Question

我有一个UWP应用程序，在其页面中我显示了一个项目列表。这些项不是同一个类，但是，这些类之间有许多相同的属性。因此，我更喜欢使用一个UserControl，而不是使用多个UserControl并使用TemplateSelector。但数据不会像我预期的那样显示出来。

我在这里给你一个例子。

我有一个名为 Base 的课程：

public class Base
{
    public int Id { get; set; }
    public string Name { get; set; }
}

和2个派生自它的类：

public interface ILiker
{
    int LikeCount { get; set; }
    bool? IsLiked { get; set; }
}

public class Liker : Base, ILiker
{
    public int LikeCount { get; set; }
    public bool? IsLiked { get; set; }
}

public interface IFollower
{
    int FollowCount { get; set; }
    bool? IsFollowed { get; set; }
}

public class Follower : Base, IFollower
{
    public int FollowCount { get; set; }
    public bool? IsFollowed { get; set; }
}

我的列表项类型为 Liker 或关注者，因此我实现了另一个类来统一它们：

public class Unified
{
    private Type _type;

    public Unified(Follower item)
    {
        _type = item.GetType();
        BaseInfo = (Base)item;
        FollowerInfo = (IFollower)item;
    }

    public Unified(Liker item)
    {
        _type = item.GetType();
        BaseInfo = (Base)item;
        LikerInfo = (ILiker)item;
    }

    public Base BaseInfo { get; set; }
    public ILiker LikerInfo { get; set; }
    public IFollower FollowerInfo { get; set; }

    public new Type GetType()
    {
        return _type;
    }
}

有时我需要在一个列表项中的2个不同位置显示 Base 类，因为我创建了一个单独的 BaseTemplate ：

BaseTemplate.xaml ：

<UserControl ...>
    <StackPanel VerticalAlignment="Top">
        <TextBlock FontSize="15" Foreground="Black" Text="{x:Bind Data.Name}" />
        <TextBlock FontSize="10" Foreground="Gray" Text="{x:Bind Data.Id}" Margin="5" />
    </StackPanel>
</UserControl>

BaseTemplate.xaml.cs ：

public sealed partial class BaseTemplate : UserControl
{
    public Base Data
    {
        get { return (Base)GetValue(DataProperty); }
        set { SetValue(DataProperty, value); }
    }

    // Using a DependencyProperty as the backing store for Data.  This enables animation, styling, binding, etc...
    public static readonly DependencyProperty DataProperty =
        DependencyProperty.Register("Data", typeof(Base), typeof(BaseTemplate), new PropertyMetadata(null));


    public BaseTemplate()
    {
        this.InitializeComponent();
    }
}

还为我的列表项创建了一个模板：

UnifiedTemplate.xaml ：

<UserControl ...>
    <Grid VerticalAlignment="Top" Padding="{x:Bind Padding}" BorderBrush="{x:Bind BorderBrush}" BorderThickness="{x:Bind BorderThickness}" Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">

        <Grid.RowDefinitions>
            <RowDefinition Height="Auto" />
            <RowDefinition Height="Auto" />
        </Grid.RowDefinitions>

        <Grid.ColumnDefinitions>
            <ColumnDefinition />
            <ColumnDefinition Width="Auto" />
        </Grid.ColumnDefinitions>

        <local:BaseTemplate Data="{x:Bind Data.BaseInfo}" />

        <Button
            Grid.Row="0"
            Grid.Column="1"
            Content="{x:Bind Data.BaseInfo}">
            <Button.ContentTemplate>
                <DataTemplate>
                    <local:BaseTemplate Data="{Binding}" />
                </DataTemplate>
            </Button.ContentTemplate>
        </Button>

        <StackPanel Grid.Row="1" Grid.ColumnSpan="2" Background="SlateGray">

            <RichTextBlock x:Name="LikeBlock" x:DeferLoadStrategy="Lazy">
                <Paragraph>
                    <InlineUIContainer>
                        <TextBlock Text="Like Count: " />
                    </InlineUIContainer>
                    <Run Text="{x:Bind Data.LikerInfo.LikeCount}" />
                    <LineBreak />
                    <InlineUIContainer>
                        <ToggleButton Content="Like" Tapped="OnLikeTapped" IsChecked="{x:Bind Data.LikerInfo.IsLiked}" />
                    </InlineUIContainer>
                </Paragraph>
            </RichTextBlock>

            <RichTextBlock x:Name="FollowBlock" x:DeferLoadStrategy="Lazy">
                <Paragraph>
                    <InlineUIContainer>
                        <TextBlock Text="Follow Count: " />
                    </InlineUIContainer>
                    <Run Text="{x:Bind Data.FollowerInfo.FollowCount}" />
                    <LineBreak />
                    <InlineUIContainer>
                        <ToggleButton Content="Follow" Tapped="OnFollowTapped" IsChecked="{x:Bind Data.FollowerInfo.IsFollowed}" />
                    </InlineUIContainer>
                </Paragraph>
            </RichTextBlock>

        </StackPanel>

    </Grid>
</UserControl>

UnifiedTemplate.xaml.cs ：

public sealed partial class UnifiedTemplate : UserControl
{
    public Unified Data
    {
        get { return (Unified)GetValue(DataProperty); }
        set { SetValue(DataProperty, value); }
    }

    // Using a DependencyProperty as the backing store for Data.  This enables animation, styling, binding, etc...
    public static readonly DependencyProperty DataProperty =
        DependencyProperty.Register("Data", typeof(Unified), typeof(UnifiedTemplate), new PropertyMetadata(null, OnChanged));

    private static void OnChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        var that = d as UnifiedTemplate;

        if (that == null || e.NewValue == null) return;

        var data = (Unified) e.NewValue;

        if (data.GetType() == typeof(Liker))
        {
            that.FindName(nameof(LikeBlock));
        }
        else
        {
            that.FindName(nameof(FollowBlock));
        }
    }


    public UnifiedTemplate()
    {
        this.InitializeComponent();
    }

    private void OnLikeTapped(object sender, TappedRoutedEventArgs e) {...}
    private void OnFollowTapped(object sender, TappedRoutedEventArgs e) {...}
}

当我运行应用程序时，基类类数据根本不会显示。我的做法有什么问题？对于这个长期的问题，对不起，这是我能给出的最简单的例子。

修改：Here是一个非常类似的项目，可以重现问题。

UWP - UserControl无法正确显示给定数据

0 个答案: