CODEWITHSUNDEEP
c#.netxamluwpdata-virtualization
marsalal1014
marsalal1014

Reputation: 1907

ISupportIncrementalLoading does not work until I scroll in GridView

I've implemented ISupportIncrementalLoading to load a lot of items in a list as the user scrolls. When I load the view, its empty and it will only load more data until I scroll the list.

This is the class that implements it 

  public class DeviceListDataSource<T> : ObservableCollection<T>, ISupportIncrementalLoading
    where T : class
{
    public int LastItem = 0;

    public bool HasMoreItems => hasMoreItems;

    private int currentPage;

    private List<T> source;

    private bool hasMoreItems;

    public DeviceListDataSource(List<T> source)
    {
        this.source = source;
        hasMoreItems = true;
    }

    public async Task<IEnumerable<T>> GetPagedItems(int pageIndex, int pageSize)
    {
        return await Task.Run(() =>
        {
            var result = (from p in source
                          select p).Skip(pageIndex * pageSize).Take(pageSize);

            return result;
        });

    }

    public IAsyncOperation<LoadMoreItemsResult> LoadMoreItemsAsync(uint count)
    {
        var dispatcher = Window.Current.Dispatcher;
        return Task.Run(
       async () =>
       {
           var result = await GetPagedItems(currentPage++, (int) count);

           if (result == null || result.Count() == 0)
           {
               hasMoreItems = false;
           }
           else
           {

               await dispatcher.RunAsync(
                   CoreDispatcherPriority.Normal,
                   () =>
                   {
                       foreach (T item in result)
                       {
                           Add(item);
                       }
                   });
           }

           return new LoadMoreItemsResult() { Count = (uint)currentPage };

       }).AsAsyncOperation();
    }
}

}

And in the view model, I assign it to the variable that is bound to the list view in the xaml view: Items = new DeviceListDataSource<DataObject>(source);

Is there a way to load the first X items in the list? Its always 0 when it first loads and it remains that way until I scroll. Many thanks!

Upvotes: 1

Views: 163

Answers (1)

Sunteen Wu
Sunteen Wu

Reputation: 10627

Is there a way to load the first X items in the list?

You already had LoadMoreItemsAsync method implemented in the DeviceListDataSource class, just invoke this method to manually loading X items code behind when initial loading. For example:

DeviceListDataSource<Data> Items = new DeviceListDataSource<Data>(source);
Items.LoadMoreItemsAsync(10);

Upvotes: 2

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