Question

我正在尝试使用Silverlight DataStateBehavior，它在大多数情况下工作正常，我单击一个按钮，将视图模型中的“Selected”属性设置为false或true。然后，DataStateBehavior告诉VisualStateManager进入相关状态。

像这样：

   <Button...>
   <i:Interaction.Behaviors>
             <id:DataStateBehavior Binding="{Binding Selected}" Value="True" TrueState="SelectedVisualState" FalseState="DeselectedVisualState"/>
          </i:Interaction.Behaviors>
   </Button>

以上工作正常。我试图做的是让它在应用程序加载时设置正确的状态，如果我将视图模型上的'Selected'属性设置为true，默认情况下我不会看到UI中的任何更改我单击按钮更改viewmodel属性。

我知道有几个涉及DataState的类，包括：

BindingListener.cs
ConverterHelper.cs
DataStateBehavior.cs
DataStateSwitchBehavior.cs
DataTrigger.cs

任何线索都会很好，感谢

Answer 1

我实际上要添加我刚刚尝试的第二个答案，并且似乎更清晰，因为它可以在XAML中完成并且没有自定义行为。我将留下另一个答案作为替代解决方案的参考，因为它们都有效。

<i:Interaction.Triggers>
    <i:EventTrigger EventName="Loaded">
        <ic:GoToStateAction StateName="SelectedVisualState"/>
    </i:EventTrigger>
</i:Interaction.Triggers>

您只需添加对作为Blend SDK一部分的Microsoft.Expression.Interactions程序集的引用。

xmlns:ic="clr-namespace:Microsoft.Expression.Interactivity.Core;assembly=Microsoft.Expression.Interactions"

Answer 2

尝试DataStateBehavior类的此扩展。加载目标元素时，将评估DataStateBehavior，就好像属性已更新一样。

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;

namespace Gusdor.Wpf
{
    /// <summary>
    /// Fix for data state behavior. Behavior will trigger transitions when target element loads.
    /// </summary>
    class DataStateBehaviorFix: Microsoft.Expression.Interactivity.Core.DataStateBehavior
    {
        public bool UseTransitionsOnLoad { get; set; }

        protected override void OnAttached()
        {
            base.OnAttached();

            AssociatedObject.Loaded += AssociatedObject_Loaded;
        }

        protected override void OnDetaching()
        {
            base.OnDetaching();

            AssociatedObject.Loaded -= AssociatedObject_Loaded;
        }

        void AssociatedObject_Loaded(object sender, System.Windows.RoutedEventArgs e)
        {
            Evaluate();
        }

        void Evaluate()
        {
            if (Value == null)
            {
                GotoState(Binding == null, this.AssociatedObject);
            }
            else GotoState(Value.Equals(Binding), this.AssociatedObject);
        }

        /// <summary>
        /// Attempts to change to the named state. Walks up tree to first match.
        /// </summary>
        /// <param name="flag"></param>
        /// <param name="element"></param>
        void GotoState(bool flag, FrameworkElement element)
        {          
            string stateName = flag ? TrueState : FalseState;

            if (HasState(element, stateName))
            {
                bool ret = System.Windows.VisualStateManager.GoToElementState(element, stateName, UseTransitionsOnLoad);
            }
            else if (element.Parent as FrameworkElement != null)
                GotoState(flag, element.Parent as FrameworkElement);
        }
        /// <summary>
        /// Checks if an element has the state named
        /// </summary>
        /// <param name="element"></param>
        /// <param name="stateName"></param>
        /// <returns></returns>
        bool HasState(FrameworkElement element, string stateName)
        {
            var groups = Microsoft.Expression.Interactivity.VisualStateUtilities.GetVisualStateGroups(element).Cast<VisualStateGroup>();

            return groups.Any(p => p.States.Cast<VisualState>().Any(s => s.Name == stateName));
        }
    }
}

Answer 3

我解决此问题的一种方法是创建一个可以添加到控件中的行为，以便在加载时将其置于初始可视状态。这是一个简单的例子：

public class InitialVisualStateBehavior : Behavior<Control>
{
    public static readonly DependencyProperty InitialStateProperty = DependencyProperty.Register(
        "InitialState",
        typeof(string),
        typeof(InitialVisualStateBehavior),
        null);

    public string InitialState
    {
        get { return (string)GetValue(InitialStateProperty); }
        set { SetValue(InitialStateProperty, value); }
    }

    protected override void OnAttached()
    {
        base.OnAttached();

        if (this.AssociatedObject != null)
        {
            this.AssociatedObject.Loaded += new RoutedEventHandler(AssociatedObject_Loaded);
        }
    }

    protected override void OnDetaching()
    {
        base.OnDetaching();

        if (this.AssociatedObject != null)
        {
            this.AssociatedObject.Loaded -= AssociatedObject_Loaded;
        }
    }

    private void AssociatedObject_Loaded(object sender, RoutedEventArgs e)
    {
        VisualStateManager.GoToState(this.AssociatedObject, this.InitialState, false);
    }
}

然后，您只需将该行为添加到XAML中的UserControl级别：

<i:Interaction.Behaviors>
    <myi:InitialVisualStateBehavior InitialState="SelectedVisualState" />
</i:Interaction.Behaviors>

您也可以轻松地修改它以接受逗号分隔的初始状态列表，如果您需要在加载后将控件置于一堆不同的互斥状态，则可以拆分并循环。

这也可以重构为TriggerAction，你可以触发控件的Loaded事件，我不知道哪种方式会更清晰。

Silverlight DataStateBehavior，未使用初始值

3 个答案: