[英]How to set VisualState INITIALIZATION via data binding in XAML, WPF
我想知道如何使用XAML来用正确的VisualState初始化UI元素。 不附带代码 。 因为我知道如何使用C#代码。
我的UI元素的XAML如下所示:
<Border x:Name="PART_Border" >
<VisualStateManager.VisualStateGroups>
<VisualStateGroup x:Name="CriticalnessStates">
<VisualState x:Name="NonCritical"/>
<VisualState x:Name="Critical"/>
</VisualStateGroup>
</VisualStateManager.VisualStateGroups>
<i:Interaction.Triggers>
<ei:DataTrigger Binding="{Binding IsCritical}" Value="False">
<ei:GoToStateAction StateName="NonCritical"/>
</ei:DataTrigger>
<ei:DataTrigger Binding="{Binding IsCritical}" Value="True">
<ei:GoToStateAction StateName="Critical"/>
</ei:DataTrigger>
</i:Interaction.Triggers>
</Border>
在加载UI元素后设置IsCritical属性时,它可以完美工作,但是问题是,我需要该元素才能加载正确的 VisualState; 我的意思是,
IsCritical = true =>处于临界状态的元素加载
IsCritical = false =>处于非关键状态的元素加载
通过文件后面的C#代码是可行的,您可以为元素编写一个加载的事件处理程序,该处理程序通过检查相应的DataContext属性来设置可视状态。 我想知道如何使用纯XAML做到这一点。
顺便说一下, ei和i指向这些XML名称空间:
xmlns:ei =“ http://schemas.microsoft.com/expression/2010/interactivity” xmlns:ei =“ http://schemas.microsoft.com/expression/2010/interactions”
谢谢。
我实现了这个Behavior类:
using System;
using System.Windows;
using System.Collections.Generic;
using System.Windows.Interactivity;
using System.Windows.Markup;
[ContentProperty("Conditions")]
public class VisualStateInitializer : Behavior<FrameworkElement>
{
private bool _useTransitions = true;
public bool UseTransitions
{
get { return _useTransitions; }
set { _useTransitions = value; }
}
public List<VisualStateCondition> Conditions { get; set; }
public VisualStateInitializer()
{
Conditions = new List<VisualStateCondition>();
}
protected override void OnAttached()
{
base.OnAttached();
AssociatedObject.Loaded += AssociatedObject_Loaded;
}
protected override void OnDetaching()
{
base.OnDetaching();
}
private void AssociatedObject_Loaded(object sender, RoutedEventArgs e)
{
if (AssociatedObject.DataContext == null)
return;
foreach (var item in Conditions)
{
var dataContextType = AssociatedObject.DataContext.GetType();
System.Reflection.PropertyInfo propertyInfo;
object value = null;
var properties = item.PropertyName.Split('.');
if (properties.Length > 1)
{
for (int i = 0; i < properties.Length; i++)
{
if(value != null)
{
dataContextType = value.GetType();
propertyInfo = dataContextType.GetProperty(properties[i]);
value = propertyInfo.GetValue(value);
}
else
{
propertyInfo = dataContextType.GetProperty(properties[i]);
value = propertyInfo.GetValue(AssociatedObject.DataContext);
}
}
}
else
{
value = AssociatedObject.DataContext.GetType().GetProperty(item.PropertyName).GetValue(AssociatedObject.DataContext);
}
if (value != null && value.Equals(item.Value))
VisualStateManager.GoToElementState(AssociatedObject, item.DesiredState, UseTransitions);
}
}
}
而且VisualStateCondition类是这样的:
public class VisualStateCondition
{
/// <summary>
/// The PropertyName to look for in the associated object's <see cref="FrameworkElement.DataContext"/>.
/// </summary>
public string PropertyName { get; set; }
/// <summary>
/// The Value to check for equality.
/// </summary>
public object Value { get; set; }
/// <summary>
/// The <see cref="VisualState.Name"/> that is desired for the condition.
/// </summary>
public string DesiredState { get; set; }
}
在正确的初始状态下初始化View类所需要做的就是定义VisualStateConditions,如下所示:
注意=> xaml中的“ i”命名空间是指BlendSdk xmlns的“ System.Windows.Interactivity”:i =“ http://schemas.microsoft.com/expression/2010/interactivity”
<Border>
<VisualStateManager.VisualStateGroups>
<VisualStateGroup x:Name="CriticalnessStates">
<VisualState x:Name="NonCritical"/>
<VisualState x:Name="Critical"/>
</VisualStateGroup>
</VisualStateManager.VisualStateGroups>
<i:Interaction.Behaviors>
<viewHelpers:VisualStateInitializer>
<viewHelpers:VisualStateCondition PropertyName="IsCritical" DesiredState="Critical">
<viewHelpers:VisualStateCondition.Value>
<system:Boolean>
True
</system:Boolean>
</viewHelpers:VisualStateCondition.Value>
</viewHelpers:VisualStateCondition>
<viewHelpers:VisualStateCondition PropertyName="IsCritical" DesiredState="NonCritical">
<viewHelpers:VisualStateCondition.Value>
<system:Boolean>
False
</system:Boolean>
</viewHelpers:VisualStateCondition.Value>
</viewHelpers:VisualStateCondition>
</viewHelpers:VisualStateInitializer>
</i:Interaction.Behaviors>
</border>
其中ViewHelpers是我的VisualStateInitializer和VisualStateCondition类的名称空间。 谁能建议一个更好的方法?
UPDATE 1 =>编辑属性值检索,以便我们可以传递嵌套属性,例如:
<viewHelpers:VisualStateCondition PropertyName="X.Y.NestedProperty"
Value="False"
DesiredState="StateForNestedProperty"/>
IsCritical
是一种源属性,应该在视图模型或控件本身中通过编程方式实现和设置。 因此,应在视图模型中或在实现属性的任何位置设置默认值。
Style
或DataTrigger
无法设置视图模型属性的值。
另外,应该是控件的实现,该控件应定义控件所在的视觉状态。您可以通过在控件类中以编程方式调用VisualStateManager.GoToState
实现此目的。
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