c# - WPF/Windows 8 应用程序 DataTemplate 数据绑定(bind)事件

Question

我在 ListView 的 DataTemplate 中有一个 RichTextBox 控件。我的想法是，我想在绑定(bind)时将 Runs/InlineUIElements/images 等动态添加到 Listview 中的富文本框。问题是没有 ondatabinding 或类似事件。我尝试了 RichTextBox 的 Loaded 事件，但似乎 WPF 重用了控件，因此当我滚动时内容被弄乱了(以错误的顺序放置错误的内容，因为加载事件在滚动期间触发)。我还应该提到，通过手动将行添加到 ListView.Items 集合，绑定(bind)到 ListView 是在代码隐藏中进行的。

相关标记

 <ListView Background="#F7F7F7" HorizontalAlignment="Stretch" Foreground="Black" x:Name="chatPane" Grid.Row="1" 
                  ScrollViewer.HorizontalScrollBarVisibility="Disabled" HorizontalContentAlignment="Stretch" SelectionMode="Multiple"
              ItemTemplateSelector="{StaticResource messageTypeDataTemplateSelector}" SelectionChanged="ChatPane_OnSelectionChanged">
        </ListView>

<common:MessageTypeDataTemplateSelector 
        TextMessageTemplate="{StaticResource TextMessage}" 
        EnterMessageTemplate="{StaticResource EnterMessage}" 
        ExitMessageTemplate="{StaticResource ExitMessage}"
        TimestampMessageTemplate="{StaticResource TimestampMessage}"
        ImageMessageTemplate="{StaticResource ImageMessage}"
        x:Key="messageTypeDataTemplateSelector" />

<DataTemplate x:Key="TextMessage">
        <Grid Grid.ColumnSpan="3" RowSpan="1">
            <Grid.ColumnDefinitions>
                <ColumnDefinition  Width="Auto"/>
                <ColumnDefinition Width=".5*"/>
                <ColumnDefinition Width="70*"/>
            </Grid.ColumnDefinitions>
            <TextBlock Text="{Binding UserName}" Visibility="{Binding Source={StaticResource chatSettings}, Path=HideAvatars, Converter={StaticResource booleanToVisibility}}" FontWeight="Bold" TextAlignment="Right" Grid.Column="0" Width="150" />
            <Image VerticalAlignment="Top" Source="{Binding AvatarUrl}" Visibility="{Binding Source={StaticResource chatSettings}, Path=ShowAvatars, Converter={StaticResource booleanToVisibility}}" Grid.Column="0" Width="60" Margin="0,0,10,0" />
            <TextBlock Text=" : " Visibility="{Binding Source={StaticResource chatSettings}, Path=HideAvatars, Converter={StaticResource booleanToVisibility}}" Grid.Column="1"  />
            <RichTextBlock Loaded="FrameworkElement_OnLoaded" TextWrapping="Wrap" Grid.Column="2" />
        </Grid>
    </DataTemplate>

Answer 1

你完全正确。 WinRT 中没有 OnDataBinding 事件。这个想法怎么样:

为 RichTextBlock (http://msdn.microsoft.com/en-us/library/ms749011(v=vs.110).aspx) 创建一个 AttachedProperty，然后将您的项目绑定(bind)到它。当您注册附加属性时，在 FrameworkPropertyMetadata 中，您可以指定一个 PropertyChangedCallback，只要附加属性的值发生变化，它就会触发。像这样:

现在，为确保它有效，请在您当前的 .xaml.cs 文件中执行以下操作:

public static readonly DependencyProperty RichTextBlockItemProperty = DependencyProperty.RegisterAttached(
  "RichTextBlockItem",
  typeof(object),
  typeof(RichTextBlock),
  new PropertyMetadata(null, RichTextBlockItemChanged)
);

// Don't forget this!
public static object GetRichTextBlockItem(DependencyObject obj)
{
    return (object)obj.GetValue(RichTextBlockItemProperty);
}

// And this!
public static void SetRichTextBlockItem(DependencyObject obj, object value)
{
   obj.SetValue(RichTextBlockItemProperty, value);
}

public void RichTextBlockItemChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
    // Here you can do whatever you wish. This method will fire when the item is bound.
    // d is the RichTextBlock object.
    // e.NewValue is the value that was just bound.
    // So, from here you can dynamically add your Runs/Images/etc
}

然后在您的 .xaml 文件中确保添加一个本地命名空间，这样您就可以执行此操作:

<Page .... xmlns:local="using:CurrentXamlPageNamespace".../>

<DataTemplate x:Key="TextMessage">
    <Grid Grid.ColumnSpan="3" RowSpan="1">
        <!-- I got rid of the other xaml just to hightlight my answer. But you still need it. -->
        <RichTextBlock local:RichTextBlock.RichTextBlockItem="{Binding}" TextWrapping="Wrap" Grid.Column="2" />
    </Grid>
</DataTemplate>