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)