使用长列表选择器Windows Phone 8进行拉式刷新

我目前正在使用Windows Phone 8应用程序，并且在长列表选择器（LLS）方面遇到了一些问题。列表框使用TranslateY值：

 UIElement scrollContent = (UIElement)this.targetScrollViewer.Content;
 CompositeTransform ct = scrollContent.RenderTransform as CompositeTransform;
 //ct.TranslateY: I need this value in Viewport's LLS to detect exactly the distance moving from the TOP

我试图用LLS检测pull以刷新，但它有一些缺陷（使用鼠标输入、MOve和Leave），如：

    double manipulationStart = 0;
    double manipulationEnd = 0;
    void targetLLS_MouseEnter(object sender, MouseEventArgs e)
    {
        if (!this.IsRefreshing)
        {
            var pos = e.GetPosition(null);
            manipulationStart = pos.Y;
            IsMoving = false;
        }
    }
    private void targetLLS_MouseMove(object sender, MouseEventArgs e)
    {
        if (!this.IsRefreshing)
        {
            var pos = e.GetPosition(null);
            manipulationEnd = pos.Y;
            IsMoving = true;
            double TranslateY = manipulationEnd - manipulationStart;
            if (TranslateY > this.PullThreshold)
            {
                this.PullDistance = 100;
                this.PullFraction = 1.0;
                activityState = PullDownToRefreshPanel.ReadyToReleaseVisualState;
            }
            else if (TranslateY > 0)
            {
                this.PullDistance = 100;
                double threshold = this.PullThreshold;
                this.PullFraction = 1;// threshold == 0.0 ? 1.0 : Math.Min(1.0, TranslateY / threshold);
                activityState = PullDownToRefreshPanel.PullingDownVisualState;
            }
            else
            {
                this.PullDistance = 0;
                this.PullFraction = 0;
                activityState = PullDownToRefreshPanel.InactiveVisualState;
            }
            VisualStateManager.GoToState(this, activityState, false);
        }
    }
    bool IsMoving = false;
    void targetLLS_MouseLeave(object sender, MouseEventArgs e)
    {
        if (!this.IsRefreshing && IsMoving)
        {
            double TranslateY = manipulationEnd - manipulationStart;
            EventHandler handler = this.RefreshRequested;
            if (this.targetLLS.IsAtTop()
                && (activityState == PullDownToRefreshPanel.ReadyToReleaseVisualState))// TranslateY >= this.PullThreshold
            {
                if (handler != null)
                {
                    IsRefreshing = true;
                    handler(this, EventArgs.Empty);
                }
            }
            IsMoving = false;
        }
        PullDistance = 0;
        PullFraction = 0;
        manipulationStart = 0;
        manipulationEnd = 0;
        activityState = PullDownToRefreshPanel.InactiveVisualState;
        //VisualStateManager.GoToState(this, activityState, false);
    }

如何使用以下模板：

 <Style x:Key="ViewportControlStyle" TargetType="ViewportControl">
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="ViewportControl">
                <ContentPresenter x:Name="ContentElement" Cursor="{TemplateBinding Cursor}" ContentTemplate="{TemplateBinding ContentTemplate}" Content="{TemplateBinding Content}" HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" Margin="{TemplateBinding Padding}" VerticalAlignment="{TemplateBinding VerticalContentAlignment}"/>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style>
<Style x:Key="LongListSelectorNormalStyle" TargetType="phone:LongListSelector">
    <Setter Property="Background" Value="Transparent"/>
    <Setter Property="Foreground" Value="{StaticResource PhoneForegroundBrush}"/>
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="phone:LongListSelector">
                <Grid Background="{TemplateBinding Background}">
                    <VisualStateManager.VisualStateGroups>
                        <VisualStateGroup x:Name="ScrollStates">
                            <VisualStateGroup.Transitions>
                                <VisualTransition GeneratedDuration="00:00:00.5"/>
                            </VisualStateGroup.Transitions>
                            <VisualState x:Name="Scrolling">
                                <Storyboard>
                                    <DoubleAnimation Duration="0" To="1" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="VerticalScrollBar"/>
                                </Storyboard>
                            </VisualState>
                            <VisualState x:Name="NotScrolling"/>
                        </VisualStateGroup>
                    </VisualStateManager.VisualStateGroups>
                    <Grid Margin="{TemplateBinding Padding}">
                        <Grid.ColumnDefinitions>
                            <ColumnDefinition Width="*"/>
                        </Grid.ColumnDefinitions>
                        <ViewportControl x:Name="ViewportControl" HorizontalContentAlignment="Stretch" VerticalAlignment="Top" Style="{StaticResource ViewportControlStyle}"/>
                        <ScrollBar x:Name="VerticalScrollBar" Grid.Column="0" Margin="4,0,4,0" Opacity="0" Orientation="Vertical" HorizontalAlignment="Right"/>
                    </Grid>
                </Grid>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style>

我的项目需要实现pull功能，所以请帮助我。感谢阅读！