用户控件的数据模板选择器

Question

我有一个列表框，我想在 UWP 应用程序中加载不同类型的用户控件。

我需要 UserControls 的原因是因为列表中显示的每个项目都需要代码隐藏，所以简单的 DataTemplate 无法解决问题。

我在行

上遇到错误

<converters:HomeWidgetControlPicker>

在列表框中。

The specified value cannot be assigned. The following type was expected: "DependencyObject".

如何加载 UserControl？我在一个旧的 UWP 应用程序中使用了这个方法并且它在那里工作，但在我的新项目中它没有。

我不能使用 x:DataType，因为所有项目都是相同的 class (HomeWidget)，但是根据 HomeWidget 的类型属性选择了正确的 UserControl。

我做了一个DataTemplateSelector：

public class HomeWidgetControlPicker : DataTemplateSelector
{
    public DataTemplate Artist { get; set; }
    public DataTemplate Release { get; set; }

    protected override DataTemplate SelectTemplateCore(object item, DependencyObject container)
    {
        if (item != null)
        {
            var result = (HomeWidget)item;

            if (result.Type == "artist")
            {
                return Artist;
            }

            if (result.Type == "release")
            {
                return Release;
            }
        }
        return null;
    }
}

我有一个列表框，目前只使用类型 (HomeWidgetControlPicker.Artist)，但以后会更多。

        <ListBox x:Name="wrapGrid" ItemContainerStyle="{StaticResource WrapPanelBorderedItem}" ItemsSource="{x:Bind WidgetList}" Background="{x:Null}" ScrollViewer.VerticalScrollBarVisibility="Disabled" VerticalAlignment="Top" HorizontalAlignment="Center" >

            <ListBox.ItemsPanel>
                <ItemsPanelTemplate>
                    <userControls:WrapPanel/>
                </ItemsPanelTemplate>
            </ListBox.ItemsPanel>
            <ListBox.ItemTemplate>
                <DataTemplate>
                    <converters:HomeWidgetControlPicker>
                        <converters:HomeWidgetControlPicker.Artist>
                            <DataTemplate>
                                <homeItems:HomeArtist></homeItems:HomeArtist>
                            </DataTemplate>
                        </converters:HomeWidgetControlPicker.Artist>
                    </converters:HomeWidgetControlPicker>
                </DataTemplate>
            </ListBox.ItemTemplate>
        </ListBox>

Answer 1

你使用DataTemplateSelector的方式应该是错误的。在您的代码片段中，DataTemplateSelector 被放置为 DataTemplateSelector class 的 DataTemplate, but actually, you can use a DataTemplateSelector and set properties such as ItemTemplateSelector to assign it to a data view. See remarks section 的根元素以获取更多详细信息。

The base DataTemplateSelector class is not used as an object element in XAML. However, it is a common scenario to derive a custom DataTemplateSelector, map a xmlns prefix for the custom class and its namespace/assembly, and then refer to an instance of the custom class as defined in a Resources block in XAML. This makes it possible to refer to the custom template selector class by x:Key, and use that reference to set the value of properties such as ItemTemplateSelector in XAML templates and visual states.

例如：

<Page.Resources>
    <DataTemplate x:Key="Artist" x:DataType="local:HomeWidget">
        <Grid>           
            <local:UserControl1></local:UserControl1>
             ...               
        </Grid>
    </DataTemplate>
    <DataTemplate x:Key="Release" x:DataType="local:HomeWidget">
        <Grid>        
            <local:UserControl2></local:UserControl2> 
          ...             
        </Grid>
    </DataTemplate>
    <local:HomeWidgetControlPicker x:Key="HomeWidgetControlPicker" Artist="{StaticResource Artist}" Release="{StaticResource Release}">
    </local:HomeWidgetControlPicker>
</Page.Resources>

<Grid Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
    <ListBox x:Name="wrapGrid" ItemTemplateSelector="{StaticResource HomeWidgetControlPicker}"  ItemsSource="{x:Bind WidgetList}"  
     ...
    </ListBox>
</Grid>

用户控件的数据模板选择器

DataTemplateSelector for UserControl

user-controls

listbox

datatemplate

datatemplateselector

uwp