UWP 从模板化 TabViewItem 获取 Children

Question

我使用以下方法获得了 TabViewItem：

        var tab = PlaylistTabView.ContainerFromIndex(PlaylistTabView.SelectedIndex);

但是，我似乎没有访问正确的 children。

这是 TabView.ItemTemplate 的 xaml，其中 PlaylistControl 是我的自定义控件，基本上只是一个 ListView:

        <controls:TabView.ItemTemplate>
            <DataTemplate x:DataType="data:Playlist">
                <local:PlaylistControl
                    AllowReorder="False"
                    AlternatingRowColor="True"
                    ItemsSource="{x:Bind Songs, Mode=OneWay}">
                    <local:PlaylistControl.Header>
                        <controls:ScrollHeader Mode="Sticky">
                            <Grid
                                x:Name="PlaylistInfoGrid"
                                Padding="30"
                                Background="#222222"
                                RequestedTheme="Dark">
                                <Grid.RowDefinitions>
                                    <RowDefinition Height="Auto" />
                                    <RowDefinition Height="Auto" />
                                    <RowDefinition Height="Auto" />
                                </Grid.RowDefinitions>
                                <Grid.ColumnDefinitions>
                                    <ColumnDefinition Width="Auto" />
                                    <ColumnDefinition Width="*" />
                                </Grid.ColumnDefinitions>
                                <Image
                                    x:Name="PlaylistCover"
                                    Grid.RowSpan="4"
                                    Width="180"
                                    Height="180"
                                    Margin="0,0,20,0"
                                    Source="Assets/monotone_bg_wide.png" />
                                <TextBlock
                                    Grid.Column="1"
                                    FontSize="36"
                                    Style="{StaticResource HeaderTextBlockStyle}"
                                    Text="{x:Bind Name, Mode=OneWay}" />
                                <TextBlock
                                    Grid.Row="1"
                                    Grid.Column="1"
                                    Margin="0,5"
                                    Text="{x:Bind Songs, Converter={StaticResource SongCountConverter}, Mode=OneWay}" />
                                <CommandBar
                                    Grid.Row="2"
                                    Grid.Column="1"
                                    Background="Transparent"
                                    DefaultLabelPosition="Right"
                                    Style="{StaticResource PlaylistCommandBarStyle}">
                                    <AppBarButton
                                        Click="Shuffle_Click"
                                        Icon="Shuffle"
                                        IsEnabled="{x:Bind Songs, Converter={StaticResource EnabledConverter}, Mode=OneWay}"
                                        Label="Shuffle"
                                        Style="{StaticResource PlaylistAppBarButtonStyle}"
                                        ToolTipService.ToolTip="Shuffle Playlist" />
                                    <AppBarButton
                                        Click="AddTo_Click"
                                        Icon="Add"
                                        IsEnabled="{x:Bind Songs, Converter={StaticResource EnabledConverter}, Mode=OneWay}"
                                        Label="Add To"
                                        Style="{StaticResource PlaylistAppBarButtonStyle}"
                                        ToolTipService.ToolTip="Add To Playlist" />
                                    <AppBarButton
                                        Click="Rename_Click"
                                        Icon="Edit"
                                        Label="Rename"
                                        Style="{StaticResource PlaylistAppBarButtonStyle}"
                                        ToolTipService.ToolTip="Rename Playlist" />
                                    <AppBarButton
                                        Click="Delete_Click"
                                        Icon="Delete"
                                        Label="Delete"
                                        Style="{StaticResource PlaylistAppBarButtonStyle}"
                                        ToolTipService.ToolTip="Delete Playlist" />
                                    <AppBarButton
                                        Click="More_Click"
                                        Icon="More"
                                        Label="More"
                                        Style="{StaticResource PlaylistAppBarButtonStyle}"
                                        ToolTipService.ToolTip="More Options" />
                                    <CommandBar.SecondaryCommands>
                                        <AppBarButton
                                            HorizontalAlignment="Stretch"
                                            Icon="Pin"
                                            Label="Pin to Start"
                                            ToolTipService.ToolTip="Pin Playlist to the Start Menu" />
                                        <AppBarSeparator />
                                        <AppBarToggleButton Label="Sort By Name" />
                                        <AppBarToggleButton Label="Sort By Artist" />
                                        <AppBarToggleButton Label="Sort By Album" />
                                        <AppBarToggleButton Label="Sort By Duration" />
                                        <AppBarToggleButton Label="Sort By Play Count" />
                                    </CommandBar.SecondaryCommands>
                                </CommandBar>
                            </Grid>
                        </controls:ScrollHeader>
                    </local:PlaylistControl.Header>
                </local:PlaylistControl>
            </DataTemplate>
        </controls:TabView.ItemTemplate>

我正在尝试使用以下方式访问 tab 的 children：

        var i1 = VisualTreeHelper.GetChild(tab, 0);
        var i2 = VisualTreeHelper.GetChild(i1, 0);

然而，i1 是 Grid 而 i2 是 Rectangle。那不是我所期望的。我怎样才能到达 PlaylistControl.Header？

Answer 1

我找到了解决方案。

由于ItemTemplate只会加载一次，其余时间我猜它只是刷新控件绑定的数据，我可以注册控件的Loaded事件我需要

并且在那个Loaded事件中，我可以从参数sender中获取我想要的控件，并将其保存为class变量。那我就可以为所欲为了。