CollectionView load more when scrolling up

Question

CollectionView load more when scrolling up

Stesvis 1,041

Hello,

is it possible to implement the "load more" functionality in a CollectionView when you scroll up?

I implemented this approach on several occasions:
https://learn.microsoft.com/en-us/xamarin/xamarin-forms/user-interface/collectionview/populate-data#load-data-incrementally

But in every scenario I needed to load more when i reached the bottom (or the right end for horizontal collections).

Now i am implementing something like a chat page, where I load the latest N messages, and I need to load more when i scroll up instead.
I am unable to figure out a way to do this, as it only seems to work for scrolling down.

The other option is to use the Syncfusion SfListView which has that option, but i'd prefer to keep the CollectionView.

Any advice greatly appreciated.

Thanks

JarvanZhang 23,971

The CollectionView class provides the RemainingItemsThreshold and RemainingItemsThresholdReachedCommand properties which could used to load the data incrementally.

   <CollectionView ItemsSource="{Binding DataCollection}" RemainingItemsThreshold="0" RemainingItemsThresholdReachedCommand="{Binding ItemTresholdReachedCommand}">  
       <CollectionView.ItemTemplate>  
           <DataTemplate>  
               ...  
           </DataTemplate>  
       </CollectionView.ItemTemplate>  
   </CollectionView>  
     
   <ActivityIndicator   
       IsRunning="{Binding IsBusy}"  
       HeightRequest="30"  
       HorizontalOptions="Center"  
       VerticalOptions="Center"  
       WidthRequest="30"/>

Tutorial: https://learn.microsoft.com/en-us/xamarin/xamarin-forms/user-interface/collectionview/populate-data#load-data-incrementally

Stesvis 1,041 Reputation points

2021-02-20T05:47:55.497+00:00

Thanks for the reply, however the threshold is reached and the command is fired only when you scroll DOWN.
I need it to fire when you scroll UP.

Is it not possible to achieve this with the CollectionView?
https://help.syncfusion.com/xamarin/listview/loadmore

1 answer

Your answer

JarvanZhang 23,971 Reputation points

2021-02-20T05:03:21.967+00:00

The CollectionView class provides the RemainingItemsThreshold and RemainingItemsThresholdReachedCommand properties which could used to load the data incrementally.

<CollectionView ItemsSource="{Binding DataCollection}" RemainingItemsThreshold="0" RemainingItemsThresholdReachedCommand="{Binding ItemTresholdReachedCommand}"> <CollectionView.ItemTemplate> <DataTemplate> ... </DataTemplate> </CollectionView.ItemTemplate> </CollectionView> <ActivityIndicator IsRunning="{Binding IsBusy}" HeightRequest="30" HorizontalOptions="Center" VerticalOptions="Center" WidthRequest="30"/>

Tutorial: https://learn.microsoft.com/en-us/xamarin/xamarin-forms/user-interface/collectionview/populate-data#load-data-incrementally
Stesvis 1,041 Reputation points

2021-02-20T05:47:55.497+00:00

Thanks for the reply, however the threshold is reached and the command is fired only when you scroll DOWN.
I need it to fire when you scroll UP.

Is it not possible to achieve this with the CollectionView?
https://help.syncfusion.com/xamarin/listview/loadmore

Answer 1

Hello,

Welcome to our Microsoft Q&A platform!

CollectionView load more when scrolling up

Try using RefreshView to wrap the CollectionView. RefreshView provides pull to refresh functionality for scrollable content.

   <RefreshView Command="{Binding RefreshItemsCommand}" IsRefreshing="{Binding IsRefreshing}">  
         
       <CollectionView ...>   
           ...  
       </CollectionView>  
   </RefreshView>

Tutorial: https://learn.microsoft.com/en-us/xamarin/xamarin-forms/user-interface/refreshview

Best Regards,

Jarvan Zhang

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CollectionView load more when scrolling up

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