如何使用带有 CollectionViewSource 的增量加载集合来对 UWP 中的列表视图项进行分组？

Question

我跟进了 IncrementalLoadingCollection 的这个示例，并创建了一个具有增量加载集合（无限滚动）的应用程序。

XAML:

<ListView x:Name="PeopleListView">
    <ListView.ItemTemplate>
        <DataTemplate x:DataType="local:Person">
            <TextBlock Text="{x:Bind Name}" />
        </DataTemplate>
    </ListView.ItemTemplate>
</ListView>

C#:

public class Person
{
    public string Name { get; set; }
}

public class PeopleSource : IIncrementalSource<Person>
{
    private readonly List<Person> people;

    public PeopleSource()
    {
        // Populate people
        ...
    }
    public async Task<IEnumerable<Person>> GetPagedItemsAsync(int pageIndex, int pageSize)
    {
        // Gets and returns items from the collection according to pageIndex and pageSize parameters
        ...
    }
}    

var collection = new IncrementalLoadingCollection<PeopleSource, Person>();
PeopleListView.ItemsSource = collection;

但现在我还需要对项目进行分组，例如按名称的长度分组。另外，使用 CollectionViewSource 这个例子，我创建了一个我期望的例子：

XAML:

<Grid.Resources>
    <CollectionViewSource x:Name="groupInfoCVS" IsSourceGrouped="true" />
</Grid.Resources>
<ListView x:Name="PeopleListView" ItemsSource="{Binding Source={StaticResource groupInfoCVS}}">
    ...
</ListView>

C#:

public string Name { get; set; }

// Populate people
...

var result =
from t in people
group t by t.Name.Length into g
orderby g.Key
select g;

groupInfoCVS.Source = result;

问题是我需要使用增量加载并对项目进行分组，我找不到将 IncrementalLoadingCollection 与 CollectionViewSource 一起使用的方法。有谁知道如何做到这一点或可以提出解决方案？感激不尽。

Answer 1

How to use Incremental Loading Collection with CollectionViewSource to group list view items in UWP?

我不得不说，IncrementalLoadingCollection 不适用于 CollectionViewSource。它们都需要直接设置为 ListView 的 ItemsSource 才能工作。因为他们需要检测listview Interaction.

因此，根据您的要求，我们建议收听列表视图 ViewChanged 并手动添加更多项目。

例如

private void PeopleListView_Loaded(object sender, RoutedEventArgs e)
{
    if (!(PeopleListView.ItemsPanelRoot is ItemsStackPanel itemsStackPanel)) return;
    var _itemsStackPanel = itemsStackPanel;
    var _scrollViewer = MyFindDataGridChildOfType<ScrollViewer>(PeopleListView);
    // This event handler loads more items when scrolling.
    _scrollViewer.ViewChanged += (o, eventArgs) =>
    {
        if (eventArgs.IsIntermediate) return;
        double distanceFromBottom = itemsStackPanel.ActualHeight - _scrollViewer.VerticalOffset - _scrollViewer.ActualHeight;
        if (distanceFromBottom < 10) // 10 is an arbitrary number
        {
            for (int i = 1; i <= 50; i++)
            {
                var p = new Person { Name = "Person " + i };
                _people.Add(p);
                var result =
                            from t in _people
                            group t by t.Name.Length into g
                            orderby g.Key
                            select g;

                groupInfoCVS.Source = result;
                PeopleListView.ItemsSource = groupInfoCVS.View;
            }
        }
    };
}

如何使用带有 CollectionViewSource 的增量加载集合来对 UWP 中的列表视图项进行分组？

How to use Incremental Loading Collection with CollectionViewSource to group list view items in UWP?

c#

windows

listview

visual-studio

uwp