therealjohn/IncrementalListView

Incremental ListView Control and Plugin for Xamarin.Forms

IncremementalListView Plugin for Xamarin.Forms

IncrementalListView Plugin for Xamarin.Forms which provides an IncrementalListView control for loading data incrementally as a user scrolls.

Where to get it?

You can clone or download the repo and build it yourself. Or, grab it from Nuget.

How to Use

To get started, add a reference to the IncrementalListView.FormsPlugin.dll in your PCL project (directly or using NuGet). The plugin is a single PCL and it's not required for every platform project unless using a Shared Assets Project type.

Next, implement the ISupportIncrementalLoading interface on your ViewModel that will be the BindingContext of the IncrementalListViewControl. Here is an example:

public class IncrementalViewModel : INotifyPropertyChanged, ISupportIncrementalLoading
{
    public int PageSize { get; set; } = 20;

    public ICommand LoadMoreItemsCommand { get; set; }

    public bool IsLoadingIncrementally { get; set; } 

    public bool HasMoreItems { get; set; }

    public IncrementalViewModel()
    {
        LoadMoreItemsCommand = new Command(async () => await LoadMoreItems());
    }

    async Task LoadMoreItems()
    {
        IsLoadingIncrementally = true;

        // Download data from a service, etc.
        // Add the newly download data to a collection

        HasMoreItems = ...

        IsLoadingIncrementally = false;
    }
}

Then, add a namespace in your XAML page for the plugin:

xmlns:plugin="clr-namespace:IncrementalListView.FormsPlugin;assembly=IncrementalListView.FormsPlugin"

Now, Add the control to a ContentPage:

<local:IncrementalListView
    ItemsSource="{Binding MyItems}"
    PreloadCount="5">

    <x:Arguments>
        <ListViewCachingStrategy>RecycleElement</ListViewCachingStrategy>
    </x:Arguments>

    <ListView.ItemTemplate>
        ...      
    </ListView.ItemTemplate>
    <ListView.Footer>
        <ActivityIndicator Margin="20" IsRunning="{Binding IsLoadingIncrementally}" IsVisible="{Binding IsLoadingIncrementally}"/>        
    </ListView.Footer>
</local:IncrementalListView>

Finally, customize the PreloadCount property for how close to the bottom of the list the user has to get to before a load is started. A value of 0 means the user has to reach the end of the list. In this example, the user would reach the n - 5, where n is MyItems.Count.

Feedback

Let me know if you have suggestions or feedback on this control!

License

See the LICENSE file.