Привязка к ключу ресурса, WPF
У меня есть ResourceDictionary с некоторыми изображениями:
<BitmapImage UriSource="..\Images\Bright\folder-bright.png"
x:Key="FolderItemImage" />
Я создал HierarchicalTemplate для элементов дерева, например:
<HierarchicalDataTemplate ItemsSource="{Binding VisibleChildren}"
DataType="{x:Type st:StructureTreeItem}">
<StackPanel Orientation="Horizontal">
<TextBlock Text="{Binding ImageResourceKey}" />
<Image x:Name="iIcon2" Source="{DynamicResource FolderItemImage}"/>
<Image x:Name="iIcon"
Source="{DynamicResource {Binding ImageResourceKey}}"/>
</StackPanel>
</HierarchicalDataTemplate>
Теперь, когда элемент отображается:
- Текстовые блоки
FolderItemImage - Первое изображение показано
- Второе изображение не показано.
Вся идея состоит в том, чтобы установить изображения элементов, хранящиеся в ресурсах, но техника, представленная выше, к сожалению, не будет работать, и теперь я знаю, почему:
<Image x:Name="iIcon3" Width="16" Height="16" Margin="0, 1, 3, 1" >
<Image.Source>
<DynamicResource ResourceKey="{Binding ImageResourceKey}" />
</Image.Source>
</Image>
Результат:
Произошло необработанное исключение типа "System.Windows.Markup.XamlParseException" в PresentationFramework.dll
Дополнительная информация: "Связывание" не может быть установлено в свойстве "ResourceKey" типа "DynamicResourceExtension". "Связывание" может быть установлено только для свойства DependencyObject объекта DependencyObject.
Поэтому я должен перефразировать мой вопрос: как я могу преобразовать некоторые данные (возможно, ключ ресурса), хранящиеся в модели, в динамический ресурс? Это должен быть динамический ресурс, потому что я уверен, что он может измениться во время выполнения.
4 ответа
Решение
Это не может быть сделано напрямую. Есть и другой способ, связанный с подключенным свойством:
public static class ImageHelper {
private static void SourceResourceKeyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e) {
var element = d as Image;
if (element != null) {
element.SetResourceReference(Image.SourceProperty, e.NewValue);
}
}
public static readonly DependencyProperty SourceResourceKeyProperty = DependencyProperty.RegisterAttached("SourceResourceKey",
typeof(object),
typeof(ImageHelper),
new PropertyMetadata(String.Empty, SourceResourceKeyChanged));
public static void SetSourceResourceKey(Image element, object value) {
element.SetValue(SourceResourceKeyProperty, value);
}
public static object GetSourceResourceKey(Image element) {
return element.GetValue(SourceResourceKeyProperty);
}
}
А потом:
<Image local:ImageHelper.SourceResourceKey="{Binding SomeValue}" />
Я пишу следующее расширение разметки, чтобы разрешить привязку к resourceKey в общем случае
using System;
using System.ComponentModel;
using System.Globalization;
using System.Windows;
using System.Windows.Data;
using System.Windows.Markup;
namespace Mersoft.Mvvm.MarkupExtensions
{
public class ResourceBinding : MarkupExtension
{
#region Helper properties
public static object GetResourceBindingKeyHelper(DependencyObject obj)
{
return (object)obj.GetValue(ResourceBindingKeyHelperProperty);
}
public static void SetResourceBindingKeyHelper(DependencyObject obj, object value)
{
obj.SetValue(ResourceBindingKeyHelperProperty, value);
}
// Using a DependencyProperty as the backing store for ResourceBindingKeyHelper. This enables animation, styling, binding, etc...
public static readonly DependencyProperty ResourceBindingKeyHelperProperty =
DependencyProperty.RegisterAttached("ResourceBindingKeyHelper", typeof(object), typeof(ResourceBinding), new PropertyMetadata(null, ResourceKeyChanged));
static void ResourceKeyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
var target = d as FrameworkElement;
var newVal = e.NewValue as Tuple<object, DependencyProperty>;
if (target == null || newVal == null)
return;
var dp = newVal.Item2;
if (newVal.Item1 == null)
{
target.SetValue(dp, dp.GetMetadata(target).DefaultValue);
return;
}
target.SetResourceReference(dp, newVal.Item1);
}
#endregion
public ResourceBinding()
{
}
public ResourceBinding(string path)
{
this.Path = new PropertyPath(path);
}
public override object ProvideValue(IServiceProvider serviceProvider)
{
var provideValueTargetService = (IProvideValueTarget)serviceProvider.GetService(typeof(IProvideValueTarget));
if (provideValueTargetService == null)
return null;
if (provideValueTargetService.TargetObject != null &&
provideValueTargetService.TargetObject.GetType().FullName == "System.Windows.SharedDp")
return this;
var targetObject = provideValueTargetService.TargetObject as FrameworkElement;
var targetProperty = provideValueTargetService.TargetProperty as DependencyProperty;
if (targetObject == null || targetProperty == null)
return null;
var binding = new Binding();
#region binding
binding.Path = this.Path;
binding.XPath = this.XPath;
binding.Mode = this.Mode;
binding.UpdateSourceTrigger = this.UpdateSourceTrigger;
binding.Converter = this.Converter;
binding.ConverterParameter = this.ConverterParameter;
binding.ConverterCulture = this.ConverterCulture;
if (this.RelativeSource != null)
binding.RelativeSource = this.RelativeSource;
if (this.ElementName != null)
binding.ElementName = this.ElementName;
if (this.Source != null)
binding.Source = this.Source;
binding.FallbackValue = this.FallbackValue;
#endregion
var multiBinding = new MultiBinding();
multiBinding.Converter = HelperConverter.Current;
multiBinding.ConverterParameter = targetProperty;
multiBinding.Bindings.Add(binding);
multiBinding.NotifyOnSourceUpdated = true;
targetObject.SetBinding(ResourceBindingKeyHelperProperty, multiBinding);
return null;
}
#region Binding Members
/// <summary> The source path (for CLR bindings).</summary>
public object Source
{
get;
set;
}
/// <summary> The source path (for CLR bindings).</summary>
public PropertyPath Path
{
get;
set;
}
/// <summary> The XPath path (for XML bindings).</summary>
[DefaultValue(null)]
public string XPath
{
get;
set;
}
/// <summary> Binding mode </summary>
[DefaultValue(BindingMode.Default)]
public BindingMode Mode
{
get;
set;
}
/// <summary> Update type </summary>
[DefaultValue(UpdateSourceTrigger.Default)]
public UpdateSourceTrigger UpdateSourceTrigger
{
get;
set;
}
/// <summary> The Converter to apply </summary>
[DefaultValue(null)]
public IValueConverter Converter
{
get;
set;
}
/// <summary>
/// The parameter to pass to converter.
/// </summary>
/// <value></value>
[DefaultValue(null)]
public object ConverterParameter
{
get;
set;
}
/// <summary> Culture in which to evaluate the converter </summary>
[DefaultValue(null)]
[TypeConverter(typeof(System.Windows.CultureInfoIetfLanguageTagConverter))]
public CultureInfo ConverterCulture
{
get;
set;
}
/// <summary>
/// Description of the object to use as the source, relative to the target element.
/// </summary>
[DefaultValue(null)]
public RelativeSource RelativeSource
{
get;
set;
}
/// <summary> Name of the element to use as the source </summary>
[DefaultValue(null)]
public string ElementName
{
get;
set;
}
#endregion
#region BindingBase Members
/// <summary> Value to use when source cannot provide a value </summary>
/// <remarks>
/// Initialized to DependencyProperty.UnsetValue; if FallbackValue is not set, BindingExpression
/// will return target property's default when Binding cannot get a real value.
/// </remarks>
public object FallbackValue
{
get;
set;
}
#endregion
#region Nested types
private class HelperConverter : IMultiValueConverter
{
public static readonly HelperConverter Current = new HelperConverter();
public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
{
return Tuple.Create(values[0], (DependencyProperty)parameter);
}
public object[] ConvertBack(object value, Type[] targetTypes, object parameter, CultureInfo culture)
{
throw new NotImplementedException();
}
}
#endregion
}
}
использование
<Image Source="{local:ResourceBinding ImageResourceKey}"/>
Я не думаю, что можно использовать динамическое строковое значение в качестве ключа для словаря так, как вы пытаетесь это сделать.
Вам нужно либо сделать Converter который превращается из string в ImageSource или использовать DataTrigger выбирать Source в зависимости от ImageResourceKey
используя конвертер:
в ресурсах:
<local:StringToResource x:Key="StringToResource" />
затем:
<Image x:Name="iIcon" Source="{Binding ImageResourceKey, Converter={StaticResource StringToResource}}"/>
Ваш конвертер может выглядеть так:
public class StringToResource: IValueConverter
{
public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
return Application.Current.FindResource(value as string);
}
public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
throw new NotImplementedException();
}
}
не испытано
public class DynamicResourceBinding : MarkupExtension
{
public DynamicResourceBinding(string path)
{
binding = new Binding(path);
}
#region Binding Members
public PropertyPath Path
{
get { return binding.Path; }
set { binding.Path = value; }
}
public string XPath
{
get { return binding.XPath; }
set { binding.XPath = value; }
}
[DefaultValue(BindingMode.Default)]
public BindingMode Mode
{
get { return binding.Mode; }
set { binding.Mode = value; }
}
[DefaultValue(UpdateSourceTrigger.Default)]
public UpdateSourceTrigger UpdateSourceTrigger
{
get { return binding.UpdateSourceTrigger; }
set { binding.UpdateSourceTrigger = value; }
}
public IValueConverter Converter
{
get { return binding.Converter; }
set { binding.Converter = value; }
}
public object ConverterParameter
{
get { return binding.ConverterParameter; }
set { binding.ConverterParameter = value; }
}
[TypeConverter(typeof(CultureInfoIetfLanguageTagConverter))]
public CultureInfo ConverterCulture
{
get { return binding.ConverterCulture; }
set { binding.ConverterCulture = value; }
}
public object Source
{
get { return binding.Source; }
set { binding.Source = value; }
}
public string ElementName
{
get { return binding.ElementName; }
set { binding.ElementName = value; }
}
public RelativeSource RelativeSource
{
get { return binding.RelativeSource; }
set { binding.RelativeSource = value; }
}
public object FallbackValue
{
get { return binding.FallbackValue; }
set { binding.FallbackValue = value; }
}
private readonly Binding binding;
#endregion Binding Members
public override object ProvideValue(IServiceProvider serviceProvider)
{
var provideValueTarget = serviceProvider.GetService(typeof(IProvideValueTarget)) as IProvideValueTarget;
if (provideValueTarget != null)
{
var targetObject = provideValueTarget.TargetObject as FrameworkElement;
if (targetObject != null)
{
var targetProperty = provideValueTarget.TargetProperty as DependencyProperty;
if (targetProperty != null)
{
targetObject.SetBinding(EnsureResourceKeyProperty(targetProperty), binding);
}
}
}
return null;
}
private static readonly object locker = new object();
public static DependencyProperty EnsureResourceKeyProperty(DependencyProperty targetProperty)
{
DependencyProperty resourceKeyProperty;
lock (locker)
{
if (!DirectMap.TryGetValue(targetProperty, out resourceKeyProperty))
{
resourceKeyProperty = RegisterResourceKeyProperty(targetProperty);
DirectMap.Add(targetProperty, resourceKeyProperty);
ReverseMap.Add(resourceKeyProperty, targetProperty);
}
}
return resourceKeyProperty;
}
private static DependencyProperty RegisterResourceKeyProperty(DependencyProperty targetProperty)
{
return DependencyProperty.RegisterAttached(targetProperty.Name + "_ResourceKey", typeof(object), typeof(DynamicResourceBinding),
new PropertyMetadata(ResourceKeyChanged));
}
private static void ResourceKeyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
var fe = d as FrameworkElement;
if (fe != null)
{
lock (locker)
{
DependencyProperty targetProperty;
if (ReverseMap.TryGetValue(e.Property, out targetProperty))
{
fe.SetResourceReference(targetProperty, e.NewValue);
}
}
}
}
private static readonly Dictionary<DependencyProperty, DependencyProperty> DirectMap = new Dictionary<DependencyProperty, DependencyProperty>();
private static readonly Dictionary<DependencyProperty, DependencyProperty> ReverseMap = new Dictionary<DependencyProperty, DependencyProperty>();
}
использование