如何在 ItemsControls 中使用 AlternationIndex? [英] How to use AlternationIndex in ItemsControls?

问题描述

我看过一些文章，展示了如何将 AlternationIndex 与 ListBoxes 或 ListViews 一起使用，但我花了几个小时尝试在基础 ItemsControl 类上获得交替的背景颜色，但似乎没有任何效果.我看到的所有 ListBox 示例都使用 ListBoxItem 作为基于 AlternationIndex 设置背景的样式的目标类型 - 就像来自 MSDN:

I have seen some articles that show how to use AlternationIndex with ListBoxes or ListViews, but I had spent a few hours trying to get alternating background colors on the base ItemsControl class and nothing seems to work. All ListBox samples I saw use ListBoxItem as the target type for the style that sets the background based onAlternationIndex - like this one from MSDN:

<Grid>
    <Grid.Resources>
        <Style x:Key="alternatingWithTriggers" TargetType="{x:Type ListBoxItem}">
            <Setter Property="Background" Value="Blue"/>
            <Setter Property="Foreground" Value="White"/>
            <Style.Triggers>
                <Trigger Property="ListBox.AlternationIndex" Value="1">
                    <Setter Property="Background" Value="CornflowerBlue"/>
                    <Setter Property="Foreground" Value="Black"/>
                </Trigger>
                <Trigger Property="ListBox.AlternationIndex" Value="2">
                    <Setter Property="Background" Value="LightBlue"/>
                    <Setter Property="Foreground" Value="Navy"/>
                </Trigger>
            </Style.Triggers>
        </Style>

    </Grid.Resources>
    <ListBox AlternationCount="3" ItemsSource="{StaticResource data}" 
             ItemContainerStyle="{StaticResource alternatingWithTriggers}">
    </ListBox>
</Grid>

我想使用 ItemsControl 因为我不想要选择功能，我认为重新设计 ListBox 以隐藏它可能不是最好的选择.

I want to use the ItemsControl because I do not want the selection functionality and I think restyling a ListBox to hide it might not be the best choice.

这是我正在尝试的事情之一:

This is one of the things I was trying:

<DataTemplate DataType="{x:Type vm:ObservableCollectionItem}">
    <Grid>
        <!-- some content here -->
    </Grid>
</DataTemplate>

<!-- ... -->

<ItemsControl
    ItemsSource="{Binding ObservableCollectionItems}"
    AlternationCount="2"
>
    <ItemsControl.ItemContainerStyle>
        <Style>
            <Style.Triggers>
                <Trigger Property="ItemsControl.AlternationIndex" Value="0">
                    <Setter Property="Grid.Background" Value="Red"></Setter>
                </Trigger>
                <Trigger Property="ItemsControl.AlternationIndex" Value="1">
                    <Setter Property="Grid.Background" Value="Blue"></Setter>
                </Trigger>
            </Style.Triggers>
        </Style>
    </ItemsControl.ItemContainerStyle>
</ItemsControl>

我看到的问题是可视化树有一个 ContentPresenter 列表，其中 ItemsControl.AlternationIndex 在 0 和 1 之间交替，但 Grid<每个 ContentPresenter 中的/code> 将 ItemsControl.AlternationIndex 设置为 0.

The problem I saw was that the visual tree has a list of ContentPresenters that have ItemsControl.AlternationIndex alternate between 0 and 1, but the Grid in each ContentPresenter has ItemsControl.AlternationIndex set to 0.

我可能遗漏了一些明显的东西......

There is probably something obvious I am missing...

推荐答案

ItemContainerStyle 应用于由 ItemsControl: ContentPresenter 生成的元素.ContentPresenter 将依次包含您放入 ItemTemplate 的任何内容.在 ListBox 的情况下，ItemContainerStyle 应用于生成的 ListBoxItem.

The ItemContainerStyle is applied to the elements generated by the ItemsControl: ContentPresenter. The ContentPresenter will in turn contain whatever you put in your ItemTemplate. In the case of a ListBox, the ItemContainerStyle is applied to the generated ListBoxItem.

根据您发布的内容，AlternationCount 仅适用于这些生成的项目.您不能使用 ItemContainerStyle 来设置 Grid 的背景，因为该样式不知道 Grid.

The AlternationCount is, based on what you posted, only available on these generated items. You cannot use the ItemContainerStyle to set the Grid's background, because the Grid is unknown to that Style.

以下是理想的，但不幸的是 ContentPresenter 没有背景属性.但是，它适用于 ListBox(带有 ListBoxItems).

The following would be ideal, but unfortunately ContentPresenter has no background property. It would work for a ListBox (with ListBoxItems) however.

<ItemsControl
    ItemsSource="{Binding ObservableCollectionItems}"
    AlternationCount="2">
    <ItemsControl.ItemContainerStyle>
        <Style TargetType="ContentPresenter">
            <Style.Triggers>
                <Trigger Property="ItemsControl.AlternationIndex" Value="0">
                    <Setter Property="Background" Value="Red"></Setter>
                </Trigger>
                <Trigger Property="ItemsControl.AlternationIndex" Value="1">
                    <Setter Property="Background" Value="Blue"></Setter>
                </Trigger>
            </Style.Triggers>
        </Style>
    </ItemsControl.ItemContainerStyle>
</ItemsControl>

因此，您最终为网格编写了一个样式，该样式绑定到您的父 ContentPresenter 的 AlternationIndex.

So you end up writing a style for the grid which binds to the AlternationIndex of your parent ContentPresenter.

<DataTemplate DataType="{x:Type vm:ObservableCollectionItem}">
    <Grid>
        <Grid.Style>
            <Style TargetType="Grid">
                <Style.Triggers>
                    <DataTrigger Binding="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type ContentPresenter}}, Path=(ItemsControl.AlternationIndex)}" Value="0">
                        <Setter Property="Background" Value="Red"/>
                    </DataTrigger>
                    <DataTrigger Binding="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type ContentPresenter}}, Path=(ItemsControl.AlternationIndex)}" Value="1">
                        <Setter Property="Background" Value="Blue"/>
                    </DataTrigger>
                </Style.Triggers>
            </Style>
        </Grid.Style>
    </Grid>
</DataTemplate>

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