WPF【无限滚动图片浏览】自定义控件

自定义控件

自定义控件是我比较陌生的一个主题。我好久没练习过wpf了，需要巩固记忆。我想了一会儿，打开动漫之家，忽然觉得这个看漫画的图片浏览控件有意思。于是特地花了一天做了这个图片控件。我原本以为很容易，但实际上并不简单。这个图片浏览控件比我想象中要难许多，有技术上的难题，也有逻辑上的难题。好在最后都解决了。

这个自定义控件算是比较好的练习。里面涉及了依赖属性 Binding 虚拟化加载 VisualState 动态资源 过渡效果 部件 光标这些东西。

光标制作

对于电脑端来说，一个好看的光标是必不可少的。于是我查询了资料，了解到一种比较简洁的自定义光标方式。就是制作光标文件，然后在XAML中直接使用。

<Button x:Name="P_Bleft" Opacity="0" Grid.Column="0" Cursor="/程序集;component/路径/left.cur">上一页</Button> <Button x:Name="P_Bright" Opacity="0" Grid.Column="1" Cursor="/程序集;component/路径/right.cur">下一页</Button> 

到哪里找图标呢呢？我想起了FontAwsome.V5，这个非常方便，并且美观。于是我到官网上找到了两个箭头图标。下一步是把图标转化成光标文件。FontAwsome.V5提供了svg格式的图标复制，然后我在这个网站发现了-->在线转换器<--可以将svg转化为cur光标文件，它提供了每天10次的免费额度。但要注意，需要设定光标尺寸。可以设置另存为文件之后，把svg元素的Width和Height属性改为16。

<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 512 512" width="16" height="16"> 

最后把光标文件放到项目中，以生成资源的形式编译。这里就能在XAML中直接使用了。如前面所示，是一个黑色箭头。

控制面板

作为一个图片浏览控件，控制面板必不可少。比较经典的做法是点击中间显示面板帮助。点击两边切换图片。面板帮助我就暂且省略，就做了切换图片的功能。整个自定义控件的是一个Grid，分为2列，然后两个按钮各占1列，再把按钮隐藏起来。幸好，透明度为0时还能捕获事件。下方再重叠几个宽度为2列的Image控件作为视口。

控件结构

经过多次更改，最终我把这个自定义控件设计为了一个分为4层Z-Index的控件。

• Z-Index=4 上一页、下一页
• Z-Index=3 当前页
• Z-Index=2 根据滑动方向确定的下一页
• Z-Index=1 上一页和下一页Z-Index之间的分隔板
• Z-Index=0 根据滑动方向确定的上一页
• 底层容器Grid

这是我为了实现正常显示效果，再调试过程中一层层加上去的。但是XAML中没法给非Canvas子控件设置这个附加属性，所以这个附加属性只能在逻辑控件的代码中进行动态设置。这些设置代码与控件交互逻辑交织，本身就是控制逻辑的一部分。

var P_Bleft = (Button)GetTemplateChild("P_Bleft"); P_Bleft.SetValue(Canvas.ZIndexProperty, 4); P_Bright.SetValue(Canvas.ZIndexProperty, 4); P_Bulkhead.SetValue(Canvas.ZIndexProperty, 1); 

虚拟化加载

作为一个图片浏览器，把全部图片一次性加载出来是一个方便的选择，但不是一个明智的选择。所以我考虑了虚拟化加载。最开始我想到了集合控件ListView。但是这个我需要过渡效果。集合控件似乎没有实现这个。并且对内容大小控制也不是很完美。我还是自己从0开始做。

我走了很多弯路，最后确定使用3个水平排列的Image控件进行图片的呈现。使用Storyboard时间线控制过渡效果。我把图片URL集合组织成一个环形，然后让这3个Image在环上移动，这样实现虚拟化加载。

首先是预加载当前页和下一页。点击下一页之后，图片控件向左移动，同时最左边的、移动到视口之外的Image控件加载下下一页。第二次点击时，把首次预加载的图片移动到视口内，再把第二次预加载的图片移动到下一页位置。第三次点击时，这个控件移动到视口内，每个控件都有类似的过程，循环往复。同时还要考虑方向，即点击上一页。所以这要在逻辑代码中判断处理。

我用简单的取模运算符将数据组织成环形

//当前页 int state = (Current) % 3; 

然后在一个switch结构中完成控制逻辑

switch (state) {     case 0: 	//很多判断 	break;     case 1: 	//很多判断 	break;     case 2: 	//很多判断 	break; } 

在swich结构中的几个重要工作是

• 确定图片那3个Image控件要从哪里移动到哪里，我选择高效的RenderTransform。位置一个有3个-width、0、width。每个控件在每个时刻，个占据一个位置
• 计算不同时间，每个控件Z-Index的正确值。在前面已经指出了层级了。
• 找到需要加载的图片，在合适的时机切换某个Image控件的图片源。经过我的碰壁，发现同一时间全部替换，是一个错误的做法。最后换成了每次点击值加载一张图片。即根据滑动方向，加载下下张。但要注意，在必要时时判断是否超出数组索引。

//左移 P_Cimage.Source = new BitmapImage(new Uri(Urls[Current - 1])); //右移 if(Current + 1 < Urls.Count) {     P_Cimage.Source = new BitmapImage(new Uri(Urls[Current + 1])); } 

使用VisualState可以简化这种管理。我把这种切换设计为3个状态Normal R_Translate L_Translate。在不同状态时，3个图片控件分别占据不同位置，然后根据数据组织的环形结构进行状态切换。

这里比较麻烦的地方在于，状态中的动画没法没法绑定到依赖属性，其次也没法用动态资源进行切换属性值。还是得到逻辑代码中进行控制。

P_BL.RenderTransform.Value.Translate(-P_BC.ActualWidth, 0); P_BC.RenderTransform.Value.Translate(0, 0); P_BR.RenderTransform.Value.Translate(P_BC.ActualWidth, 0);  d4_.To = -P_BC.ActualWidth; d5_.To = 0; d6_.To = P_BC.ActualWidth;  d4.From = 0; d5.From = P_BC.ActualWidth; d6.From = -P_BC.ActualWidth; 

为了响应控件大小变化后，动画元素还能够精确到达所需偏移位置，就要每次点击前微调控件位置。要让Image元素的RenderTransform使用DynamicResource,才能在代码中进行更新位置。全屏后点击下一页，下一页Image控件的偏移量是1920，但求出全屏后，需要的偏移量就小多了，需要根据控件大小动态计算。主要原因是因为这里要使用动画，不然的话，使用布局计算可能是是一个比较好的方式。

<Border x:Name="P_BL" Grid.Column="0" Grid.ColumnSpan="2" Background="LightPink">     <Border.RenderTransform>         <TranslateTransform X="{DynamicResource left}"/>     </Border.RenderTransform>     <Image x:Name="P_Limage"/> </Border> 

完整代码

Generic.xaml

<ResourceDictionary     xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"     xmlns:local="clr-namespace:Pictures"      xmlns:sys="clr-namespace:System;assembly=mscorlib"      xmlns:sys2="http://schemas.microsoft.com/netfx/2009/xaml/presentation">          <!--<local:NegativeValueConverter x:Key="NegativeValueConverter"/>-->     <sys:Double x:Key="left">-1200</sys:Double>     <sys:Double x:Key="right">1200</sys:Double>     <sys2:Duration x:Key="dur">0:0:0.2</sys2:Duration>     <sys2:PowerEase EasingMode="EaseOut" Power="0.3" x:Key="ea"/>       <Style TargetType="{x:Type local:CustomControl2}">         <Setter Property="Template">             <Setter.Value>                 <ControlTemplate TargetType="{x:Type local:CustomControl2}">                     <Border Background="{TemplateBinding Background}"                             BorderBrush="{TemplateBinding BorderBrush}"                             BorderThickness="{TemplateBinding BorderThickness}">                         <Grid>                             <Grid.ColumnDefinitions>                                 <ColumnDefinition/>                                 <ColumnDefinition/>                             </Grid.ColumnDefinitions>                             <Border x:Name="P_Bulkhead" Grid.Column="0" Grid.ColumnSpan="2" Background="White"></Border>                             <Border x:Name="P_BC" Grid.Column="0" Grid.ColumnSpan="2" Background="LightGreen">                                 <Border.RenderTransform>                                     <!--这个始终为零就不需要使用资源了-->                                     <TranslateTransform X="0"/>                                 </Border.RenderTransform>                                 <Image x:Name="P_Cimage"/>                             </Border>                             <Border x:Name="P_BL" Grid.Column="0" Grid.ColumnSpan="2" Background="LightPink">                                 <Border.RenderTransform>                                     <TranslateTransform X="{DynamicResource left}"/>                                 </Border.RenderTransform>                                 <Image x:Name="P_Limage"/>                             </Border>                             <Border x:Name="P_BR" Grid.Column="0" Grid.ColumnSpan="2" Background="LightBlue">                                 <Border.RenderTransform>                                     <TranslateTransform X="{DynamicResource right}"/>                                 </Border.RenderTransform>                                 <Image x:Name="P_Rimage"/>                             </Border>                             <TextBlock Grid.Column="2" Text="{Binding Current, RelativeSource={RelativeSource TemplatedParent}, StringFormat='{}{0}'}"/>                             <Button x:Name="P_Bleft" Opacity="0" Grid.Column="0" Cursor="/Pictures;component/images/left.cur">上一页</Button>                             <Button x:Name="P_Bright" Opacity="0" Grid.Column="1" Cursor="/Pictures;component/images/right.cur">下一页</Button>                          </Grid>                         <VisualStateManager.VisualStateGroups>                             <VisualStateGroup x:Name="group1">                                 <VisualState x:Name="Normal">                                     <Storyboard>                                         <DoubleAnimation x:Name="d1_" Storyboard.TargetName="P_BL" Storyboard.TargetProperty="(Border.RenderTransform).(TranslateTransform.X)" Duration="0:0:0" To="{DynamicResource left}"/>                                         <DoubleAnimation x:Name="d2_" Storyboard.TargetName="P_BC" Storyboard.TargetProperty="(Border.RenderTransform).(TranslateTransform.X)" Duration="0:0:0" To="0"/>                                         <DoubleAnimation x:Name="d3_" Storyboard.TargetName="P_BR" Storyboard.TargetProperty="(Border.RenderTransform).(TranslateTransform.X)" Duration="0:0:0" To="{DynamicResource right}"/>                                     </Storyboard>                                 </VisualState>                                 <VisualState x:Name="R_Translate">                                     <Storyboard>                                         <DoubleAnimation x:Name="d4_" Storyboard.TargetName="P_BC" Storyboard.TargetProperty="(Border.RenderTransform).(TranslateTransform.X)" Duration="0:0:0" To="{DynamicResource left}"/>                                         <DoubleAnimation x:Name="d5_" Storyboard.TargetName="P_BR" Storyboard.TargetProperty="(Border.RenderTransform).(TranslateTransform.X)" Duration="0:0:0" To="0"/>                                         <DoubleAnimation x:Name="d6_" Storyboard.TargetName="P_BL" Storyboard.TargetProperty="(Border.RenderTransform).(TranslateTransform.X)" Duration="0:0:0" To="{DynamicResource right}"/>                                     </Storyboard>                                 </VisualState>                                 <VisualState x:Name="L_Translate">                                     <Storyboard>                                         <DoubleAnimation x:Name="d7_" Storyboard.TargetName="P_BR" Storyboard.TargetProperty="(Border.RenderTransform).(TranslateTransform.X)" Duration="0:0:0" To="{DynamicResource left}"/>                                         <DoubleAnimation x:Name="d8_" Storyboard.TargetName="P_BL" Storyboard.TargetProperty="(Border.RenderTransform).(TranslateTransform.X)" Duration="0:0:0" To="0"/>                                         <DoubleAnimation x:Name="d9_" Storyboard.TargetName="P_BC" Storyboard.TargetProperty="(Border.RenderTransform).(TranslateTransform.X)" Duration="0:0:0" To="{DynamicResource right}"/>                                     </Storyboard>                                 </VisualState>                                 <VisualStateGroup.Transitions>                                     <VisualTransition To="Normal">                                         <Storyboard>                                             <DoubleAnimation x:Name="d1" Storyboard.TargetName="P_BL" EasingFunction="{StaticResource ea}" Storyboard.TargetProperty="(Border.RenderTransform).(TranslateTransform.X)" Duration="{StaticResource dur}" To="{DynamicResource left}"/>                                             <DoubleAnimation x:Name="d2" Storyboard.TargetName="P_BC" EasingFunction="{StaticResource ea}" Storyboard.TargetProperty="(Border.RenderTransform).(TranslateTransform.X)" Duration="{StaticResource dur}" To="0"/>                                             <DoubleAnimation x:Name="d3" Storyboard.TargetName="P_BR" EasingFunction="{StaticResource ea}" Storyboard.TargetProperty="(Border.RenderTransform).(TranslateTransform.X)" Duration="{StaticResource dur}" To="{DynamicResource right}"/>                                         </Storyboard>                                     </VisualTransition>                                     <VisualTransition To="R_Translate">                                         <Storyboard>                                             <DoubleAnimation x:Name="d4" Storyboard.TargetName="P_BC" EasingFunction="{StaticResource ea}" Storyboard.TargetProperty="(Border.RenderTransform).(TranslateTransform.X)" Duration="{StaticResource dur}" To="{DynamicResource left}"/>                                             <DoubleAnimation x:Name="d5" Storyboard.TargetName="P_BR" EasingFunction="{StaticResource ea}" Storyboard.TargetProperty="(Border.RenderTransform).(TranslateTransform.X)" Duration="{StaticResource dur}" To="0"/>                                             <DoubleAnimation x:Name="d6" Storyboard.TargetName="P_BL" EasingFunction="{StaticResource ea}" Storyboard.TargetProperty="(Border.RenderTransform).(TranslateTransform.X)" Duration="{StaticResource dur}" To="{DynamicResource right}"/>                                         </Storyboard>                                     </VisualTransition>                                     <VisualTransition To="L_Translate">                                         <Storyboard>                                             <DoubleAnimation x:Name="d7" Storyboard.TargetName="P_BR" EasingFunction="{StaticResource ea}" Storyboard.TargetProperty="(Border.RenderTransform).(TranslateTransform.X)" Duration="{StaticResource dur}" To="{DynamicResource left}"/>                                             <DoubleAnimation x:Name="d8" Storyboard.TargetName="P_BL" EasingFunction="{StaticResource ea}" Storyboard.TargetProperty="(Border.RenderTransform).(TranslateTransform.X)" Duration="{StaticResource dur}" To="0"/>                                             <DoubleAnimation x:Name="d9" Storyboard.TargetName="P_BC" EasingFunction="{StaticResource ea}" Storyboard.TargetProperty="(Border.RenderTransform).(TranslateTransform.X)" Duration="{StaticResource dur}" To="{DynamicResource right}"/>                                         </Storyboard>                                     </VisualTransition>                                 </VisualStateGroup.Transitions>                             </VisualStateGroup>                         </VisualStateManager.VisualStateGroups>                     </Border>                 </ControlTemplate>             </Setter.Value>         </Setter>     </Style> </ResourceDictionary>  

后台代码

namespace Pictures {     [TemplatePart(Name = "P_Bleft",Type = typeof(Button))]     [TemplatePart(Name = "P_Bright", Type = typeof(Button))]     [TemplatePart(Name = "P_Limage", Type = typeof(Image))]     [TemplatePart(Name = "P_Cimage", Type = typeof(Image))]     [TemplatePart(Name = "P_Rimage", Type = typeof(Image))]     [TemplatePart(Name = "P_BC", Type = typeof(Border))]     [TemplatePart(Name = "P_BL", Type = typeof(Border))]     [TemplatePart(Name = "P_BR", Type = typeof(Border))]     [TemplatePart(Name = "P_Bulkhead",Type =typeof(Border))]     [TemplatePart(Name = "P_BC", Type = typeof(Border))]     [TemplatePart(Name = "P_BL", Type = typeof(Border))]     [TemplatePart(Name = "P_BR", Type = typeof(Border))]     [TemplateVisualState(GroupName = "group1",Name = "L_Translate")]     [TemplateVisualState(GroupName = "group1", Name = "R_Translate")]     [TemplateVisualState(GroupName = "group1", Name = "Normal")]     [TemplatePart(Name = "d1", Type = typeof(DoubleAnimation))]     [TemplatePart(Name = "d2", Type = typeof(DoubleAnimation))]     [TemplatePart(Name = "d3", Type = typeof(DoubleAnimation))]     [TemplatePart(Name = "d4", Type = typeof(DoubleAnimation))]     [TemplatePart(Name = "d5", Type = typeof(DoubleAnimation))]     [TemplatePart(Name = "d6", Type = typeof(DoubleAnimation))]     [TemplatePart(Name = "d7", Type = typeof(DoubleAnimation))]     [TemplatePart(Name = "d8", Type = typeof(DoubleAnimation))]     [TemplatePart(Name = "d9", Type = typeof(DoubleAnimation))]     [TemplatePart(Name = "d1_", Type = typeof(DoubleAnimation))]     [TemplatePart(Name = "d2_", Type = typeof(DoubleAnimation))]     [TemplatePart(Name = "d3_", Type = typeof(DoubleAnimation))]     [TemplatePart(Name = "d4_", Type = typeof(DoubleAnimation))]     [TemplatePart(Name = "d5_", Type = typeof(DoubleAnimation))]     [TemplatePart(Name = "d6_", Type = typeof(DoubleAnimation))]     [TemplatePart(Name = "d7_", Type = typeof(DoubleAnimation))]     [TemplatePart(Name = "d8_", Type = typeof(DoubleAnimation))]     [TemplatePart(Name = "d9_", Type = typeof(DoubleAnimation))]     public class CustomControl2 : Control     {         public const string L_Translate = "L_Translate";         public const string R_Translate = "R_Translate";         public const string Normal = "Normal";         static CustomControl2()         {             DefaultStyleKeyProperty.OverrideMetadata(typeof(CustomControl2), new FrameworkPropertyMetadata(typeof(CustomControl2)));         }          /// <summary>         /// 当前页         /// </summary>         public int Current         {             get { return (int)GetValue(CurrentProperty); }             set { SetValue(CurrentProperty, value); }         }          public static readonly DependencyProperty CurrentProperty =             DependencyProperty.Register("Current", typeof(int), typeof(CustomControl2), new PropertyMetadata(0));          /// <summary>         /// 图片         /// </summary>         public ObservableCollection<string> Urls         {             get { return (ObservableCollection<string>)GetValue(UrlsProperty); }             set { SetValue(UrlsProperty, value); }         }         public static readonly DependencyProperty UrlsProperty =             DependencyProperty.Register("Urls", typeof(ObservableCollection<string>), typeof(CustomControl2), new PropertyMetadata(null, OnUrlsChanged));         private static void OnUrlsChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)         {             CustomControl2 control = d as CustomControl2;             if (control != null)             {                 control.OnUrlsChanged((ObservableCollection<string>)e.OldValue, (ObservableCollection<string>)e.NewValue);             }         }          private void OnUrlsChanged(ObservableCollection<string> oldValue, ObservableCollection<string> newValue)         {             Current = 0;             BeginStoryBoard(0, true);         }          public override void OnApplyTemplate()         {             base.OnApplyTemplate();             Button P_Bleft = (Button)GetTemplateChild("P_Bleft");             Button P_Bright = (Button)GetTemplateChild("P_Bright");             //隔板             Border P_Bulkhead = (Border)GetTemplateChild("P_Bulkhead");             P_Bleft.SetValue(Canvas.ZIndexProperty, 4);             P_Bright.SetValue(Canvas.ZIndexProperty, 4);             P_Bulkhead.SetValue(Canvas.ZIndexProperty, 1);             P_Bleft.Click += (s, e) => ToPage(-1);             P_Bright.Click += (s, e) => ToPage(1);         }          private void ToPage(int offset)         {             if (Current==0 && offset<0)             {                 return;             }             if (Current>=Urls.Count-1 && offset>0)             {                 return;             }             Current += offset;              BeginStoryBoard(offset);         }          private void BeginStoryBoard(int offset,bool init=false)         {             Image P_Cimage = (Image)GetTemplateChild("P_Cimage");             Image P_Limage = (Image)GetTemplateChild("P_Limage");             Image P_Rimage = (Image)GetTemplateChild("P_Rimage");             Border P_BC = (Border)GetTemplateChild("P_BC");             Border P_BL = (Border)GetTemplateChild("P_BL");             Border P_BR = (Border)GetTemplateChild("P_BR");             Application.Current.Resources["left"]= -P_BC.ActualWidth;             Application.Current.Resources["right"] = P_BC.ActualWidth;             //当前页             int state = (Current) % 3;              //由于动画不能绑定To属性，只能在代码中动态调整             #region 调整状态             DoubleAnimation d1 = (DoubleAnimation)GetTemplateChild("d1");             DoubleAnimation d2 = (DoubleAnimation)GetTemplateChild("d2");             DoubleAnimation d3 = (DoubleAnimation)GetTemplateChild("d3");             DoubleAnimation d4 = (DoubleAnimation)GetTemplateChild("d4");             DoubleAnimation d5 = (DoubleAnimation)GetTemplateChild("d5");             DoubleAnimation d6 = (DoubleAnimation)GetTemplateChild("d6");             DoubleAnimation d7 = (DoubleAnimation)GetTemplateChild("d7");             DoubleAnimation d8 = (DoubleAnimation)GetTemplateChild("d8");             DoubleAnimation d9 = (DoubleAnimation)GetTemplateChild("d9");             DoubleAnimation d1_ = (DoubleAnimation)GetTemplateChild("d1_");             DoubleAnimation d2_ = (DoubleAnimation)GetTemplateChild("d2_");             DoubleAnimation d3_ = (DoubleAnimation)GetTemplateChild("d3_");             DoubleAnimation d4_ = (DoubleAnimation)GetTemplateChild("d4_");             DoubleAnimation d5_ = (DoubleAnimation)GetTemplateChild("d5_");             DoubleAnimation d6_ = (DoubleAnimation)GetTemplateChild("d6_");             DoubleAnimation d7_ = (DoubleAnimation)GetTemplateChild("d7_");             DoubleAnimation d8_ = (DoubleAnimation)GetTemplateChild("d8_");             DoubleAnimation d9_ = (DoubleAnimation)GetTemplateChild("d9_");             d1.To = -P_BC.ActualWidth;             d2.To = 0;             d3.To = P_BC.ActualWidth;             d4.To = -P_BC.ActualWidth;             d5.To = 0;             d6.To = P_BC.ActualWidth;             d7.To = -P_BC.ActualWidth;             d8.To = 0;             d9.To = P_BC.ActualWidth;             d1_.To = -P_BC.ActualWidth;             d2_.To = 0;             d3_.To = P_BC.ActualWidth;             d4_.To = -P_BC.ActualWidth;             d5_.To = 0;             d6_.To = P_BC.ActualWidth;             d7_.To = -P_BC.ActualWidth;             d8_.To = 0;             d9_.To = P_BC.ActualWidth;             #endregion              switch (state)             {                 case 0:                     P_BC.SetValue(Canvas.ZIndexProperty, 3);                     if (init)                     {                         if (Urls.Count>0)                         {                             P_Cimage.Source = new BitmapImage(new Uri(Urls[0]));                         }                         if (Urls.Count > 1)                         {                             P_Rimage.Source = new BitmapImage(new Uri(Urls[1]));                         }                         P_BL.RenderTransform.Value.Translate(-P_BC.ActualWidth, 0);                         P_BC.RenderTransform.Value.Translate(0, 0);                         P_BR.RenderTransform.Value.Translate(P_BC.ActualWidth, 0);                     }                     else                     {                         if (offset==1)                         {                             //右移                             if(Current + 1 < Urls.Count)                             {                                 P_Rimage.Source = new BitmapImage(new Uri(Urls[Current + 1]));                             }                             P_BL.SetValue(Canvas.ZIndexProperty, 2);                             P_BR.SetValue(Canvas.ZIndexProperty, 0);                             d1.From = 0;                             d2.From = P_BC.ActualWidth;                             d3.From = -P_BC.ActualWidth;                         }                         if (offset==-1)                         {                             //左移                             if (Current>0)                             {                                 P_Limage.Source = new BitmapImage(new Uri(Urls[Current - 1]));                             }                             P_BL.SetValue(Canvas.ZIndexProperty, 0);                             P_BR.SetValue(Canvas.ZIndexProperty, 2);                             d1.From = P_BC.ActualWidth;                             d2.From = -P_BC.ActualWidth;                             d3.From = 0;                         }                     }                     VisualStateManager.GoToState(this, Normal, true);                     break;                 case 1:                     P_BR.SetValue(Canvas.ZIndexProperty, 3);                     if (offset == 1)                     {                         //右移                         if (Current+1<Urls.Count)                         {                             P_Limage.Source = new BitmapImage(new Uri(Urls[Current + 1]));                         }                         P_BC.SetValue(Canvas.ZIndexProperty, 2);                         P_BL.SetValue(Canvas.ZIndexProperty, 0);                         d4.From = 0;                         d5.From = P_BC.ActualWidth;                         d6.From = -P_BC.ActualWidth;                     }                     if (offset == -1)                     {                         //左移                         P_Cimage.Source = new BitmapImage(new Uri(Urls[Current - 1]));                         P_BC.SetValue(Canvas.ZIndexProperty, 0);                         P_BL.SetValue(Canvas.ZIndexProperty, 2);                         d4.From = P_BC.ActualWidth;                         d5.From = -P_BC.ActualWidth;                         d6.From = 0;                     }                     VisualStateManager.GoToState(this, R_Translate, true);                     break;                 case 2:                     P_BL.SetValue(Canvas.ZIndexProperty, 3);                     if (offset == 1)                     {                         //右移                         if(Current + 1 < Urls.Count)                         {                             P_Cimage.Source = new BitmapImage(new Uri(Urls[Current + 1]));                         }                         P_BC.SetValue(Canvas.ZIndexProperty, 0);                         P_BR.SetValue(Canvas.ZIndexProperty, 2);                         d7.From=0;                         d8.From = P_BC.ActualWidth;                         d9.From=-P_BC.ActualWidth;                     }                     if (offset == -1)                     {                         //左移                         P_Rimage.Source = new BitmapImage(new Uri(Urls[Current - 1]));                         P_BC.SetValue(Canvas.ZIndexProperty, 2);                         P_BR.SetValue(Canvas.ZIndexProperty, 0);                         d7.From = P_BC.ActualWidth;                         d8.From = -P_BC.ActualWidth;                         d9.From = 0;                     }                     VisualStateManager.GoToState(this, L_Translate, true);                     break;             }         }     } }