      <Setter Property="ScrollViewer.VerticalScrollBarVisibility" Value="Auto"/> 
      <Setter Property="ScrollViewer.HorizontalScrollMode" Value="Disabled"/> 
      <Setter Property="ScrollViewer.VerticalScrollMode" Value="Auto"/> 
      <Setter Property="ScrollViewer.ZoomMode" Value="Disabled"/> 
      <Setter Property="ScrollViewer.IsDeferredScrollingEnabled" Value="False"/> 
      <Setter Property="ScrollViewer.BringIntoViewOnFocusChange" Value="True"/> 
      <Setter Property="ItemContainerTransitions"> 
       <Setter.Value> 
        <TransitionCollection> 
         <AddDeleteThemeTransition/> 
         <ReorderThemeTransition/> 
        </TransitionCollection> 
       </Setter.Value> 
      </Setter> 
      <Setter Property="ItemsPanel"> 
       <Setter.Value> 
        <ItemsPanelTemplate> 
         <ItemsStackPanel Orientation="Vertical"/> 
        </ItemsPanelTemplate> 
       </Setter.Value> 
      </Setter> 
      <Setter Property="Template"> 
       <Setter.Value> 
        <ControlTemplate TargetType="ListView"> 
         <Border BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Background="{TemplateBinding Background}"> 
          <ScrollViewer x:Name="ScrollViewer" AutomationProperties.AccessibilityView="Raw" BringIntoViewOnFocusChange="{TemplateBinding ScrollViewer.BringIntoViewOnFocusChange}" HorizontalScrollMode="{TemplateBinding ScrollViewer.HorizontalScrollMode}" HorizontalScrollBarVisibility="{TemplateBinding ScrollViewer.HorizontalScrollBarVisibility}" IsHorizontalRailEnabled="{TemplateBinding ScrollViewer.IsHorizontalRailEnabled}" IsHorizontalScrollChainingEnabled="{TemplateBinding ScrollViewer.IsHorizontalScrollChainingEnabled}" IsVerticalScrollChainingEnabled="{TemplateBinding ScrollViewer.IsVerticalScrollChainingEnabled}" IsVerticalRailEnabled="{TemplateBinding ScrollViewer.IsVerticalRailEnabled}" IsDeferredScrollingEnabled="{TemplateBinding ScrollViewer.IsDeferredScrollingEnabled}" TabNavigation="{TemplateBinding TabNavigation}" VerticalScrollBarVisibility="{TemplateBinding ScrollViewer.VerticalScrollBarVisibility}" VerticalScrollMode="{TemplateBinding ScrollViewer.VerticalScrollMode}" ZoomMode="{TemplateBinding ScrollViewer.ZoomMode}"> 
           <ItemsPresenter FooterTransitions="{TemplateBinding FooterTransitions}" FooterTemplate="{TemplateBinding FooterTemplate}" Footer="{TemplateBinding Footer}" HeaderTemplate="{TemplateBinding HeaderTemplate}" Header="{TemplateBinding Header}" HeaderTransitions="{TemplateBinding HeaderTransitions}" HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" Padding="{TemplateBinding Padding}" VerticalAlignment="{TemplateBinding VerticalContentAlignment}"/> 
          </ScrollViewer> 
         </Border> 
        </ControlTemplate> 
       </Setter.Value> 
      </Setter> 
     </Style>