UWP的GridView ItemTemplateSelector在SemanticZoom不适用

Question

我有一个GridView如在SemanticZoom控制我的缩小视图。该GridView使用自定义的DataTemplateSelector作为ItemTemplateSelector。该DataTemplateSelector返回与不同的前景色一个DataTemplate，根据集团是否有其中的任何项目。

然而，即使DataTemplateSelector似乎工作，并返回正确的模板，只有一个模板使用过由GridView和文本都是相同的颜色。

这里是GroupedListView的XAML：

<UserControl 
    x:Class="GroupList.GroupList.GroupedListView" 
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
    xmlns:local="using:GroupList.GroupList" 
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
    xmlns:data="using:GroupList.Model" 
    xmlns:wuxdata="using:Windows.UI.Xaml.Data" 
    mc:Ignorable="d"> 

    <UserControl.Resources> 
     <!-- Use a collection view source for content that presents itself as a list of items that can be grouped or sorted. Otherwise, you can use x:Bind 
     directly on the ListView's item source to for further optimization. Please see the AppUIBasics sample for an example of how to do this. --> 
     <CollectionViewSource x:Name="ContactsCVS" IsSourceGrouped="True" /> 

     <Style TargetType="TextBlock" x:Key="TileHeaderTextStyle" BasedOn="{StaticResource ProximaNovaSemiBold}"> 
      <Setter Property="FontSize" Value="54" /> 
      <Setter Property="Foreground" Value="White" /> 
      <Setter Property="FontWeight" Value="ExtraBold"/> 
      <Setter Property="FontStretch" Value="Expanded" /> 
     </Style> 

     <Style TargetType="TextBlock" x:Key="TileHeaderTextStyleGray" BasedOn="{StaticResource TileHeaderTextStyle}"> 
      <Setter Property="Foreground" Value="Khaki" /> 
     </Style> 

     <!-- When using x:Bind, you need to set x:DataType --> 
     <DataTemplate x:Name="ContactListViewTemplate" x:DataType="data:Contact"> 
      <Grid> 
       <Grid.RowDefinitions> 
        <RowDefinition Height="*"/> 
        <RowDefinition Height="*"/> 
       </Grid.RowDefinitions> 
       <Grid.ColumnDefinitions> 
        <ColumnDefinition Width="Auto"/> 
        <ColumnDefinition Width="*"/> 
       </Grid.ColumnDefinitions> 
       <Ellipse x:Name="Ellipse" 
         Grid.RowSpan="2" 
         Width ="32" 
         Height="32" 
         Margin="6" 
         VerticalAlignment="Center" 
         HorizontalAlignment="Center" 
         Fill="LightGray"/> 
       <TextBlock Grid.Column="1" 
          Text="{x:Bind Name}" 
          x:Phase="1" 
          Style="{ThemeResource BaseTextBlockStyle}" 
          Margin="12,6,0,0"/> 
       <TextBlock Grid.Column="1" 
          Grid.Row="1" 
          Text="{x:Bind Position}" 
          x:Phase="2" 
          Style="{ThemeResource BodyTextBlockStyle}" 
          Margin="12,0,0,6"/> 
      </Grid> 
     </DataTemplate> 
     <DataTemplate x:Key="GrayZoomedOutTemplate" x:DataType="wuxdata:ICollectionViewGroup"> 
      <TextBlock Text="{x:Bind Group.(data:GroupInfoList.Key)}" Margin="0,0,0,5" Style="{StaticResource TileHeaderTextStyleGray}" /> 
     </DataTemplate> 
     <DataTemplate x:Key="ZoomedOutTemplate" x:DataType="wuxdata:ICollectionViewGroup"> 
      <TextBlock Text="{x:Bind Group.(data:GroupInfoList.Key)}" Margin="0,0,0,5" Style="{StaticResource TileHeaderTextStyle}" /> 
     </DataTemplate> 
     <local:GroupEmptyOrFullSelector x:Key="GroupEmptyOrFullSelector" Empty="{StaticResource GrayZoomedOutTemplate}" Full="{StaticResource ZoomedOutTemplate}" /> 
    </UserControl.Resources> 
    <!--#region Navigation Panel --> 
    <Grid> 
     <Grid.RowDefinitions> 
      <RowDefinition Height="Auto"/> 
      <RowDefinition Height="*"/> 
     </Grid.RowDefinitions> 
     <StackPanel Orientation="Vertical"> 
      <TextBlock Margin="15,0,0,0" Text="Paula's SemanticZoom Sandbox" Grid.Row="0" 
          VerticalAlignment="Center" 
          Style="{ThemeResource TitleTextBlockStyle}" /> 
      <Button x:Name="ZoomInOutBtn" Content="ABC↕" Click="ZoomInOutBtn_Click" Width="60" HorizontalAlignment="Center" BorderThickness="0" /> 
     </StackPanel> 
     <!--#endregion--> 
     <SemanticZoom x:Name="ZoomControl" Grid.Row="1"> 
      <SemanticZoom.ZoomedInView> 
       <GridView ItemsSource="{x:Bind ContactsCVS.View}" 
          ItemTemplate="{StaticResource ContactListViewTemplate}" 
          SelectionMode="Single" 
          ShowsScrollingPlaceholders="True"> 

        <GridView.GroupStyle> 
         <GroupStyle HidesIfEmpty="True"> 
          <GroupStyle.HeaderTemplate> 
           <DataTemplate x:DataType="data:GroupInfoList"> 
            <TextBlock Text="{x:Bind Key}" 
               Style="{ThemeResource TitleTextBlockStyle}" /> 
           </DataTemplate> 
          </GroupStyle.HeaderTemplate> 
         </GroupStyle> 
        </GridView.GroupStyle> 
       </GridView> 
      </SemanticZoom.ZoomedInView> 
      <SemanticZoom.ZoomedOutView> 
       <GridView ItemTemplateSelector="{StaticResource GroupEmptyOrFullSelector}" ScrollViewer.VerticalScrollBarVisibility="Disabled" Margin="0, 200" Width="475" ItemsSource="{x:Bind ContactsCVS.View.CollectionGroups}" SelectionMode="None" > 
       </GridView> 
      </SemanticZoom.ZoomedOutView> 
     </SemanticZoom> 
    </Grid> 
</UserControl> 

这里是DataTemplateSelector：

using System; 
using System.Collections.Generic; 
using System.Linq; 
using System.Text; 
using System.Threading.Tasks; 
using Windows.UI.Xaml; 
using Windows.UI.Xaml.Controls; 
using Windows.UI.Xaml.Controls.Primitives; 
using Windows.Foundation.Collections; 
using GroupList.Model; 

namespace GroupList.GroupList 
{ 
    /// <summary> 
    /// This determines whether or not the Group passed during binding is empty or not and allows selection 
    /// of the proper DataTemplate based on this value. 
    /// </summary> 
    class GroupEmptyOrFullSelector : DataTemplateSelector 
    { 
     private DataTemplate _full; 
     private DataTemplate _empty; 
     public DataTemplate Full 
     { 
      set { _full = value; } 
      get { return _full; } 
     } 
     public DataTemplate Empty 
     { 
      set { _empty = value; } 
      get { return _empty; } 
     } 


     protected override DataTemplate SelectTemplateCore(object item, DependencyObject container) 
     { 

      var itemType = item.GetType(); 
      var isGroup = itemType.Name == "GroupInfoList"; 
      bool isEmpty = false; 
      GroupInfoList groupItem; 

      if (isGroup) 
      { 
       groupItem = item as GroupInfoList; 
       isEmpty = groupItem.Count == 0; 
      } 

      // Disable empty items 
      var selectorItem = container as SelectorItem; 
      if (selectorItem != null) 
      { 
       selectorItem.IsEnabled = !isEmpty; 
      } 

      if (isEmpty) 
      { 
       return Empty; 
      } 
      else 
      { 
       return Full; 
      } 
     } 
    } 
} 

Answer 1

所以，在这里就是问题所在：

在DataTemplateSelector上市，即使一个通过的“对象项目”不是一个组，它落入了模板选择逻辑。有时，传递给你的函数的“对象”不是一个Group对象，而是一个泛型的DependencyObject。在这种情况下，你的模板选择逻辑需要返回默认模板，返回的仅在“目标项目”是一组对象的特定模板之一。因此，新功能如下所示：

protected override DataTemplate SelectTemplateCore(object item, DependencyObject container) 
    { 

     var itemType = item.GetType(); 
     var isGroup = itemType.Name == "GroupInfoList"; 
     bool isEmpty = false; 
     GroupInfoList groupItem; 

     if (isGroup) 
     { 
      groupItem = item as GroupInfoList; 
      isEmpty = groupItem.Count == 0; 

      // Disable empty items 
      var selectorItem = container as SelectorItem; 
      if (selectorItem != null) 
      { 
       selectorItem.IsEnabled = !isEmpty; 
      } 

      if (isEmpty) 
      { 
       return Empty; 
      } 
      else 
      { 
       return Full; 
      } 

     } 

     return Full; 

    }