向下滚动并更新 Listview C#

Question

I have a ListView in my UWP app.

This is my code:

<ListView x:Name="viewMedias" SelectionMode="None" VirtualizingStackPanel.VirtualizationMode="Recycling" ScrollViewer.HorizontalScrollMode="Disabled" ScrollViewer.VerticalScrollMode="Auto">
        ......
</ListView>

Now, how can I receive an event when this ListView scrolls to nearly end? I want to Update ItemsSource to add new Items to bottom of the ListView.

Answer 1

Welcome to StackOverflow! What you want to achieve is called Incremental Loading. You don't have to implement it by your self - just check existing solutions. Windows Community Toolkit has IncrementalLoadingCollection helpers that can help you. You can check demo in their sample app: Windows Community Toolkit Sample App in Windows Store (go to helpers > Incremental Loading Collection ). Here is some sample code from this app:

// Defines a data source whose data can be loaded incrementally.
using Microsoft.Toolkit.Uwp;

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

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

    public PeopleSource()
    {
        // Creates an example collection.
        _people = new List<Person>();

        for (int i = 1; i <= 200; i++)
        {
            var p = new Person { Name = "Person " + i };
            _people.Add(p);
        }
    }

    public async Task<IEnumerable<Person>> GetPagedItemsAsync(int pageIndex, int pageSize)
    {
        // Gets items from the collection according to pageIndex and pageSize parameters.
        var result = (from p in _people
                      select p).Skip(pageIndex * pageSize).Take(pageSize);

        // Simulates a longer request...
        await Task.Delay(1000);

        return result;
    }
}

// IncrementalLoadingCollection can be bound to a GridView or a ListView. In this case it is a ListView called PeopleListView.

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

PeopleListView.ItemsSource = collection;

// Binds the collection to the page DataContext in order to use its IsLoading and HasMoreItems properties.
DataContext = collection;

// XAML UI Element
<TextBlock Text="{Binding IsLoading, Converter={StaticResource StringFormatConverter}, ConverterParameter='Is Loading: {0}'}" />
<TextBlock Text="{Binding HasMoreItems, Converter={StaticResource StringFormatConverter}, ConverterParameter='Has More Items: {0}'}" />