网格列在动画时改变宽度

我有一个具有两列和三行的网格元素。最后一行的高度为 0...并且我使用自定义动画类对 height 属性进行动画处理，因为 gridheight 属性不是整数。

动画工作得很好，但是当我激活它时，它似乎随机地改变了第二列的宽度..有时只是大几个像素，有时宽度超过两倍...

这是网格代码

<Grid >
                        <Grid.ColumnDefinitions>
                            <ColumnDefinition />
                            <ColumnDefinition Width="50"/>
                        </Grid.ColumnDefinitions>
                        <Grid.RowDefinitions>
                            <RowDefinition Height="1*" />
                            <RowDefinition Height="7"/>
                            <RowDefinition Name="LyricsRow" Height="1">

                                <RowDefinition.Style>
                                    <Style>
                                        <Style.Triggers>
                                            <DataTrigger Binding="{Binding Path=IsTrayOpen}" Value="True">
                                                <DataTrigger.EnterActions>
                                                    <BeginStoryboard>
                                                        <Storyboard>
                                                            <local:GridLengthAnimation
                                                              Storyboard.TargetProperty="Height"
                                                              From="0" To="150" Duration="0:0:0.3" >
                                                            </local:GridLengthAnimation>
                                                        </Storyboard>
                                                    </BeginStoryboard>
                                                </DataTrigger.EnterActions>
                                                <DataTrigger.ExitActions>
                                                    <BeginStoryboard>
                                                        <Storyboard>
                                                            <local:GridLengthAnimation
                                                              Storyboard.TargetProperty="Height"
                                                              From="150" To="0" Duration="0:0:0.5" />
                                                        </Storyboard>
                                                    </BeginStoryboard>
                                                </DataTrigger.ExitActions>
                                            </DataTrigger>
                                        </Style.Triggers>
                                    </Style>
                                </RowDefinition.Style>

                            </RowDefinition>
                        </Grid.RowDefinitions>

有什么原因可能会发生这种情况吗？

对于那些可能想知道问题中提到的 GridLengthAnimation 实现的人，这里有一个（来自http://social.msdn.microsoft.com/forums/en-US/wpf/thread/da47a4b8-4d39-4d6e-a570-7dbe51a842e4/)

/// <summary>
/// Animates a grid length value just like the DoubleAnimation animates a double value
/// </summary>
public class GridLengthAnimation : AnimationTimeline
{
    /// <summary>
    /// Returns the type of object to animate
    /// </summary>
    public override Type TargetPropertyType
    {
        get
        {
            return typeof(GridLength);
        }
    }

    /// <summary>
    /// Creates an instance of the animation object
    /// </summary>
    /// <returns>Returns the instance of the GridLengthAnimation</returns>
    protected override System.Windows.Freezable CreateInstanceCore()
    {
        return new GridLengthAnimation();
    }

    /// <summary>
    /// Dependency property for the From property
    /// </summary>
    public static readonly DependencyProperty FromProperty = DependencyProperty.Register("From", typeof(GridLength),
            typeof(GridLengthAnimation));

    /// <summary>
    /// CLR Wrapper for the From depenendency property
    /// </summary>
    public GridLength From
    {
        get
        {
            return (GridLength)GetValue(GridLengthAnimation.FromProperty);
        }
        set
        {
            SetValue(GridLengthAnimation.FromProperty, value);
        }
    }

    /// <summary>
    /// Dependency property for the To property
    /// </summary>
    public static readonly DependencyProperty ToProperty = DependencyProperty.Register("To", typeof(GridLength),
            typeof(GridLengthAnimation));

    /// <summary>
    /// CLR Wrapper for the To property
    /// </summary>
    public GridLength To
    {
        get
        {
            return (GridLength)GetValue(GridLengthAnimation.ToProperty);
        }
        set
        {
            SetValue(GridLengthAnimation.ToProperty, value);
        }
    }

    /// <summary>
    /// Animates the grid let set
    /// </summary>
    /// <param name="defaultOriginValue">The original value to animate</param>
    /// <param name="defaultDestinationValue">The final value</param>
    /// <param name="animationClock">The animation clock (timer)</param>
    /// <returns>Returns the new grid length to set</returns>
    public override object GetCurrentValue(object defaultOriginValue,
        object defaultDestinationValue, AnimationClock animationClock)
    {
        double fromVal = ((GridLength)GetValue(GridLengthAnimation.FromProperty)).Value;
        //check that from was set from the caller
        if (fromVal == 1)
            //set the from as the actual value
            fromVal = ((GridLength)defaultDestinationValue).Value;

        double toVal = ((GridLength)GetValue(GridLengthAnimation.ToProperty)).Value;

        if (fromVal > toVal)
            return new GridLength((1 - animationClock.CurrentProgress.Value) * (fromVal - toVal) + toVal, GridUnitType.Star);
        else
            return new GridLength(animationClock.CurrentProgress.Value * (toVal - fromVal) + fromVal, GridUnitType.Star);
    }
}