扩展GridView控件——为内容项添加拖放及分组功能

引言

相信你们对GridView都不陌生，是很是有用的控件，用于平铺有序的显示多个内容项。打开任何WinRT应用或者是微软合做商的网站，都会在APP中发现GridView的使用。“Tiles”提供了一个简单易用，平铺方式来组织内容显示。Windows8的开始菜单是最典型的GridView 示例。“开始菜单”显示了系统中安装的全部应用程序，并且支持从新排列。

本文源于咱们项目的开发人员，他们想在项目中提供与GridView相同的用户体验，想要建立类GridView控件。

GridView 能够显示大小不定的内容项，而且以有序的方式显示。若是各个内容项无序，而且内容尺寸大小相同，GirdView还支持拖拽操做。然而，这些功能并非默认提供的，须要编写必定的代码才能实现。

本文主要介绍了扩展GridView控件——称为GridViewEx, GridViewEx主要实现GridView在不一样大小的内容项中的拖拽功能。

背景

首先了解GridView的基本属性和功能，GridView包含一些属性集和 ItemTemplate。为了实现经过拖拽操做执行重排列功能，必须完成如下三件事：

1. 设置AllowDrop属性为true;

2. 设置CanReorderItems 属性值为True;

3. 绑定数据源，该数据源必须支持数据修改或支持重排序。例如，使用ObservableCollection或IList数据源。

<GridView ItemsSource="{Binding}" AllowDrop="True" CanReorderItems="True"> <GridView.ItemTemplate> <DataTemplate> <Border BorderBrush="Aqua" BorderThickness="1" Background="Peru"> <Grid Margin="12"> <Grid.RowDefinitions> <RowDefinition /> <RowDefinition Height="Auto"/> </Grid.RowDefinitions> <TextBlock Text="{Binding}"/> <TextBlock Grid.Row="1">item</TextBlock> </Grid> </Border> </DataTemplate> </GridView.ItemTemplate> </GridView>

扩展后的GridView使用拖拽操做将会很是方便快捷。

GridViewEx 控件

GridViewEx控件弥补了GridView，功能以下：

• 实现Item Panel 拖拽操做，而不是WrapGrid，StackPanel、VirtualizingStackPanel等
• 分组时，实现拖拽功能；

咱们也为GridViewEx增长了新建分组的功能，若是用户将内容项拖到控件左边或右边时会触发新建分组操做。

实现拖拽代码：

 1: public class GridViewEx : GridView

 2: {

 3:  /// <summary>

 4:  /// Initializes a new instance of the <see cref="GridViewEx"/> control.

 5:  /// </summary>

 6:  public GridViewEx()

 7:  {

 8:  // see attached sample

 9:  }

 10: 

 11:  private void GridViewEx_DragItemsStarting(object sender, DragItemsStartingEventArgs e)

 12:  {

 13:  // see attached sample

 14:  }

 15: 

 16:  /// <summary>

 17:  /// Stores dragged items into DragEventArgs.Data.Properties["Items"] value.

 18:  /// Override this method to set custom drag data if you need to.

 19:  /// </summary>

 20:  protected virtual void OnDragStarting(DragItemsStartingEventArgs e)

 21:  {

 22:  // see attached sample

 23:  }

该控件包含几个变量，用来存储拖放内容的索引。OnDragStarting 事件在DragEventArgs.Data.Properties[“Items”] 中存储拖拽的内容。OnDragStarting 须要根据本身的需求重写。

当用户拖拽某一项内容时，须要给用户提示来引导用户将内容放在合适的位置上。标准的GriView对象是经过滑动相邻的内实项来实现的。本文将在GridViewEx中完善此操做。

 1: /// <summary>

 2: /// Shows reoder hints while custom dragging.

 3: /// </summary>

 4: protected override void OnDragOver(DragEventArgs e)

 5: {

 6:  // see attached sample }

 7:  

 8: private int GetDragOverIndex(DragEventArgs e)

 9: {

 10:  // see attached sample 

 11: }

实现拖放代码

首先须要重写GridView.OnDrop方法，该方法会当用户释放某一项内容时触发。重写Ondrop方法，代码以下：

 1: /// <summary>

 2: /// Handles drag and drop for cases when it is not supported by the Windows.UI.Xaml.Controls.GridView control

 3: /// </summary>

 4: protected override async void OnDrop(DragEventArgs e)

 5: {

 6:  // see attached sample

 7: }

 

OnDrop方法主要实现了内容项从源分组移到目标分组的逻辑代码，以及建立新分组的功能。

添加新分组

若是GrideView经过将IsSourceGrouped值为True来绑定CollectionViewSource状况下，GridView提供分组功能，这就意味着分组必须对数据源进行分组，但GridView没有访问数据的权限。所以本文在执行拖放操做时，实现添加新分组功能。GridViewEx.BeforeDrop事件处理此需求，而且提供更多的数据信息，如DragEventArgs数据。

当用户执行拖放操做时，触发BeforeDrop 事件。

 1: /// <summary>

 2: /// Occurs before performing drop operation,

 3: /// </summary>

 4: public event EventHandler<BeforeDropItemsEventArgs> BeforeDrop;

 5: /// <summary>

 6: /// Rises the <see cref="BeforeDrop"/> event.

 7: /// </summary>

 8: /// <param name="e">Event data for the event.</param>

 9: protected virtual void OnBeforeDrop(BeforeDropItemsEventArgs e)

 10: {

 11:  // see attached sample 

 12: }

BeforeDropItemEventArgs包含关于被拖拽的内容项的重要信息，该信息在OnDrop事件中可以使用的。

 1: /// <summary>

 2: /// Provides data for the <see cref="GridViewEx.BeforeDrop"/> event.

 3: /// </summary>

 4: public sealed class BeforeDropItemsEventArgs : System.ComponentModel.CancelEventArgs

 5: {

 6:  /// <summary>

 7:  /// Gets the item which is being dragged.

 8:  /// </summary>

 9:  public object Item

 10:  {

 11:  get;

 12:  }

 13:  /// <summary>

 14:  /// Gets the current item index in the underlying data source.

 15:  /// </summary>

 16:  public int OldIndex

 17:  {

 18:  get;

 19:  }

 20:  /// <summary>

 21:  /// Gets the index in the underlying data source where

 22:  /// the item will be inserted by the drop operation.

 23:  /// </summary>

 24:  public int NewIndex

 25:  {

 26:  get;

 27:  }

 28:  /// <summary>

 29:  /// Gets the bool value determining whether end-user actions requested

 30:  /// creation of the new group in the underlying data source.

 31:  /// This property only makes sense if GridViewEx.IsGrouping property is true.

 32:  /// </summary>

 33:  /// <remarks>

 34:  /// If this property is true, create the new data group and insert it into

 35:  /// the groups collection at the positions, specified by the 

 36:  /// <see cref="BeforeDropItemsEventArgs.NewGroupIndex"/> property value.

 37:  /// Then the <see cref="GridViewEx"/> will insert dragged item

 38:  /// into the newly added group.

 39:  /// </remarks>

 40:  public bool RequestCreateNewGroup

 41:  {

 42:  get;

 43:  }

 44:  /// <summary>

 45:  /// Gets the current item data group index in the underlying data source.

 46:  /// This property only makes sense if GridViewEx.IsGrouping property is true.

 47:  /// </summary>

 48:  public int OldGroupIndex

 49:  {

 50:  get;

 51:  }

 52:  /// <summary>

 53:  /// Gets the data group index in the underlying data source

 54:  /// where the item will be inserted by the drop operation.

 55:  /// This property only makes sense if GridViewEx.IsGrouping property is true.

 56:  /// </summary>

 57:  public int NewGroupIndex

 58:  {

 59:  get;

 60:  }

 61:  /// <summary>

 62:  /// Gets the original <see cref="DragEventArgs"/> data. 

 63:  /// </summary>

 64:  public DragEventArgs DragEventArgs

 65:  {

 66:  get;

 67:  }

 68: }

AllowNewGroup属性肯定用户拖拽某一内容项到控件边界时，是否建立新组。GridView并无提供此功能，在GridViewEX添加此功能。

 1: /// <summary>

 2: /// Gets or sets the value determining whether new group should be created at 

 3: /// dragging the item to the empty space.

 4: /// </summary>

 5: public bool AllowNewGroup

 6: {

 7:  get { return (bool)GetValue(AllowNewGroupProperty); }

 8:  set { SetValue(AllowNewGroupProperty, value); }

 9: }

 10: 

 11: /// <summary>

 12: /// Identifies the <see cref="AllowNewGroup"/> dependency property.

 13: /// </summary>

 14: public static readonly DependencyProperty AllowNewGroupProperty =

 15:  DependencyProperty.Register("AllowNewGroup", typeof(bool),

 16:  typeof(GridViewEx), new PropertyMetadata(false));

为了在拖拽过程当中添加分组，须要将AllowNewGroup属性设置为True。处理GridViewEx.BeforeDrop事件，该事件的参数可以帮助决定单项内容的起始位置和目的位置。在BeforeDrop事件的Handler中，使用 NewGroupIndex 建立新的数据组，并插入到已有组集合。最后，须要实现的扩展GridView控件模板。在用户可拖拽的项目的位置建立新分组，并使用占位符来代替。一旦用户拖某一内容放置到控件的边界时，触发建立新分组，ItemsPresenter的两个边界元素是新组的占位符。

GridViewEx控件模板generic.xaml，以下：

 1: <Style TargetType="local:GridViewEx">

 2:  <Setter Property="Padding" Value="0,0,0,10" />

 3:  <Setter Property="IsTabStop" Value="False" />

 4:  <Setter Property="TabNavigation" Value="Once" />

 5:  <Setter Property="ScrollViewer.HorizontalScrollBarVisibility" Value="Auto"/>

 6:  <Setter Property="ScrollViewer.VerticalScrollBarVisibility" Value="Disabled"/>

 7:  <Setter Property="ScrollViewer.HorizontalScrollMode" Value="Enabled" />

 8:  <Setter Property="ScrollViewer.IsHorizontalRailEnabled" Value="False" />

 9:  <Setter Property="ScrollViewer.VerticalScrollMode" Value="Disabled" />

 10:  <Setter Property="ScrollViewer.IsVerticalRailEnabled" Value="False" />

 11:  <Setter Property="ScrollViewer.ZoomMode" Value="Disabled" />

 12:  <Setter Property="ScrollViewer.IsDeferredScrollingEnabled" Value="False" />

 13:  <Setter Property="ScrollViewer.BringIntoViewOnFocusChange" Value="True" />

 14:  <Setter Property="IsSwipeEnabled" Value="True" />

 15:  <Setter Property="Template">

 16:  <Setter.Value>

 17:  <ControlTemplate TargetType="local:GridViewEx">

 18:  <Border BorderBrush="{TemplateBinding BorderBrush}"

 19:  Background="{TemplateBinding Background}"

 20:  BorderThickness="{TemplateBinding BorderThickness}">

 21:  <ScrollViewer x:Name="ScrollViewer"

 22:  TabNavigation="{TemplateBinding TabNavigation}"

 23:  HorizontalScrollMode="

 24:  {TemplateBinding ScrollViewer.HorizontalScrollMode}"

 25:  HorizontalScrollBarVisibility=

 26:  "{TemplateBinding 

 27:  ScrollViewer.HorizontalScrollBarVisibility}"

 28:  IsHorizontalScrollChainingEnabled=

 29:  "{TemplateBinding 

 30:  ScrollViewer.IsHorizontalScrollChainingEnabled}"

 31:  VerticalScrollMode="

 32:  {TemplateBinding ScrollViewer.VerticalScrollMode}"

 33:  VerticalScrollBarVisibility=

 34:  "{TemplateBinding 

 35:  ScrollViewer.VerticalScrollBarVisibility}"

 36:  IsVerticalScrollChainingEnabled=

 37:  "{TemplateBinding 

 38:  ScrollViewer.IsVerticalScrollChainingEnabled}"

 39:  IsHorizontalRailEnabled="

 40:  {TemplateBinding ScrollViewer.IsHorizontalRailEnabled}"

 41:  IsVerticalRailEnabled="

 42:  {TemplateBinding ScrollViewer.IsVerticalRailEnabled}"

 43:  ZoomMode="{TemplateBinding 

 44:  ScrollViewer.ZoomMode}"

 45:  IsDeferredScrollingEnabled="

 46:  {TemplateBinding ScrollViewer.IsDeferredScrollingEnabled}"

 47:  BringIntoViewOnFocusChange="

 48:  {TemplateBinding ScrollViewer.BringIntoViewOnFocusChange}">

 49:  <StackPanel Orientation="Horizontal">

 50:  <Border Width="60"

 51:  x:Name="NewGroupPlaceHolderFirst"

 52:  Background="Transparent"

 53:  Padding="{TemplateBinding Padding}"

 54:  Visibility="{Binding AllowNewGroup, 

 55:  Converter={StaticResource

 56:  VisibilityConverter},

 57:  RelativeSource={RelativeSource TemplatedParent}}"/>

 58:  <ItemsPresenter

 59:  Header="{TemplateBinding Header}"

 60:  HeaderTemplate="{TemplateBinding HeaderTemplate}"

 61:  HeaderTransitions="{TemplateBinding HeaderTransitions}"

 62:  Padding="{TemplateBinding Padding}"/>

 63:  <Border Width="60"

 64:  x:Name="NewGroupPlaceHolderLast"

 65:  Background="Transparent"

 66:  Padding="{TemplateBinding Padding}"

 67:  Visibility="{Binding AllowNewGroup, 

 68:  Converter={StaticResource

 69:  VisibilityConverter},

 70:  RelativeSource={RelativeSource TemplatedParent}}"/>

 71:  </StackPanel>

 72:  </ScrollViewer>

 73:  </Border>

 74:  </ControlTemplate>

 75:  </Setter.Value>

 76:  </Setter>

 77: </Style>

 

丰富GridViewEx功能

如上所示，咱们已经实现了基本的拖拽操做，与Windows8 开始菜单相似的功能，接下来讨论如何实现如下功能：

• 尺寸大小不定的内容项
• 分组
• 添加新组
• 节省跨会话布局空间

大小不定的内容项

Windows8展现了不一样大小的Tiles，可是目前GridView或GridViewEx还不支持此功能。由于GridView使用WrapGrid做为默认的ItemsPanel，WrapPanel只能建立一种布局，即全部的条目尺寸相同的。所以微软提供了VariableSizedWrapGrid,支持不一样大小块的布局建立。

GridViewEx控件的优点在于可以使用VariableSizedWrapGrid，而且很好的支持拖放操做。为了使用VariableSizedWrapGrid 并显示不一样大小的内容项，必须实现如下功能：

将GridViewEx.ItemsPanel 设置为VariableSizedWrapGrid

在GridView中重写GridView 的PrepareContainerForItemOverride 方法。在该方法中，能够设置Item的RowSpan或ColumnSpan属性来识别内容项的大小。

即生成继承GridViewEx的新控件MyGridView。为何须要扩展GridViewEx控件而不是重写GridViewEx的PrepareContainerForItemOverride方法？由于指定Item尺寸的逻辑必须放在数据模型中，而不是控件内部。

如想将某一项显示较大一点，须要在数据项中建立一个属性返回比1大的整型数值，来设置RowSpanhuoColumnSpan属性。

 1: public class Item

 2: {

 3:  public int Id { get; set; }

 4:  public int ItemSize { get; set; }

 5:  /* */

 6: }

所以，当建立新的内容项，咱们要指定ItemSize属性。若是值为1则代表常规尺寸，若是值为2则代表大尺寸，ColumnSpan属性则设置为2。

 1: /// <summary>

 2: /// This class sets VariableSizedWrapGrid.ColumnSpanProperty for GridViewItem controls, 

 3: /// so that every item can have different size in the VariableSizedWrapGrid.

 4: /// </summary>

 5: public class MyGridView : GridViewSamples.Controls.GridViewEx

 6: {

 7:  // set ColumnSpan according to the business logic

 8:  // (maybe some GridViewSamples.Samples.Item or group properties)

 9:  protected override void PrepareContainerForItemOverride(

 10:  Windows.UI.Xaml.DependencyObject element, object item)

 11:  {

 12:  try

 13:  {

 14:  GridViewSamples.Samples.Item it = item as GridViewSamples.Samples.Item;

 15:  if (it != null)

 16:  {

 17:  element.SetValue(

 18:  Windows.UI.Xaml.Controls.VariableSizedWrapGrid.ColumnSpanProperty, it.ItemSize);

 19:  }

 20:  }

 21:  catch

 22:  {

 23:  element.SetValue(Windows.UI.Xaml.Controls.VariableSizedWrapGrid.ColumnSpanProperty, 1);

 24:  }

 25:  finally

 26:  {

 27:  base.PrepareContainerForItemOverride(element, item);

 28:  }

 29:  }

 30: }

建立MyGridView实例，并绑定到数据集合。

 1: <local:MyGridView AllowDrop="True" CanReorderItems="True"

 2:  CanDragItems="True" IsSwipeEnabled="True"

 3:  ItemsSource="{Binding}"

 4:  ItemTemplate="{StaticResource ItemTemplate}" >

 5:  <GridView.ItemsPanel>

 6:  <ItemsPanelTemplate>

 7:  <VariableSizedWrapGrid ItemHeight="160"

 8:  ItemWidth="160" />

 9:  </ItemsPanelTemplate>

 10:  </GridView.ItemsPanel>

 11:  <GridView.ItemContainerStyle>

 12:  <Style TargetType="GridViewItem">

 13:  <Setter Property="HorizontalContentAlignment"

 14:  Value="Stretch"/>

 15:  <Setter Property="VerticalContentAlignment"

 16:  Value="Stretch"/>

 17:  </Style>

 18:  </GridView.ItemContainerStyle>

 19: </local:MyGridView>

如上所示，咱们将指定内容项的ItemSize属性设置为2，效果如图所示：

分组

使用GridViewEx控件，可以实现添加新分组和拖拽等功能，也是在App中最为常见的功能，实现分组必须完成如下设置：

• 为GridView绑定CollectionViewSource，必须使用支持分组的数据源。CollectionViewSource可视为代理服务器。
• 使用GroupStyle肯定分组结果如何显示，GroupStyle包含Header Tempate及Panel，所以须要指定子项目的排序方式。

在GridViewEx中添加支持不一样大小的内容项，逻辑代码：

 1: <local:MyGridView AllowDrop="True" CanReorderItems="True"

 2:  CanDragItems="True" IsSwipeEnabled="True"

 3:  ItemsSource="{Binding}"

 4:  ItemTemplate="{StaticResource ItemTemplate}" >

 5:  <GridView.ItemsPanel>

 6:  <ItemsPanelTemplate>

 7:  <VirtualizingStackPanel Orientation="Horizontal"/>

 8:  </ItemsPanelTemplate>

 9:  </GridView.ItemsPanel>

 10:  <GridView.GroupStyle>

 11:  <GroupStyle>

 12:  <GroupStyle.HeaderTemplate>

 13:  <DataTemplate>

 14:  <Grid Background="LightGray"

 15:  Margin="0">

 16:  <TextBlock Foreground="Black"

 17:  Margin="10"

 18:  Style="{StaticResource 

 19:  GroupHeaderTextStyle}">

 20:  <Run Text="{Binding Id}"/>

 21:  <Run Text=" group"/>

 22:  </TextBlock>

 23:  </Grid>

 24:  </DataTemplate>

 25:  </GroupStyle.HeaderTemplate>

 26:  

 27:  <GroupStyle.ContainerStyle>

 28:  <Style TargetType="GroupItem">

 29:  <Setter Property="BorderBrush"

 30:  Value="DarkGray"/>

 31:  <Setter Property="BorderThickness"

 32:  Value="2"/>

 33:  <Setter Property="Margin"

 34:  Value="3,0"/>

 35:  </Style>

 36:  </GroupStyle.ContainerStyle>

 37:  

 38:  <GroupStyle.Panel>

 39:  <ItemsPanelTemplate>

 40:  <VariableSizedWrapGrid ItemHeight="160"

 41:  ItemWidth="160" />

 42:  </ItemsPanelTemplate>

 43:  </GroupStyle.Panel>

 44:  </GroupStyle>

 45:  </GridView.GroupStyle>

 46:  

 47:  <GridView.ItemContainerStyle>

 48:  <Style TargetType="GridViewItem">

 49:  <Setter Property="HorizontalContentAlignment"

 50:  Value="Stretch"/>

 51:  <Setter Property="VerticalContentAlignment"

 52:  Value="Stretch"/>

 53:  </Style>

 54:  </GridView.ItemContainerStyle>

 55: </local:MyGridView>

运行演示：

添加新分组

自定义的GridViewEx控件支持新分组的建立，所以须要设置AllowNewGroup为True。其次处理添加新分组的数据层，处理GridViewEx.BeforeDrop 事件。

 1: /// <summary>

 2: /// Creates new CollectionViewSource and updates page DataContext.

 3: /// </summary>

 4: private void UpdateDataContext()

 5: {

 6:  CollectionViewSource source = new CollectionViewSource();

 7:  source.Source = _groups;

 8:  source.ItemsPath = new PropertyPath("Items");

 9:  source.IsSourceGrouped = true;

 10:  this.DataContext = source;

 11: }

 12: // creates new group in the data source,

 13: // if end-user drags item to the new group placeholder

 14: private void MyGridView_BeforeDrop(object sender, Controls.BeforeDropItemsEventArgs e)

 15: {

 16:  if (e.RequestCreateNewGroup)

 17:  {

 18:  // create new group and re-assign datasource 

 19:  Group group = Group.GetNewGroup();

 20:  if (e.NewGroupIndex == 0)

 21:  {

 22:  _groups.Insert(0, group);

 23:  }

 24:  else

 25:  {

 26:  _groups.Add(group);

 27:  }

 28:  UpdateDataContext();

 29:  }

 30: }

也可使用Drop事件删除空分组

 1: // removes empty groups (except the last one)

 2: private void MyGridView_Drop(object sender, DragEventArgs e)

 3: {

 4:  bool needReset = false;

 5:  for (int i = _groups.Count - 1; i >= 0; i--)

 6:  {

 7:  if (_groups[i].Items.Count == 0 && _groups.Count > 1)

 8:  {

 9:  _groups.RemoveAt(i);

 10:  needReset = true;

 11:  }

 12:  }

 13:  if (needReset)

 14:  {

 15:  UpdateDataContext();

 16:  }

 17: }

节省布局空间

Windows8支持挂起或终止功能，为了提供更好的用户体验，咱们继续改善此前实现的功能，当用户离开当前页面，将当前的布局暂存。在本示例中，咱们使用JSON 字符串简化数据序列化。根据已有的数据、数据的大小及需求，以其余格式来保存数据。咱们主要将“业务对象集合”保存。

为了节省布局空间。重写LayoutAwarePage方法：

 1: /// <summary>

 2: /// Populates the page with content passed during navigation. Any saved state is also

 3: /// provided when recreating a page from a prior session.

 4: /// </summary>

 5: /// <param name="navigationParameter">The parameter value passed to

 6: /// <see cref="Frame.Navigate(Type, 

 7: /// Object)"/> when this page was initially requested.

 8: /// </param>

 9: /// <param name="pageState"

 10: /// >A dictionary of state preserved by this page during an earlier

 11: /// session. This will be null the first time a page is visited.</param>

 12: protected override void LoadState(Object navigationParameter,

 13:  Dictionary<String, Object> pageState)

 14: {

 15:  base.LoadState(navigationParameter, pageState);

 16:  if (pageState != null && pageState.Count > 0

 17:  && pageState.ContainsKey("Groups"))

 18:  {

 19:  // restore groups and items from the previously serialized state

 20:  System.Runtime.Serialization.Json.DataContractJsonSerializer rootSer =

 21:  new System.Runtime.Serialization.Json.DataContractJsonSerializer(typeof(List<Group>));

 22:  var stream = new MemoryStream(System.Text.Encoding.UTF8.GetBytes

 23:  ((string)pageState["Groups"]));

 24:  _groups = (List<Group>)rootSer.ReadObject(stream);

 25:  }

 26:  else

 27:  {

 28:  // if we get here for the first time and don't have

 29:  // serialized content, fill groups and items from scratch

 30:  for (int j = 1; j <= 12; j++)

 31:  {

 32:  Group group = Group.GetNewGroup();

 33:  for (int i = 1; i <= 7 + j % 3; i++)

 34:  {

 35:  group.Items.Add(new Item()

 36:  {

 37:  Id = i,

 38:  GroupId = group.Id

 39:  });

 40:  }

 41:  _groups.Add(group);

 42:  }

 43:  }

 44:  UpdateDataContext();

 45: }

 46:  

 47: /// <summary>

 48: /// Preserves state associated with this page in case the application is suspended or the

 49: /// page is discarded from the navigation cache. Values must conform to the serialization

 50: /// requirements of <see cref="SuspensionManager.SessionState"/>.

 51: /// </summary>

 52: /// <param name="pageState">

 53: /// An empty dictionary to be populated with serializable state.</param>

 54: protected override void SaveState(Dictionary<String, Object> pageState)

 55: {

 56:  // save groups and items to JSON string so that 

 57:  // it's possible to restore page state later

 58:  base.SaveState(pageState);

 59:  System.Runtime.Serialization.Json.DataContractJsonSerializer rootSer =

 60:  new System.Runtime.Serialization.Json.DataContractJsonSerializer

 61:  (typeof(List<Group>));

 62:  var stream = new MemoryStream();

 63:  rootSer.WriteObject(stream, _groups);

 64:  string str = System.Text.Encoding.UTF8.GetString(stream.ToArray(),

 65:  0, (int)stream.Length);

 66:  pageState.Add("Groups", str);

 67: }

 68:  

 69: /// <summary>

 70: /// Invoked when this page is about to be displayed in a Frame.

 71: /// </summary>

 72: /// <param name="e">Event data that describes 

 73: /// how this page was reached. The Parameter

 74: /// property is typically used to configure the page.</param>

 75: protected override void OnNavigatedTo(NavigationEventArgs e)

 76: {

 77:  // restore page state

 78:  var frameState =

 79:  GridViewSamples.Common.SuspensionManager.SessionStateForFrame(this.Frame);

 80:  if (frameState.ContainsKey("TilePageData"))

 81:  {

 82:  this.LoadState(e.Parameter,

 83:  (Dictionary<String, Object>)frameState["TilePageData"]);

 84:  }

 85:  else

 86:  {

 87:  this.LoadState(e.Parameter, null);

 88:  }

 89: }

 90:  

 91: protected override void OnNavigatedFrom(NavigationEventArgs e)

 92: {

 93:  // save page state with "TilePageData" key

 94:  var frameState =

 95:  GridViewSamples.Common.SuspensionManager.SessionStateForFrame(this.Frame);

 96:  var pageState = new Dictionary<String, Object>();

 97:  this.SaveState(pageState);

 98:  frameState["TilePageData"] = pageState;

 99: }

总结

GridViewEx控件丰富了GirdView控件功能，改进了基础功能，提高用户体验。到此已经实现了GridView项与Windows8开始菜单具备的相同用户体验，若是你想了解如何在Windows10平台下开发UWP引用，请持续关注下篇文章：如何在Windows10中开发UWP应用

除了 GirdView之外，具有触摸和键盘导航操做的自动或手动平铺布局的控件还有ComponentOne的TileControl为WinForms ，它不但提供自适应Windows8的样式布局，还具备相似Windows8风格的交互体验和灵活便捷的定制能力。

原文连接：http://www.codeproject.com/Articles/536519/Extending-GridView-with-Drag-and-Drop-for-Grouping