ListBox数据虚拟化未生效 [英] ListBox data virtualization is not taking effect

问题描述

我从xml中获得了1000个项目，并将它们加载到List对象中. List与水平方向的ListBox数据绑定，因此用户可以从左到右或从右到左翻转项目.由于项目数量巨大，我的应用程序退出可能是由于过多的内存使用.如果我将项目减少到50个，那就行了.

I had 1000 items from xml and loaded them in a List object. List is databound to ListBox which is horizontally oriented so user can flip through items left to right or right to left. Since number of items are huge my app was quitting probably due to excessive memory usage. If I reduced the items to 50 it worked.

我找到了这篇文章 http://shawnoster.com/blog/post/Improving-ListBox-Performance-in-Silverlight-for-Windows-Phone-7-Data-Virtualization.aspx

然后是关于数据虚拟化的文章

and then this article on data virtualization

http://blogs.msdn.com/b/ptorr/archive/2010/08/16/virtualizing-data-in-windows-phone-7-silverlight-applications.aspx

在实现了实现IList的虚拟化类之后，我发现没有区别.尽管我希望UI被已经在Listbox中虚拟化，但this [](下面)仍被调用1000次，尽管我希望它仅被调用30-40次.为什么虚拟化无法发挥作用?

After implementing a virtualized class implementing IList I see no difference. The this[] (below) is being called 1000 times still though I expected to it be called only 30-40 times since I understand UI is already virtualized in Listbox. Why is virtualization not kicking in?

object IList.this[int index]
{
    get
    {
        if (index >= cachedItems.Count)
        {
            //replenish cache code here
        }

        return cachedItems[index];
    }
    set
    {
        throw new NotImplementedException();
    }
}

这是与问题相关的XAML部分.希望这能提供完整的代码说明.不知道Width=Auto是否与它有任何关系，但是我无法更改它，否则我的刷卡操作会停止.

Here is the XAML portion relevant to the problem. Hope this gives the full picture of the code. Not sure if Width=Auto has anything to do with it but I can't change it otherwise my swiping stops.

<ScrollViewer HorizontalScrollBarVisibility="Auto" Margin="0,0,0,0" Width="auto" x:Name="WordsScrollview" Opacity="1"  Grid.Row="1" RenderTransformOrigin="0.5,0.5">

    <ListBox x:Name="horizontalListBox" Width="auto" Height="Auto" >

        <ListBox.ItemsPanel>
            <ItemsPanelTemplate>
                <StackPanel Orientation="Horizontal">
                </StackPanel>
            </ItemsPanelTemplate>
        </ListBox.ItemsPanel>

        <ListBox.ItemTemplate>
            <DataTemplate>
                <StackPanel>
                    <TextBlock Width="430" Text="{Binding Word}"  TextWrapping="Wrap" Style="{StaticResource PhoneTextExtraLargeStyle}" TextAlignment="Center" />
                    <Image Height="290" HorizontalAlignment="Center" Name="image1" Stretch="Fill"  Width="430" Source="{Binding ImageFile}" Margin="10,50,10,0" />
                </StackPanel>
            </DataTemplate>
        </ListBox.ItemTemplate>

        <ListBox.Background>
            <SolidColorBrush />
        </ListBox.Background>

    </ListBox>

</ScrollViewer>

推荐答案

这是导致UI虚拟化最终启动的XAML.

Here is the XAML that is causing UI Virtualization to finally kick in.

        <ListBox x:Name="horizontalListBox"   Height="Auto" ScrollViewer.HorizontalScrollBarVisibility="Auto" >

                <ListBox.ItemsPanel>
                    <ItemsPanelTemplate>
                        <VirtualizingStackPanel Orientation="Horizontal">

                        </VirtualizingStackPanel>
                    </ItemsPanelTemplate>
                </ListBox.ItemsPanel>
                <ListBox.ItemTemplate>
                    <DataTemplate>

                            <StackPanel>
                                <TextBlock Width="430" Text="{Binding Word}"  TextWrapping="Wrap" Style="{StaticResource PhoneTextExtraLargeStyle}" TextAlignment="Center" />

                                <Image Height="290" HorizontalAlignment="Center" Name="image1" Stretch="Fill"  Width="430" Source="{Binding ImageFile}" Margin="10,50,10,0" />
                               </StackPanel>

                    </DataTemplate>
                </ListBox.ItemTemplate>
                <ListBox.Background>
                    <SolidColorBrush />
                </ListBox.Background>
            </ListBox>

这篇关于ListBox数据虚拟化未生效的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！