VisualStateManager不像宣传的那样工作

Question

以下问题一直困扰着我好几天,但我只能将它提炼到最简单的形式.考虑以下XAML:

<Window x:Class="VSMTest.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="350" Width="525">

    <Window.Resources>
        <Style TargetType="CheckBox">
            <Setter Property="Margin" Value="3"/>
            <Setter Property="Template">
                <Setter.Value>
                    <ControlTemplate TargetType="CheckBox">
                        <Grid x:Name="Root">
                            <Grid.Background>
                                <SolidColorBrush x:Name="brush" Color="White"/>
                            </Grid.Background>

                            <VisualStateManager.VisualStateGroups>
                                <VisualStateGroup Name="CheckStates">
                                    <VisualStateGroup.Transitions>
                                        <VisualTransition To="Checked" GeneratedDuration="00:00:03">
                                            <Storyboard Name="CheckingStoryboard">
                                                <ColorAnimationUsingKeyFrames Storyboard.TargetName="brush" Storyboard.TargetProperty="Color">
                                                    <DiscreteColorKeyFrame KeyTime="0" Value="LightGreen"/>
                                                </ColorAnimationUsingKeyFrames>
                                            </Storyboard>
                                        </VisualTransition>

                                        <VisualTransition To="Unchecked" GeneratedDuration="00:00:03">
                                            <Storyboard Name="UncheckingStoryboard">
                                                <ColorAnimationUsingKeyFrames Storyboard.TargetName="brush" Storyboard.TargetProperty="Color">
                                                    <DiscreteColorKeyFrame KeyTime="0" Value="LightSalmon"/>
                                                </ColorAnimationUsingKeyFrames>
                                            </Storyboard>
                                        </VisualTransition>
                                    </VisualStateGroup.Transitions>

                                    <VisualState Name="Checked">
                                        <Storyboard Name="CheckedStoryboard" Duration="0">
                                            <ColorAnimationUsingKeyFrames Storyboard.TargetName="brush" Storyboard.TargetProperty="Color">
                                                <DiscreteColorKeyFrame KeyTime="0" Value="Green"/>
                                            </ColorAnimationUsingKeyFrames>
                                        </Storyboard>
                                    </VisualState>

                                    <VisualState Name="Unchecked">
                                        <Storyboard Name="UncheckedStoryboard" Duration="0">
                                            <ColorAnimationUsingKeyFrames Storyboard.TargetName="brush" Storyboard.TargetProperty="Color">
                                                <DiscreteColorKeyFrame KeyTime="0" Value="Red"/>
                                            </ColorAnimationUsingKeyFrames>
                                        </Storyboard>
                                    </VisualState>
                                </VisualStateGroup>
                            </VisualStateManager.VisualStateGroups>

                            <ContentPresenter/>
                        </Grid>
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </Style>
    </Window.Resources>

    <StackPanel>
        <CheckBox x:Name="cb1">Check Box 1</CheckBox>
        <CheckBox x:Name="cb2">Check Box 2</CheckBox>
        <CheckBox x:Name="cb3">Check Box 3</CheckBox>
    </StackPanel>
</Window>

它只是重新模板CheckBox控件,使其背景依赖于其状态:

• 选中=绿色
• 未选中=红色
• 检查(转换)=浅绿色
• 取消选中(转换)=浅红色

因此,当您选中其中一个复选框时,您希望它在短时间内变为浅绿色,然后变为绿色.同样,当取消选中时,您会希望它在短时间内变为浅红色,然后变为红色.

它通常就是这样.但不总是.

玩这个程序的时间足够长(我可以在大约30秒内得到它),你会发现过渡动画有时会在视觉状态下胜过它.也就是说,复选框在选中时将继续显示为浅绿色,或在未选中时显示为浅红色.这是一个屏幕截图,说明了我的意思,在过渡配置为3秒后取得好成绩:

发生这种情况时,并不是因为控件未成功转换到目标状态.它声称处于正确的状态.我通过在调试器中检查以下内容来验证这一点(针对上面屏幕截图中记录的特定情况):

var vsgs = VisualStateManager.GetVisualStateGroups(VisualTreeHelper.GetChild(this.cb2, 0) as FrameworkElement);
var vsg = vsgs[0];
// this is correctly reported as "Unselected"
var currentState = vsg.CurrentState.Name;

如果我启用动画跟踪,转换成功完成后会得到以下输出:

System.Windows.Media.Animation Start: 1 : Storyboard has begun; Storyboard='System.Windows.Media.Animation.Storyboard'; Storyboard.HashCode='44177654'; Storyboard.Type='System.Windows.Media.Animation.Storyboard'; StoryboardName='UncheckedStoryboard'; TargetElement='System.Windows.Controls.Grid'; TargetElement.HashCode='41837403'; TargetElement.Type='System.Windows.Controls.Grid'; NameScope='<null>'
System.Windows.Media.Animation Stop: 1 : 
System.Windows.Media.Animation Start: 1 : Storyboard has begun; Storyboard='System.Windows.Media.Animation.Storyboard'; Storyboard.HashCode='6148812'; Storyboard.Type='System.Windows.Media.Animation.Storyboard'; StoryboardName='UncheckedStoryboard'; TargetElement='System.Windows.Controls.Grid'; TargetElement.HashCode='8261103'; TargetElement.Type='System.Windows.Controls.Grid'; NameScope='<null>'
System.Windows.Media.Animation Stop: 1 : 
System.Windows.Media.Animation Start: 1 : Storyboard has begun; Storyboard='System.Windows.Media.Animation.Storyboard'; Storyboard.HashCode='36205315'; Storyboard.Type='System.Windows.Media.Animation.Storyboard'; StoryboardName='UncheckedStoryboard'; TargetElement='System.Windows.Controls.Grid'; TargetElement.HashCode='18626439'; TargetElement.Type='System.Windows.Controls.Grid'; NameScope='<null>'
System.Windows.Media.Animation Stop: 1 : 
System.Windows.Media.Animation Start: 3 : Storyboard has been removed; Storyboard='System.Windows.Media.Animation.Storyboard'; Storyboard.HashCode='44177654'; Storyboard.Type='System.Windows.Media.Animation.Storyboard'; StoryboardName='UncheckedStoryboard'; TargetElement='System.Windows.Controls.Grid'; TargetElement.HashCode='41837403'; TargetElement.Type='System.Windows.Controls.Grid'
System.Windows.Media.Animation Stop: 3 : 
System.Windows.Media.Animation Start: 1 : Storyboard has begun; Storyboard='System.Windows.Media.Animation.Storyboard'; Storyboard.HashCode='36893403'; Storyboard.Type='System.Windows.Media.Animation.Storyboard'; StoryboardName='CheckingStoryboard'; TargetElement='System.Windows.Controls.Grid'; TargetElement.HashCode='41837403'; TargetElement.Type='System.Windows.Controls.Grid'; NameScope='<null>'
System.Windows.Media.Animation Stop: 1 : 
System.Windows.Media.Animation Start: 1 : Storyboard has begun; Storyboard='System.Windows.Media.Animation.Storyboard'; Storyboard.HashCode='49590434'; Storyboard.Type='System.Windows.Media.Animation.Storyboard'; StoryboardName='<null>'; TargetElement='System.Windows.Controls.Grid'; TargetElement.HashCode='41837403'; TargetElement.Type='System.Windows.Controls.Grid'; NameScope='<null>'
System.Windows.Media.Animation Stop: 1 : 
System.Windows.Media.Animation Start: 3 : Storyboard has been removed; Storyboard='System.Windows.Media.Animation.Storyboard'; Storyboard.HashCode='36893403'; Storyboard.Type='System.Windows.Media.Animation.Storyboard'; StoryboardName='CheckingStoryboard'; TargetElement='System.Windows.Controls.Grid'; TargetElement.HashCode='41837403'; TargetElement.Type='System.Windows.Controls.Grid'
System.Windows.Media.Animation Stop: 3 : 
System.Windows.Media.Animation Start: 3 : Storyboard has been removed; Storyboard='System.Windows.Media.Animation.Storyboard'; Storyboard.HashCode='49590434'; Storyboard.Type='System.Windows.Media.Animation.Storyboard'; StoryboardName='<null>'; TargetElement='System.Windows.Controls.Grid'; TargetElement.HashCode='41837403'; TargetElement.Type='System.Windows.Controls.Grid'
System.Windows.Media.Animation Stop: 3 : 
System.Windows.Media.Animation Start: 1 : Storyboard has begun; Storyboard='System.Windows.Media.Animation.Storyboard'; Storyboard.HashCode='16977025'; Storyboard.Type='System.Windows.Media.Animation.Storyboard'; StoryboardName='CheckedStoryboard'; TargetElement='System.Windows.Controls.Grid'; TargetElement.HashCode='41837403'; TargetElement.Type='System.Windows.Controls.Grid'; NameScope='<null>'
System.Windows.Media.Animation Stop: 1 : 
System.Windows.Media.Animation Start: 3 : Storyboard has been removed; Storyboard='System.Windows.Media.Animation.Storyboard'; Storyboard.HashCode='16977025'; Storyboard.Type='System.Windows.Media.Animation.Storyboard'; StoryboardName='CheckedStoryboard'; TargetElement='System.Windows.Controls.Grid'; TargetElement.HashCode='41837403'; TargetElement.Type='System.Windows.Controls.Grid'
System.Windows.Media.Animation Stop: 3 : 
System.Windows.Media.Animation Start: 1 : Storyboard has begun; Storyboard='System.Windows.Media.Animation.Storyboard'; Storyboard.HashCode='16977025'; Storyboard.Type='System.Windows.Media.Animation.Storyboard'; StoryboardName='CheckedStoryboard'; TargetElement='System.Windows.Controls.Grid'; TargetElement.HashCode='41837403'; TargetElement.Type='System.Windows.Controls.Grid'; NameScope='<null>'
System.Windows.Media.Animation Stop: 1 : 

转换未能成功完成时,我得到以下输出:

System.Windows.Media.Animation Start: 1 : Storyboard has begun; Storyboard='System.Windows.Media.Animation.Storyboard'; Storyboard.HashCode='44177654'; Storyboard.Type='System.Windows.Media.Animation.Storyboard'; StoryboardName='UncheckedStoryboard'; TargetElement='System.Windows.Controls.Grid'; TargetElement.HashCode='41837403'; TargetElement.Type='System.Windows.Controls.Grid'; NameScope='<null>'
System.Windows.Media.Animation Stop: 1 : 
System.Windows.Media.Animation Start: 1 : Storyboard has begun; Storyboard='System.Windows.Media.Animation.Storyboard'; Storyboard.HashCode='6148812'; Storyboard.Type='System.Windows.Media.Animation.Storyboard'; StoryboardName='UncheckedStoryboard'; TargetElement='System.Windows.Controls.Grid'; TargetElement.HashCode='8261103'; TargetElement.Type='System.Windows.Controls.Grid'; NameScope='<null>'
System.Windows.Media.Animation Stop: 1 : 
System.Windows.Media.Animation Start: 1 : Storyboard has begun; Storyboard='System.Windows.Media.Animation.Storyboard'; Storyboard.HashCode='36205315'; Storyboard.Type='System.Windows.Media.Animation.Storyboard'; StoryboardName='UncheckedStoryboard'; TargetElement='System.Windows.Controls.Grid'; TargetElement.HashCode='18626439'; TargetElement.Type='System.Windows.Controls.Grid'; NameScope='<null>'
System.Windows.Media.Animation Stop: 1 : 
System.Windows.Media.Animation Start: 3 : Storyboard has been removed; Storyboard='System.Windows.Media.Animation.Storyboard'; Storyboard.HashCode='44177654'; Storyboard.Type='System.Windows.Media.Animation.Storyboard'; StoryboardName='UncheckedStoryboard'; TargetElement='System.Windows.Controls.Grid'; TargetElement.HashCode='41837403'; TargetElement.Type='System.Windows.Controls.Grid'
System.Windows.Media.Animation Stop: 3 : 
System.Windows.Media.Animation Start: 1 : Storyboard has begun; Storyboard='System.Windows.Media.Animation.Storyboard'; Storyboard.HashCode='36893403'; Storyboard.Type='System.Windows.Media.Animation.Storyboard'; StoryboardName='CheckingStoryboard'; TargetElement='System.Windows.Controls.Grid'; TargetElement.HashCode='41837403'; TargetElement.Type='System.Windows.Controls.Grid'; NameScope='<null>'
System.Windows.Media.Animation Stop: 1 : 
System.Windows.Media.Animation Start: 1 : Storyboard has begun; Storyboard='System.Windows.Media.Animation.Storyboard'; Storyboard.HashCode='49590434'; Storyboard.Type='System.Windows.Media.Animation.Storyboard'; StoryboardName='<null>'; TargetElement='System.Windows.Controls.Grid'; TargetElement.HashCode='41837403'; TargetElement.Type='System.Windows.Controls.Grid'; NameScope='<null>'
System.Windows.Media.Animation Stop: 1 : 

前12行与转换成功时完全相同,但最后10行完全缺失!

我已经阅读了所有可以找到的VSM文档,并且无法对这种不稳定的行为提出解释.

我是否认为这是VSM中的错误？这个问题有任何已知的解释或解决方法吗？

Answer 1

我已经能够识别并解决问题如下:

首先,我将我的repro项目降级为.NET 3.5并从CodePlex获取了WPF Toolkit源代码.我将WPF Toolkit项目添加到我的解决方案中,并从Repro项目中添加了对它的引用.

接下来,我运行了应用程序,并确保我仍然可以重现该问题.果然,很容易做到这一点.

然后我破解了VisualStateManager.cs文件,并开始在关键位置添加一些诊断程序,告诉我正在运行什么代码和什么不运行.通过添加这些诊断并比较良好转换到错误转换的输出,我很快就能够确定在问题出现时以下代码没有运行:

// Hook up generated Storyboard's Completed event handler
dynamicTransition.Completed += delegate
{
    if (transition.Storyboard == null ||
        transition.ExplicitStoryboardCompleted)
    {
        if (ShouldRunStateStoryboard(control, element, state, group))
        {
            group.StartNewThenStopOld(element, state.Storyboard);
        }

        group.RaiseCurrentStateChanged(element, lastState, state,
                                        control);
    }

    transition.DynamicStoryboardCompleted = true;
};

因此,错误的本质从VSM中的问题转移到Storyboard.Completed事件中的问题并不总是被提出.这是我之前遇到过的一个问题,对于任何WPF开发人员来说,在动画方面做任何与众不同的事情似乎都会引起很多焦虑.

在整个过程中,我将我的发现发布在WPF Disciples谷歌小组中,正是在这一点上,Pavan Podila回应了这个宝石:

肯特,

我过去曾经遇到过没有解雇完成事件的故事板的问题.我已经意识到,如果您直接替换故事板,而不先停止它,您可能会看到一些无序的已完成事件.在我的情况下,我将更新的故事板应用于同一个FrameworkElement,而没有停止早期的故事板,这给了我一些问题.不确定你的情况是否相似,但我想我会分享这个小贴士.

帕文

有了这种洞察力,我在VisualStateManager.cs中更改了这一行:

group.StartNewThenStopOld(element, transition.Storyboard, dynamicTransition); 

对此:

var masterStoryboard = new Storyboard();

if (transition.Storyboard != null)
{
    masterStoryboard.Children.Add(transition.Storyboard);
}

masterStoryboard.Children.Add(dynamicTransition);
group.StartNewThenStopOld(element, masterStoryboard);

并且 - 瞧瞧 - 我以前间歇性地失败的复制者现在每次都在工作!

所以,这真的解决了WPF动画子系统中的错误或奇怪的行为.