WPF listbox UI虚拟化

ListBox  默认是UI虚拟化的。

1. 原生使用 

 <ListBox VirtualizingPanel.IsVirtualizing="True"
          VirtualizingPanel.VirtualizationMode="Recycling">
        </ListBox>

 为ListBox 设置一个ItemTemplate

 <DataTemplate x:Key="ListBoxDataTemplate">
            <Grid Loaded="Grid_Loaded">
                <Label Content="{Binding Name}"></Label>
            </Grid>
        </DataTemplate>

在 Grid_Loaded 事件中可以看到 实例化的次数

        int index = 0;
        private void Grid_Loaded(object sender, RoutedEventArgs e)
        {
            Console.WriteLine(index);
            index++;
        }

2. 当修改 ListBox   的Template属性时 ，UI虚拟化就失效了

<Setter Property="Template">
                <Setter.Value>
                    <ControlTemplate TargetType="{x:Type ListBox}">
                        <ScrollViewer x:Name="ScrollViewer"  CanContentScroll="false">
                            <ItemsPresenter  />
                        </ScrollViewer>
                    </ControlTemplate>
                </Setter.Value>
            </Setter>

这是标配写法ScrollViewer 中包裹 <ItemsPresenter />

这时ScrollViewer 控件的 CanContentScroll="false"(物理滚动) 要改为 CanContentScroll="true"(逻辑滚动)

ListBox 默认是逻辑滚动，（一项一项滚动）。改变模板时，需要重新设置

附件属性 ScrollViewer.CanContentScroll="True" 这个时候Ui虚拟化重新出现

3.修改Listbox 的ItemsPanel 模板添加一下代码也是可以ui虚拟化（除非你修改了ItemsPanel 模板，因为默认就是虚拟化的。）

 <Setter Property="ItemsPanel">
                <Setter.Value>
                    <ItemsPanelTemplate >
                        <VirtualizingStackPanel   Orientation="Vertical"/>
                    </ItemsPanelTemplate>
                </Setter.Value>
            </Setter>

全部代码

<Window x:Class="VirtualizingStackPanelDemo.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="350" Width="525">
    <Window.Resources>
        <DataTemplate x:Key="ListBoxDataTemplate">
            <Grid Loaded="Grid_Loaded">
                <Label Content="{Binding Name}"></Label>
            </Grid>
        </DataTemplate>
        <Style x:Key="ListBoxStyle" TargetType="{x:Type ListBox}">
            <Setter Property="BorderThickness" Value="0"></Setter>
            <Setter Property="Margin" Value="0 0 5 0"></Setter>
            <Setter Property="MinWidth" Value="150"></Setter>
            <Setter Property="MaxHeight" Value="350"></Setter>
            <Setter Property="Height" Value="350"></Setter>
            <Setter Property="SnapsToDevicePixels" Value="True" />
            <Setter Property="ScrollViewer.CanContentScroll" Value="True"></Setter>
            <Setter Property="Template">
                <Setter.Value>
                    <ControlTemplate TargetType="{x:Type ListBox}">
                        <ScrollViewer x:Name="ScrollViewer"  CanContentScroll="True">
                            <ItemsPresenter  />
                        </ScrollViewer>
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
            <!--<Setter Property="ItemsPanel">
                <Setter.Value>
                    <ItemsPanelTemplate >
                        <VirtualizingStackPanel   Orientation="Vertical"/>
                    </ItemsPanelTemplate>
                </Setter.Value>
            </Setter>-->
        </Style>
    </Window.Resources>
    <Grid>
        <ListBox Style="{StaticResource ListBoxStyle}" ItemTemplate="{StaticResource  ListBoxDataTemplate}" x:Name="listbox"></ListBox>
    </Grid>
</Window>

总结 ：

1.Listbox 默认虚拟化

2.修改ListBox Template时 ，重新设置ListBox 附加属性ScrollViewer.CanContentScroll 为"True"，以及

<ScrollViewer CanContentScroll="True">

<ItemsPresenter />

</ScrollViewer>

来自为知笔记(Wiz)