如何在样式中使用附加属性

Question

我已经在ButtonStyle中创建了一个图像。现在我已经创建了一个附加属性，这样我就可以为该图像设置源。应该是直截了当的，但我被它困住了。

这是我的缩短ButtonStyle:

<Style x:Key="ToolBarButtonStyle"
        TargetType="Button">
    ...
    <Image x:Name="toolbarImage"
            Source="{TemplateBinding PrismExt:ImageSourceAttachable:ImageSource}"
            Width="48"
            Height="48" />
    ...
</Style>

这是附加的属性定义，请注意，我不知道如何修复回调，因为dependencyproperty似乎是按钮而不是图像。并且Button不会在它的样式中暴露我的图像。其棘手。

namespace SalesContactManagement.Infrastructure.PrismExt
{
    public class ImgSourceAttachable
    {
        public static void SetImgSource(DependencyObject obj, string imgSource)
        {
            obj.SetValue(ImgSourceProperty, imgSource);
        }
        public static string GetImgSource(DependencyObject obj)
        {
            return obj.GetValue(ImgSourceProperty).ToString();
        }
        // Using a DependencyProperty as the backing store for MyProperty.  This enables animation, styling, binding, etc...
        public static readonly DependencyProperty ImgSourceProperty =
            DependencyProperty.RegisterAttached("ImgSource", typeof(string), typeof(ImgSourceAttachable), new PropertyMetadata(Callback));
        private static void Callback(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            //((Button)d).Source = new BitmapImage(new Uri(Application.Current.Host.Source, e.NewValue.ToString()));
        }
    }
}

这是我如何在XAML中设置图像源:

<Button PrismExt:ImgSourceAttachable.ImgSource="./Images/New.png"
        Style="{StaticResource ToolBarButtonStyle}" />

有什么想法吗?多谢,

Answer 1

如何在样式中设置附加属性

<Style x:Key="ToolBarButtonStyle" TargetType="Button">
    <Setter Property="PrismExt:ImgSourceAttachable.ImgSource"
            Value="./Images/New.png"/>
    <!--...-->
</Style>

当绑定到附加属性时，Path应该在括号内，所以尝试使用RelativeSource binding with TemplatedParent来代替

<Setter Property="Template">
    <Setter.Value>
        <ControlTemplate TargetType="Button">
            <Image x:Name="toolbarImage"
                    Source="{Binding RelativeSource={RelativeSource TemplatedParent},
                                    Path=(PrismExt:ImgSourceAttachable.ImgSource)}"
                    Width="48"
                    Height="48">
            </Image>
        </ControlTemplate>
    </Setter.Value>
</Setter>

编辑:上面的代码在WPF中工作，在Silverlight中Image显示在运行时，但它在设计器中异常失败。您可以在PropertyChangedCallback中使用以下代码来获取Image作为变通方法

private static void Callback(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
    Button button = d as Button;
    Image image = GetVisualChild<Image>(button);
    if (image == null)
    {
        RoutedEventHandler loadedEventHandler = null;
        loadedEventHandler = (object sender, RoutedEventArgs ea) =>
        {
            button.Loaded -= loadedEventHandler;
            button.ApplyTemplate();
            image = GetVisualChild<Image>(button);
            // Here you can use the image
        };
        button.Loaded += loadedEventHandler;
    }
    else
    {
        // Here you can use the image
    }
}
private static T GetVisualChild<T>(DependencyObject parent) where T : DependencyObject
{
    T child = default(T);
    int numVisuals = VisualTreeHelper.GetChildrenCount(parent);
    for (int i = 0; i < numVisuals; i++)
    {
        DependencyObject v = (DependencyObject)VisualTreeHelper.GetChild(parent, i);
        child = v as T;
        if (child == null)
        {
            child = GetVisualChild<T>(v);
        }
        if (child != null)
        {
            break;
        }
    }
    return child;
}