《ListBox》———何如实现ListBox下拉刷新和到底部自动加载

一、下拉刷新
下拉刷新实现思路：
1、定义一个PullDownToRefreshPanel容器控件。为它添加3种状态模板，分别是PullingDownTemplate，ReadyToReleaseTemplate
     和RefreshingTemplate，顾名思义分别是显示下拉状态模板，显示松开刷新状态模板和正在刷新中的状态模板。
2、定义自己的ListBox让它继承系统的ListBox，并重写它的Style，把ScrollViewer的ManipulationMode属性设为Conrtrol（必需），
     只有这样才能和我们的定义的PullDownToRefreshPanel兼容。ManipulationMode属性系统默认是System；区别就是，System的
     滑动效果更好。这里的ListBox的Style定义可以参考安装的SDK目录里面的系统定义，路径大致是：c->Program Files(x86)->
     Microsoft SDKs->Windows Phone->v7.1->Design->System.Windows.xaml.

<Style TargetType="rlb:CustListBox">

<Setter Property="Background" Value="Transparent" />

<Setter Property="Foreground" Value="{StaticResource PhoneForegroundBrush}" />

<Setter Property="ScrollViewer.HorizontalScrollBarVisibility" Value="Disabled" />

<Setter Property="ScrollViewer.VerticalScrollBarVisibility" Value="Auto" />

<Setter Property="BorderThickness" Value="0" />

<Setter Property="BorderBrush" Value="Transparent" />

<Setter Property="Padding" Value="0" />

<Setter Property="Template">

<Setter.Value>

<ControlTemplate TargetType="rlb:CustListBox">

<Grid>

<Grid.ColumnDefinitions>

<ColumnDefinition Width="*" />

<ColumnDefinition Width="Auto" />

</Grid.ColumnDefinitions>

<!-- ScrollViewer的ManipulationMode属性必须设为Conrtrol才能和PullDownToRefreshPanel兼容 -->

<!-- ScrollViewer的ManipulationMode属性默认是System它能提供更好的滚动效果 -->

<ScrollViewer x:Name="ScrollViewer" Grid.ColumnSpan="2" ManipulationMode="Control" Foreground="{TemplateBinding Foreground}" Background="{TemplateBinding Background}"

BorderBrush="Transparent" BorderThickness="0" Padding="{TemplateBinding Padding}">

<ItemsPresenter />

</ScrollViewer>

<!-- The DragInterceptor sits on top of the item DragHandles and intercepts drag events

so that the capture is not lost when the item container is removed from the panel.

Its width must be equal to the width of the item DragHandles. -->

<Canvas x:Name="DragInterceptor" Grid.Column="1" Margin="{TemplateBinding Padding}" Background="Transparent" VerticalAlignment="Stretch" Width="52">

<Image x:Name="DragIndicator" Visibility="Collapsed">

<Image.RenderTransform>

<TranslateTransform />

</Image.RenderTransform>

</Image>

</Canvas>

<Canvas x:Name="RearrangeCanvas" Grid.ColumnSpan="2" Margin="{TemplateBinding Padding}" Background="Transparent" Visibility="Collapsed" />

</Grid>

</ControlTemplate>

</Setter.Value>

</Setter>

</Style>



<Style TargetType="rlb:PullDownToRefreshPanel">

<Setter Property="Background" Value="Transparent" />

<Setter Property="PullingDownTemplate">

<Setter.Value>

<DataTemplate>

<TextBlock Margin="0,16,0,0" Style="{StaticResource PhoneTextGroupHeaderStyle}" TextAlignment="Center" FontStyle="Italic" Text="Pull down to refresh." />

</DataTemplate>

</Setter.Value>

</Setter>

<Setter Property="ReadyToReleaseTemplate">

<Setter.Value>

<DataTemplate>

<TextBlock Margin="0,16,0,0" Style="{StaticResource PhoneTextGroupHeaderStyle}" TextAlignment="Center" FontWeight="Bold" Text="Release to refresh!" />

</DataTemplate>

</Setter.Value>

</Setter>

<Setter Property="RefreshingTemplate">

<Setter.Value>

<DataTemplate>

<ProgressBar Margin="0,4,0,4" IsIndeterminate="True" />

</DataTemplate>

</Setter.Value>

</Setter>

<Setter Property="Template">

<Setter.Value>

<ControlTemplate TargetType="rlb:PullDownToRefreshPanel">

<StackPanel x:Name="PullDownContainer" HorizontalAlignment="Stretch">

<StackPanel.Resources>

<rlb:NegativeValueConverter x:Key="NegativeValueConverter" />

</StackPanel.Resources>

<StackPanel x:Name="PullingDownPanel" Background="{TemplateBinding Background}" Height="{TemplateBinding PullDistance}" Opacity="{TemplateBinding PullFraction}"

Margin="{Binding PullDistance, RelativeSource={RelativeSource TemplatedParent}, Converter={StaticResource NegativeValueConverter}, ConverterParameter=Bottom}" Visibility="Collapsed">

<ContentPresenter ContentTemplate="{TemplateBinding PullingDownTemplate}" />

</StackPanel>

<StackPanel x:Name="ReadyToReleasePanel" Background="{TemplateBinding Background}" Height="{TemplateBinding PullDistance}"

Margin="{Binding PullDistance, RelativeSource={RelativeSource TemplatedParent}, Converter={StaticResource NegativeValueConverter}, ConverterParameter=Bottom}" Visibility="Collapsed">

<ContentPresenter ContentTemplate="{TemplateBinding ReadyToReleaseTemplate}" />

</StackPanel>

<StackPanel x:Name="RefreshingPanel" Background="{TemplateBinding Background}" Visibility="Collapsed">

<ContentPresenter ContentTemplate="{TemplateBinding RefreshingTemplate}" />

</StackPanel>

<VisualStateManager.VisualStateGroups>

<VisualStateGroup x:Name="ActivityStates">

<VisualState x:Name="Inactive" />

<VisualState x:Name="PullingDown">

<Storyboard>

<ObjectAnimationUsingKeyFrames Storyboard.TargetName="PullingDownPanel" Storyboard.TargetProperty="Visibility">

<DiscreteObjectKeyFrame KeyTime="0" Value="Visible" />

</ObjectAnimationUsingKeyFrames>

</Storyboard>

</VisualState>

<VisualState x:Name="ReadyToRelease">

<Storyboard>

<ObjectAnimationUsingKeyFrames Storyboard.TargetName="ReadyToReleasePanel" Storyboard.TargetProperty="Visibility">

<DiscreteObjectKeyFrame KeyTime="0" Value="Visible" />

</ObjectAnimationUsingKeyFrames>

</Storyboard>

</VisualState>

<VisualState x:Name="Refreshing">

<Storyboard>

<ObjectAnimationUsingKeyFrames Storyboard.TargetName="RefreshingPanel" Storyboard.TargetProperty="Visibility">

<DiscreteObjectKeyFrame KeyTime="0" Value="Visible" />

</ObjectAnimationUsingKeyFrames>

</Storyboard>

</VisualState>

</VisualStateGroup>

</VisualStateManager.VisualStateGroups>

</StackPanel>

</ControlTemplate>

</Setter.Value>

</Setter>

</Style>

3、编写PullDownToRefreshPanel控件，主要是把PullDownToRefreshPanel和ScrollViewer联系起来，通过PullDwonReflesh距离滚动条的位置
     来实现下拉刷新功能. 具体的实现，代码里有很好的注释。相信难不到你

/// <summary>

/// 给滚得条添加下拉刷新机制

/// </summary>

/// <remarks>

/// 使用PullDwonReflesh距离滚动条的位置来实现下拉刷新功能. 

/// 包含PullDwonReflesh的容器，必须直接或间接的包含滚动条。

/// 例如：一个StackPanel包含一个PullDownToRefreshPanel 和一个ListBox，

/// 而ListBox内部包含一个ScrollViewer来实现子项的显示。

/// </remarks>

[TemplateVisualState(Name = PullDownToRefreshPanel.InactiveVisualState, GroupName = PullDownToRefreshPanel.ActivityVisualStateGroup)]

[TemplateVisualState(Name = PullDownToRefreshPanel.PullingDownVisualState, GroupName = PullDownToRefreshPanel.ActivityVisualStateGroup)]

[TemplateVisualState(Name = PullDownToRefreshPanel.ReadyToReleaseVisualState, GroupName = PullDownToRefreshPanel.ActivityVisualStateGroup)]

[TemplateVisualState(Name = PullDownToRefreshPanel.RefreshingVisualState, GroupName = PullDownToRefreshPanel.ActivityVisualStateGroup)]

public class PullDownToRefreshPanel : Control

{

#region Visual state name constants

//滚动中

private const string ActivityVisualStateGroup = "ActivityStates";

//无操作

private const string InactiveVisualState = "Inactive";

//下拉

private const string PullingDownVisualState = "PullingDown";

//松手刷新

private const string ReadyToReleaseVisualState = "ReadyToRelease";

//刷新中

private const string RefreshingVisualState = "Refreshing";



#endregion



/// <summary>

/// 用于绑定下拉文字显示，松手刷新的滚动条

/// </summary>

private ScrollViewer targetScrollViewer;



/// <summary>

/// 构造函数

/// </summary>

public PullDownToRefreshPanel()

{

this.DefaultStyleKey = typeof(PullDownToRefreshPanel);

this.LayoutUpdated += this.PullDownToRefreshPanel_LayoutUpdated;

}



/// <summary>

/// 当滚动条下拉到指定程度(PullThreshold)时引发这个事件，并显示松手刷新

/// 如果开始刷新的时候事件要把IsRefreshing设置为true

/// 当刷新完成时把IsRefreshing设回false.

/// </summary>

public event EventHandler RefreshRequested;



#region IsRefreshing DependencyProperty 是否正在刷新



public static readonly DependencyProperty IsRefreshingProperty = DependencyProperty.Register

(

"IsRefreshing", typeof(bool), typeof(PullDownToRefreshPanel),

new PropertyMetadata(false, (d, e) => 

{

((PullDownToRefreshPanel)d).OnIsRefreshingChanged(e); 

})

);



public bool IsRefreshing

{

get

{

return (bool)this.GetValue(PullDownToRefreshPanel.IsRefreshingProperty);

}

set

{

this.SetValue(PullDownToRefreshPanel.IsRefreshingProperty, value);

}

}



protected void OnIsRefreshingChanged(DependencyPropertyChangedEventArgs e)

{

string activityState = (bool)e.NewValue ? PullDownToRefreshPanel.RefreshingVisualState : PullDownToRefreshPanel.InactiveVisualState;

VisualStateManager.GoToState(this, activityState, false);

}



#endregion



#region PullThreshold DependencyProperty 设置下拉距离



public static readonly DependencyProperty PullThresholdProperty = DependencyProperty.Register(

"PullThreshold", typeof(double), typeof(PullDownToRefreshPanel), new PropertyMetadata(100.0));



/// <summary>

/// 得到或设置一个滚动条从顶部下拉的最小距离，当达到这个距离松手时会触发刷新事件

/// 默认距离是100. 推荐最大值不要超过125.

/// </summary>

public double PullThreshold

{

get

{

return (double)this.GetValue(PullDownToRefreshPanel.PullThresholdProperty);

}

set

{

this.SetValue(PullDownToRefreshPanel.PullThresholdProperty, value);

}

}



#endregion



#region PullDistance DependencyProperty 滚动条拉下的距离



public static readonly DependencyProperty PullDistanceProperty = DependencyProperty.Register(

"PullDistance", typeof(double), typeof(PullDownToRefreshPanel), new PropertyMetadata(0.0));



/// <summary>

/// 得到滚动条已经拉下的距离。

/// 用它绑定图形距离

/// </summary>

public double PullDistance

{

get

{

return (double)this.GetValue(PullDownToRefreshPanel.PullDistanceProperty);

}

private set

{

this.SetValue(PullDownToRefreshPanel.PullDistanceProperty, value);

}

}



#endregion 



#region PullFraction DependencyProperty 相对PullDistance拉下距离分值



public static readonly DependencyProperty PullFractionProperty = DependencyProperty.Register(

"PullFraction", typeof(double), typeof(PullDownToRefreshPanel), new PropertyMetadata(0.0));



/// <summary>

/// 得到滚动条从顶部拉下的距离分数。即拉下PullThreshold的几分之几，取值范围（0.0 - 1.0）

/// </summary>

public double PullFraction

{

get

{

return (double)this.GetValue(PullDownToRefreshPanel.PullFractionProperty);

}

private set

{

this.SetValue(PullDownToRefreshPanel.PullFractionProperty, value);

}

}



#endregion



#region PullingDownTemplate DependencyProperty 提示下拉刷新的模板



public static readonly DependencyProperty PullingDownTemplateProperty = DependencyProperty.Register(

"PullingDownTemplate", typeof(DataTemplate), typeof(PullDownToRefreshPanel), null);



/// <summary>

/// Gets or sets a template that is progressively revealed has the ScrollViewer is pulled down.

/// </summary>

public DataTemplate PullingDownTemplate

{

get

{

return (DataTemplate)this.GetValue(PullDownToRefreshPanel.PullingDownTemplateProperty);

}

set

{

this.SetValue(PullDownToRefreshPanel.PullingDownTemplateProperty, value);

}

}



#endregion



#region ReadyToReleaseTemplate DependencyProperty 提示松开刷新的模板



public static readonly DependencyProperty ReadyToReleaseTemplateProperty = DependencyProperty.Register(

"ReadyToReleaseTemplate", typeof(DataTemplate), typeof(PullDownToRefreshPanel), null);



/// <summary>

/// Gets or sets the template that is displayed after the ScrollViewer is pulled down past

/// the PullThreshold.

/// </summary>

public DataTemplate ReadyToReleaseTemplate

{

get

{

return (DataTemplate)this.GetValue(PullDownToRefreshPanel.ReadyToReleaseTemplateProperty);

}

set

{

this.SetValue(PullDownToRefreshPanel.ReadyToReleaseTemplateProperty, value);

}

}



#endregion



#region RefreshingTemplate DependencyProperty 提示正在刷新的模板



public static readonly DependencyProperty RefreshingTemplateProperty = DependencyProperty.Register(

"RefreshingTemplate", typeof(DataTemplate), typeof(PullDownToRefreshPanel), null);



/// <summary>

/// Gets or sets the template that is displayed while the ScrollViewer is refreshing.

/// </summary>

public DataTemplate RefreshingTemplate

{

get

{

return (DataTemplate)this.GetValue(PullDownToRefreshPanel.RefreshingTemplateProperty);

}

set

{

this.SetValue(PullDownToRefreshPanel.RefreshingTemplateProperty, value);

}

}



#endregion



#region Initial setup 初始化设置



private void PullDownToRefreshPanel_LayoutUpdated(object sender, EventArgs e)

{

if (this.targetScrollViewer == null)

{

//找到要绑定的目标滚动条

this.targetScrollViewer = FindVisualElement<ScrollViewer>(VisualTreeHelper.GetParent(this));

App._ScrollViewer = targetScrollViewer;

if (this.targetScrollViewer != null)

{

this.targetScrollViewer.MouseMove += this.targetScrollViewer_MouseMove;

this.targetScrollViewer.MouseLeftButtonUp += this.targetScrollViewer_MouseLeftButtonUp;



//滚得条的类型必须是控件类型

if (this.targetScrollViewer.ManipulationMode != ManipulationMode.Control)

{

throw new InvalidOperationException("PullDownToRefreshPanel requires the ScrollViewer " +

"to have ManipulationMode=Control. (ListBoxes may require re-templating.");

}

}

}

}



#endregion



#region Pull-down detection 下拉检测



/// <summary>

/// 当滚动条被拖拽时，显示动画和对应的控件模型

/// </summary>

private void targetScrollViewer_MouseMove(object sender, MouseEventArgs e)

{

UIElement scrollContent = (UIElement)this.targetScrollViewer.Content;

CompositeTransform ct = scrollContent.RenderTransform as CompositeTransform;

if (ct != null && !this.IsRefreshing)

{

string activityState;

if (ct.TranslateY > this.PullThreshold)

{

this.PullDistance = ct.TranslateY;

this.PullFraction = 1.0;

activityState = PullDownToRefreshPanel.ReadyToReleaseVisualState;

}

else if (ct.TranslateY > 0)

{

this.PullDistance = ct.TranslateY;

double threshold = this.PullThreshold;

this.PullFraction = threshold == 0.0 ? 1.0 : Math.Min(1.0, ct.TranslateY / threshold);

activityState = PullDownToRefreshPanel.PullingDownVisualState;

}

else

{

this.PullDistance = 0;

this.PullFraction = 0;

activityState = PullDownToRefreshPanel.InactiveVisualState;

}

VisualStateManager.GoToState(this, activityState, false);

}

}



/// <summary>

/// 当松手时检查是否要刷新

/// </summary>

private void targetScrollViewer_MouseLeftButtonUp(object sender, MouseButtonEventArgs e)

{

UIElement scrollContent = (UIElement)this.targetScrollViewer.Content;

CompositeTransform ct = scrollContent.RenderTransform as CompositeTransform;

if (ct != null && !this.IsRefreshing)

{

VisualStateManager.GoToState(this, PullDownToRefreshPanel.InactiveVisualState, false);

this.PullDistance = 0;

this.PullFraction = 0;



if (ct.TranslateY >= this.PullThreshold)

{

EventHandler handler = this.RefreshRequested;

if (handler != null)

{

handler(this, EventArgs.Empty);

}

}

}

}



#endregion



#region Utility methods 查找第一个符合要求的元素方法



/// <summary>

/// 查找容器内所有元素，并返回第一个是T类型的元素

/// </summary>

/// <typeparam name="T">要搜索的元素类型</typeparam>

/// <param name="initial">要搜索的容器</param>

/// <returns>返回要找的元素，没找到返回null</returns>

private static T FindVisualElement<T>(DependencyObject container) where T : DependencyObject

{

Queue<DependencyObject> childQueue = new Queue<DependencyObject>();

childQueue.Enqueue(container);



while (childQueue.Count > 0)

{

DependencyObject current = childQueue.Dequeue();



System.Diagnostics.Debug.WriteLine(current.GetType().ToString());



T result = current as T;

if (result != null && result != container)

{

return result;

}



int childCount = VisualTreeHelper.GetChildrenCount(current);

for (int childIndex = 0; childIndex < childCount; childIndex++)

{

childQueue.Enqueue(VisualTreeHelper.GetChild(current, childIndex));

}

}



return null;

}



#endregion

}

4、实现自定义ListBox->CustListBox，代码很简单直接上。

[TemplatePart(Name = CustListBox.ScrollViewerPart, Type = typeof(ScrollViewer))]

public class CustListBox : ListBox

{

public const string ScrollViewerPart = "ScrollViewer";



public CustListBox()

{

this.DefaultStyleKey = typeof(CustListBox);

}



#region AutoScrollMargin DependencyProperty



public static readonly DependencyProperty AutoScrollMarginProperty = DependencyProperty.Register(

"AutoScrollMargin", typeof(int), typeof(CustListBox), new PropertyMetadata(32));



public double AutoScrollMargin

{

get

{

return (int)this.GetValue(CustListBox.AutoScrollMarginProperty);

}

set

{

this.SetValue(CustListBox.AutoScrollMarginProperty, value);

}

}



#endregion

}

5、使用要求   
     包含PullDwonReflesh的容器，必须直接或间接的包含滚动条。
     例如：一个StackPanel包含一个PullDownToRefreshPanel 和一个ListBox，而ListBox内部包含一个ScrollViewer来实现子项的显示。
6、为了使用起来更方便，我把CustListBox和PullDownToRefreshPanel 又封装了一层
     xaml

<UserControl x:Class="PullDwonReflesh.Themes.CustListbox"

xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"

xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"

xmlns:d="http://schemas.microsoft.com/expression/blend/2008"

xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"

mc:Ignorable="d"

FontFamily="{StaticResource PhoneFontFamilyNormal}"

FontSize="{StaticResource PhoneFontSizeNormal}"

Foreground="{StaticResource PhoneForegroundBrush}"

d:DesignHeight="480" d:DesignWidth="480" xmlns:my="clr-namespace:PullDwonReflesh"



xmlns:toolkit="clr-namespace:Microsoft.Phone.Controls;assembly=Microsoft.Phone.Controls.Toolkit"

x:Name="this">



<Grid x:Name="LayoutRoot">

<Grid.RowDefinitions>

<RowDefinition Height="Auto" />

<RowDefinition Height="*" />

</Grid.RowDefinitions>

<my:PullDownToRefreshPanel x:Name="refreshPanel" RefreshRequested="refreshPanel_RefreshRequested" Grid.Row="0" />

<my:CustListBox x:Name="custListBox" Grid.Row="1" Margin="12,0,12,12" toolkit:TiltEffect.IsTiltEnabled="True"

ItemsSource="{Binding ElementName=this, Path=ItemsSource}" 

ItemTemplate="{Binding ElementName=this,Path=ItemTemplate}"

SelectionChanged="CustListBox_SelectionChanged" >

<!--<ListBox.ItemsPanel>

<ItemsPanelTemplate>

<toolkit:WrapPanel/>

</ItemsPanelTemplate>

</ListBox.ItemsPanel>

<ListBox.ItemContainerStyle>

<Style TargetType="ListBoxItem">

<Setter Property="HorizontalContentAlignment" Value="Stretch"/>

</Style>

</ListBox.ItemContainerStyle>-->

</my:CustListBox>

</Grid>

</UserControl>

using System;

using System.Collections.Generic;

using System.Linq;

using System.Net;

using System.Windows;

using System.Windows.Controls;

using System.Windows.Documents;

using System.Windows.Input;

using System.Windows.Media;

using System.Windows.Media.Animation;

using System.Windows.Shapes;

using System.Collections;



namespace PullDwonReflesh.Themes

{

public partial class CustListbox : UserControl

{

public event SelectionChangedEventHandler SelectionChanged;

public event EventHandler RefreshRequested;



public static readonly DependencyProperty ItemsSourceProperty = DependencyProperty.Register("ItemsSource", typeof(IEnumerable), typeof(CustListbox), new PropertyMetadata(""));

public IEnumerable ItemsSource

{

get

{

return (IEnumerable)base.GetValue(ItemsSourceProperty);

}

set

{

base.SetValue(ItemsSourceProperty, value);

}

}



private DataTemplate _ItemTemplate = null;

public DataTemplate ItemTemplate

{

get

{

return _ItemTemplate;

}

set

{

_ItemTemplate = value;

custListBox.ItemTemplate = value;

}

}



public static readonly DependencyProperty IsRefreshingProperty = DependencyProperty.Register("IsRefreshing", typeof(bool), typeof(CustListbox), new PropertyMetadata(false, (d, e) => ((CustListbox)d).OnIsRefreshingChanged(e)));

public bool IsRefreshing

{

get

{

return (bool)this.GetValue(CustListbox.IsRefreshingProperty);

}

set

{

this.SetValue(CustListbox.IsRefreshingProperty, value);

}

}



protected void OnIsRefreshingChanged(DependencyPropertyChangedEventArgs e)

{

this.refreshPanel.IsRefreshing = (bool)e.NewValue;

}



public CustListbox()

{

InitializeComponent();

}



private void CustListBox_SelectionChanged(object sender, SelectionChangedEventArgs e)

{

if (SelectionChanged != null)

{

SelectionChanged(sender, e);

}

}



private void refreshPanel_RefreshRequested(object sender, EventArgs e)

{

if (RefreshRequested != null)

{

RefreshRequested(sender, e);

}

}

}

}

到此，下拉刷新已经完成，可以拿出来单独使用。


二、ListBox滚动到底部自动加载
这个实现起来就更简单，思路
1、检测ListBox中的ScrollViewer控件状态
2、若状态不为滚动中：根据ScrollViewer的ExtentHeight与VerticalOffset，判断是否到底,并执行请求加载数据。

首先获取ScrollViewer，这个上面实现下拉的中已经得到了，这里在App定义一个变量把下拉时获得的ScrollViewer保存起来，并在这里作为目标滚动条。
然后编写获得状态函数，如下

private VisualStateGroup FindVisualState(FrameworkElement element, string name)

{

if (element == null)

return null;



IList groups = VisualStateManager.GetVisualStateGroups(element);

foreach (VisualStateGroup group in groups)

{

if (group.Name == name)

return group;

}



return null;

}

接下来根据状态的改变做相应的加载功能，代码如下

void visualStateGroup_CurrentStateChanged(object sender, VisualStateChangedEventArgs e)

{

var visualState = e.NewState.Name;

if (visualState == "NotScrolling")

{

var v1 = _ScrollViewer.ExtentHeight - _ScrollViewer.VerticalOffset;

var v2 = _ScrollViewer.ViewportHeight * 1.5;



if (v1 <= v2 && !custListBox.IsRefreshing)

{

AddString(index, 20);

visualState += "_End";

}

}

}

最后，在页面的loaded里把这些代码串联起来就OK了。如下：

private void PhoneApplicationPage_Loaded(object sender, RoutedEventArgs e)

{

if (_IsHookedScrollEvent)

return;

_ScrollViewer = App._ScrollViewer;

if (_ScrollViewer != null)

{

_IsHookedScrollEvent = true;

FrameworkElement element = VisualTreeHelper.GetChild(_ScrollViewer, 0) as FrameworkElement;

if (element != null)

{

VisualStateGroup visualStateGroup = FindVisualState(element, "ScrollStates");

visualStateGroup.CurrentStateChanged += new EventHandler<VisualStateChangedEventArgs>(visualStateGroup_CurrentStateChanged);

}

}

}

本文参考：http://www.hugwp.com/thread-2058-1.html
和Jason Ginchereau的博客

源码：猛击下载

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