Perché il riciclaggio non funziona?

Question

Abbiamo un'applicazione desktop, in cui abbiamo una ListView, il ListView.ItemTemplate è un KPageScrollViewer estendentesi ScrollViewer

Sebbene abbiamo impostato VirtualizingStackPanel.IsVirtualizing="True" e VirtualizingStackPanel.VirtualizationMode="Recycling"

Abbiamo notato che il costruttore di KPageScrollViewer (che è all'interno della ItemTemplate) viene sempre eseguito durante la visualizzazione degli elementi all'interno di ListView.

Quello che ci aspettavamo è che verrà creato da 4 a 5 volte, quindi, le stesse istanze verranno utilizzate per visualizzare i dati perché stiamo usando la modalità di riciclaggio, ma ciò non accadrà, quindi finiremo con più e più istanze di KPageScrollViewer create ..

È perché abbiamo personalizzato ListView.ItemsPanel?

<ListView.ItemsPanel> 
    <ItemsPanelTemplate > 
     <p:KVirtualizingStackPanel IsItemsHost="True" 

Qualche idea per favore? Mi chiedo quali motivi potrebbero portare a perdere funzionalità di riciclaggio?

<ListView x:Class="KETAB.KStudio.Stage.PagesView" 
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
    xmlns:p="clr-namespace:KETAB.KStudio.Stage" 
    Name="PagesList" ScrollViewer.HorizontalScrollBarVisibility="Hidden" ScrollViewer.VerticalScrollBarVisibility="Hidden" 
    Loaded="instScroll_Loaded" 
    AllowDrop="True" 
    MouseMove="PagesList_MouseMove" 
    ScrollViewer.PanningMode="None" 
    VirtualizingStackPanel.IsVirtualizing="True" 
    VirtualizingStackPanel.CleanUpVirtualizedItem="PagesList_CleanUpVirtualizedItem" 
    VirtualizingStackPanel.VirtualizationMode="Recycling" 
    > 

    <ListView.Resources> 
     <ResourceDictionary> 
      <ResourceDictionary.MergedDictionaries> 
       <ResourceDictionary Source="Resources/StageResources.xaml"/> 
       <ResourceDictionary Source="/KETAB.KStudio.UserControls;component/ScrollViewerStyle.xaml" /> 
      </ResourceDictionary.MergedDictionaries> 
      <SolidColorBrush x:Key="{x:Static SystemColors.HighlightBrushKey}" Opacity="0.4" Color="Transparent" /> 
      <SolidColorBrush x:Key="{x:Static SystemColors.ControlBrushKey}" Opacity="0.4" Color="Transparent" /> 
      <!--<p:PageWidthConverter x:Key="PageWidthConverter" />--> 
      <p:PageWidthConverter x:Key="pageWidthConverter" /> 
      <p:PageHeightConverter x:Key="pageHeightConverter" /> 
      <Style TargetType="{x:Type ListViewItem}"> 
       <Setter Property="Template"> 
        <Setter.Value> 
         <ControlTemplate TargetType="{x:Type ListViewItem}"> 
          <ContentPresenter HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}" VerticalAlignment="{TemplateBinding VerticalContentAlignment}"/> 
         </ControlTemplate> 
        </Setter.Value> 
       </Setter> 
       <Setter Property="FocusVisualStyle" 
      Value="{x:Null}"/> 
      </Style> 
     </ResourceDictionary> 
    </ListView.Resources> 

    <ListView.ItemTemplate> 
     <DataTemplate x:Name="PagesViewDataTemplate"> 
      <DataTemplate.Resources> 
       <Style x:Key="PageHostStyle" TargetType="{x:Type p:KPage}"> 
       </Style> 
      </DataTemplate.Resources> 
      <p:KPageScrollViewer Name="ScrollContainer" 
           Padding="{Binding ElementName=PagesList, Path=PageScrollViewerPadding}" 
           Height="{Binding ElementName=PagesList, Path=ScaleY, Converter={StaticResource pageHeightConverter}}" 
           Width="{Binding ElementName=PagesList, Path=ScaleX, Converter={StaticResource pageWidthConverter}}" 
           MaxHeight="{Binding ElementName=PagesList, Path=Height}" 
           MaxWidth="{Binding ElementName=PagesList, Path=Width}"  
           ScrollViewer.HorizontalScrollBarVisibility="{Binding ElementName=PagesList, Path=PageScrollVisibilityHori}" 
           ScrollViewer.VerticalScrollBarVisibility="{Binding ElementName=PagesList, Path=PageScrollVisibilityVert}"         > 
       <Grid x:Name="MarginStack" > 
        <p:KPage x:Name="KPage" SizeChanged="KPage_SizeChanged" > 

        </p:KPage> 
       </Grid> 
      </p:KPageScrollViewer> 
     </DataTemplate> 
    </ListView.ItemTemplate> 

    <ListView.ItemsPanel> 
     <ItemsPanelTemplate > 
      <p:KVirtualizingStackPanel IsItemsHost="True" 
           x:Name="WrapPanel1" 
           Orientation="{Binding ElementName=PagesList, Path=MyOrientation}" 
           VerticalAlignment="Center" 
           HorizontalAlignment="Center" 
           ClipToBounds="{Binding ElementName=PagesList, Path=PanelClipToBounds}"   
           Height="{Binding ElementName=PagesList, Path=ScaleY, Converter={StaticResource pageHeightConverter}}" 
           Width="{Binding ElementName=PagesList, Path=ScaleX, Converter={StaticResource pageWidthConverter}}" 
           MaxHeight="{Binding ElementName=PagesList, Path=Height}" 
           MaxWidth="{Binding ElementName=PagesList, Path=Width}"  
           > 
      </p:KVirtualizingStackPanel> 
     </ItemsPanelTemplate> 
    </ListView.ItemsPanel> 

</ListView> 

EDIT

Qui è dove viene utilizzato il ListView: (p: PagesView)

<Window x:Class="KETAB.KStudio.UI.WindowMain" 
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"  
    xmlns:kStudioControls="clr-namespace:KETAB.KStudio.UI" 
    xmlns:toolBoxUIPanel="clr-namespace:KETAB.KStudio.UI" 
    xmlns:Controls="clr-namespace:KETAB.KStudio.UserControls;assembly=KETAB.KStudio.UserControls" 
    xmlns:p="clr-namespace:KETAB.KStudio.Stage;assembly=KETAB.KStudio.Stage" 
    xmlns:tb="http://www.hardcodet.net/taskbar" 
    SizeChanged="Window_SizeChanged"  
    WindowState="Maximized" 
    WindowStyle="None" 
    Background="Transparent" 
    ResizeMode="CanResizeWithGrip" 
    PreviewKeyUp="WindowMain_PreviewKeyUp" 
    Closed="WindowMain_Closed" 
    Stylus.IsPressAndHoldEnabled="False" 
    Stylus.IsTapFeedbackEnabled="False" 
    Stylus.IsTouchFeedbackEnabled="False" 
    Stylus.IsFlicksEnabled="False" 
    AllowsTransparency="True"> 

    <Grid FlowDirection="LeftToRight" Name="MainUIContainer"> 
     <Grid.RowDefinitions> 
      <RowDefinition Height="auto" MinHeight="0" /> 
      <RowDefinition /> 
     </Grid.RowDefinitions> 

     <tb:TaskbarIcon 
        x:Name="MyNotifyIcon" 
        IconSource="/KETABStudio;component/KStudioControls/KStudioIcons/Notify.ico" 
        ToolTipText="KETAB Studio" Visibility="Collapsed"/> 

     <Border Name="borderContainer" ClipToBounds="True" Margin="0,0,0,0" Grid.Row="1" Grid.Column="0" BorderThickness="2, 0, 2, 2" 
       BorderBrush="{StaticResource MainWindowBorderColor}" Background="White"> 
      <Grid Background="Transparent" ClipToBounds="True" Name="MainUISplit" SizeChanged="MainUISplit_SizeChanged"> 
       <!--main backgound depends on this grid--> 
       <Grid.RowDefinitions> 
        <RowDefinition /> 
       </Grid.RowDefinitions> 
       <Grid.ColumnDefinitions> 
        <ColumnDefinition Width="*" /> 
        <ColumnDefinition Width="auto" /> 
       </Grid.ColumnDefinitions> 

       <Grid Background="{StaticResource background}" Margin="0" ClipToBounds="True" Name="applicationBackground"> 
        <Rectangle Name="OpacityRectangle" Visibility="Hidden" Margin="0,0,-60,0" Fill="Black" ></Rectangle>      
       </Grid> 

       <!--Page Area--> 
       <Grid Grid.Column="0" Grid.Row="0" Margin="0" Name="PageArea" AllowDrop="True"> 
        <p:PagesView Name="PageList" /> 
        <Controls:PageLoadingControl x:Name="pageLoadingControl" Visibility="Collapsed"/> 
        <Controls:HelpMode x:Name="HelpModeInstance" Visibility="Collapsed"/> 
       </Grid> 
      </Grid> 
     </Border> 
    </Grid> 
</Window> 

Answer 1

ho letto il seguente che può essere di aiuto ... ha a che fare con il modo in cui stai usando il ItemsPanel: Virtualizing an ItemsControl? - Mi rendo conto che non è esattamente lo stesso argomento, ma ha una buona spiegazione su un problema molto simile.

Speriamo che possa essere d'aiuto.