UWP动画问题，第一次动画正常第二次开始就不正常了

悬赏园豆：50 [已解决问题] 解决于 2016-09-07 23:17

<!--#region 子框架进入动画-->
        <Storyboard x:Name="childrenInStoryboard"
                x:FieldModifier="public">
            <DoubleAnimationUsingKeyFrames x:Name="childrenInDA"
                             Storyboard.TargetName="RootGrid"
                             Storyboard.TargetProperty="(UIElement.RenderTransform).(CompositeTransform.TranslateX)">
                <EasingDoubleKeyFrame KeyTime="0" Value="0"/>
                <EasingDoubleKeyFrame KeyTime="0:0:0.5" Value="0">
                    <EasingDoubleKeyFrame.EasingFunction>
                        <QuarticEase  EasingMode="EaseIn"/>
                    </EasingDoubleKeyFrame.EasingFunction>
                </EasingDoubleKeyFrame>
            </DoubleAnimationUsingKeyFrames>
        </Storyboard>
        <!--#endregion-->
        <!--#region 子框架退出动画-->
        <Storyboard x:Name="childrenOutStoryboard"
                x:FieldModifier="public">
            <DoubleAnimationUsingKeyFrames x:Name="childrenOutDA"
                             Storyboard.TargetName="RootGrid"
                             Storyboard.TargetProperty="(UIElement.RenderTransform).(CompositeTransform.TranslateX)">
                <EasingDoubleKeyFrame KeyTime="0" Value="0"/>
                <EasingDoubleKeyFrame KeyTime="0:0:0.5" Value="0">
                    <EasingDoubleKeyFrame.EasingFunction>
                        <QuarticEase  EasingMode="EaseInOut"/>
                    </EasingDoubleKeyFrame.EasingFunction>
                </EasingDoubleKeyFrame>
            </DoubleAnimationUsingKeyFrames>
        </Storyboard>
        <!--#endregion-->

<Grid Background="{ThemeResource ApplicationPageBackgroundThemeBrush}"
          Name="RootGrid"
          Loaded="RootGrid_Loaded">
        <Grid.RenderTransform>
            <CompositeTransform/>
        </Grid.RenderTransform>
    </Grid>

这个是XAML；我使用手机的后退按钮来退出

这里的Frame是我在MainPage中定义的一个名字为childrenFrame的Frame，从mainpage的listboxItem跳转的。下面是后台代码：

public sealed partial class SafePage : Page
    {
        public SafePage()
        {
            this.InitializeComponent();
            SystemNavigationManager.GetForCurrentView().BackRequested += SafePage_BackRequested;
            childrenOutStoryboard.Completed += ChildrenOutStoryboard_Completed;
            
        }
        
        private void ChildrenOutStoryboard_Completed(object sender, object e)
        {
            
            tempE = false;
            Frame.Visibility = Visibility.Collapsed;
            Frame.BackStack.Clear();
            (RootGrid.RenderTransform as CompositeTransform).TranslateX = 0;
        }
        

        //声明一个Bool值
        bool tempE = true;
        /// <summary>
        /// 退出动画
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void SafePage_BackRequested(object sender, BackRequestedEventArgs e)
        {
            e.Handled = tempE;
            if (!Frame.CanGoBack)
            {
　　　　　　　　　//Tools.ScreenSize().Width是一个自定义方法用来获取手机屏幕的实际分辨率
                childrenOutDA.KeyFrames[1].Value = Tools.ScreenSize().Width;
                childrenOutStoryboard.Begin();
            }
            else
            {
                Frame.GoBack();
            }
        }

      
        /// <summary>
        /// 载入动画
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void RootGrid_Loaded(object sender, RoutedEventArgs e)
        {
　　　　　　　//Tools.ScreenSize().Width是一个自定义方法用来获取手机屏幕的实际分辨率
            childrenInDA.KeyFrames[0].Value = Tools.ScreenSize().Width;
            childrenInStoryboard.Begin();
        }
    }