在windows8.1中分组列表视图不显示所有数据

大家好，我遵循这个示例MSDN组项列表框但由于某种原因，只有第一组数据显示在屏幕上，不能滚动。

当我运行应用程序时，屏幕只显示"项目1"作为标题，然后在它下面显示5个活动，但不显示其余的数据。我无法弄清楚是否是高度或滚动不工作，并显示其余组(项目2，项目3等)。

如果有人能看到任何明显的错误，我正在犯请让我知道?

提前谢谢你。

MainPage.xaml

<Page
x:Class="TestWin._1.MainPage"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="using:TestWin._1"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d"
Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
<Page.Resources>
    <CollectionViewSource x:Name="cvsActivities" IsSourceGrouped="True">
    </CollectionViewSource>
    <CollectionViewSource x:Name="cvsProjects" IsSourceGrouped="True" ItemsPath="Activities"/>
    <local:ListGroupStyleSelector x:Key="listGroupStyleSelector"/>
</Page.Resources>

<Grid Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
    <Grid.ColumnDefinitions>
        <ColumnDefinition Width="10"/>
        <ColumnDefinition/>
    </Grid.ColumnDefinitions>
    <ListView ItemsSource="{Binding Source={StaticResource cvsActivities}}"
      ItemTemplate="{StaticResource listViewItemTemplate}"
      GroupStyleSelector="{StaticResource listGroupStyleSelector}"
      Margin="120" Width="320" Height="9000"
              />
    <GridView ItemsSource="{Binding Source={StaticResource cvsProjects}}" 
      Margin="0,10,0,0"  Grid.Column="1" ScrollViewer.VerticalScrollMode="Auto">
        <GridView.ItemTemplate>
            <DataTemplate>
                <StackPanel Margin="20">
                    <TextBlock Text="{Binding Name}" FontWeight="Bold" 
                               Style="{StaticResource BaseTextBlockStyle}"/>
                    <TextBlock Text="{Binding DueDate}" TextWrapping="NoWrap" 
                               Style="{StaticResource BodyTextBlockStyle}" />
                    <CheckBox Content="Complete" IsChecked="{Binding Complete}" 
                              IsEnabled="False"/>
                </StackPanel>
            </DataTemplate>
        </GridView.ItemTemplate>
        <GridView.ItemsPanel>
            <ItemsPanelTemplate>
                <ItemsWrapGrid MaximumRowsOrColumns="3"/>
            </ItemsPanelTemplate>
        </GridView.ItemsPanel>

MainPage.cs

using System;


namespace TestWin._1
{
/// <summary>
/// An empty page that can be used on its own or navigated to within a Frame.
/// </summary>
public sealed partial class MainPage : Page
{
    DateTime startDate;
    public MainPage()
    {
        this.InitializeComponent();
    }
    /// <summary>
    /// Invoked when this page is about to be displayed in a Frame.
    /// </summary>
    /// <param name="e">Event data that describes how this page was reached.  The Parameter
    /// property is typically used to configure the page.</param>
    protected override void OnNavigatedTo(NavigationEventArgs e)
    {
        DateTime.TryParse("1/1/2014", out startDate);
        PopulateProjects();
        PopulateActivities();
    }
    private void PopulateActivities()
    {
        List<Activity> Activities = new List<Activity>();
        Activities.Add(new Activity()
        {
            Name = "Activity 1",
            Complete = true,
            DueDate = startDate.AddDays(4),
            Project = "Project 1"
        });
        Activities.Add(new Activity()
        {
            Name = "Activity 2",
            Complete = true,
            DueDate = startDate.AddDays(5),
            Project = "Project 1"
        });
        Activities.Add(new Activity()
        {
            Name = "Activity 3",
            Complete = false,
            DueDate = startDate.AddDays(7),
            Project = "Project 1"
        });
        Activities.Add(new Activity()
        {
            Name = "Activity 4",
            Complete = false,
            DueDate = startDate.AddDays(9),
            Project = "Project 1"
        });
        Activities.Add(new Activity()
        {
            Name = "Activity 5",
            Complete = false,
            DueDate = startDate.AddDays(14),
            Project = "Project 1"
        });
        Activities.Add(new Activity()
        {
            Name = "Activity A",
            Complete = true,
            DueDate = startDate.AddDays(2),
            Project = "Project 2"
        });
        Activities.Add(new Activity()
        {
            Name = "Activity B",
            Complete = false,
            DueDate = startDate.AddDays(4),
            Project = "Project 2"
        });
        Activities.Add(new Activity()
        {
            Name = "Activity C",
            Complete = true,
            DueDate = startDate.AddDays(5),
            Project = "Project 2"
        });
        Activities.Add(new Activity()
        {
            Name = "Activity D",
            Complete = false,
            DueDate = startDate.AddDays(9),
            Project = "Project 2"
        });
        Activities.Add(new Activity()
        {
            Name = "Activity E",
            Complete = false,
            DueDate = startDate.AddDays(18),
            Project = "Project 2"
        });
        var result = from act in Activities group act by act.Project into grp orderby grp.Key select grp;
        cvsActivities.Source = result;
    }
    private void PopulateProjects()
    {
        List<Project> Projects = new List<Project>();
        Project newProject = new Project();
        newProject.Name = "Project 1";
        newProject.Activities.Add(new Activity() { Name = "Activity 1", Complete = true, DueDate = startDate.AddDays(4) });
        newProject.Activities.Add(new Activity() { Name = "Activity 2", Complete = true, DueDate = startDate.AddDays(5) });
        newProject.Activities.Add(new Activity() { Name = "Activity 3", Complete = false, DueDate = startDate.AddDays(7) });
        newProject.Activities.Add(new Activity() { Name = "Activity 4", Complete = false, DueDate = startDate.AddDays(9) });
        newProject.Activities.Add(new Activity() { Name = "Activity 5", Complete = false, DueDate = startDate.AddDays(14) });
        Projects.Add(newProject);
        newProject = new Project();
        newProject.Name = "Project 2";
        newProject.Activities.Add(new Activity() { Name = "Activity A", Complete = true, DueDate = startDate.AddDays(2) });
        newProject.Activities.Add(new Activity() { Name = "Activity B", Complete = false, DueDate = startDate.AddDays(3) });
        newProject.Activities.Add(new Activity() { Name = "Activity C", Complete = true, DueDate = startDate.AddDays(5) });
        newProject.Activities.Add(new Activity() { Name = "Activity D", Complete = false, DueDate = startDate.AddDays(9) });
        newProject.Activities.Add(new Activity() { Name = "Activity E", Complete = false, DueDate = startDate.AddDays(18) });
        Projects.Add(newProject);
        newProject = new Project();
        newProject.Name = "Project 3";
        Projects.Add(newProject);
        cvsProjects.Source = Projects;
    }
}
public class ListGroupStyleSelector : GroupStyleSelector
{
    protected override GroupStyle SelectGroupStyleCore(object group, uint level)
    {
        return (GroupStyle)App.Current.Resources["listViewGroupStyle"];
    }
}
public class Project
{
    public Project()
    {
        Activities = new ObservableCollection<Activity>();
    }
    public string Name { get; set; }
    public ObservableCollection<Activity> Activities { get; private set; }
}
public class Activity
{
    public string Name { get; set; }
    public DateTime DueDate { get; set; }
    public bool Complete { get; set; }
    public string Project { get; set; }
}

}

<Grid.ColumnDefinitions>
    <ColumnDefinition Width="10"/>
    <ColumnDefinition/>
</Grid.ColumnDefinitions>