Display an EmptyView when Data is Unavailable

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Important

The CollectionView is currently a preview, and lacks some of its planned functionality. In addition, the API may change as the implementation is completed.

CollectionView defines the following properties that can be used to provide user feedback when there's no data to display:

  • EmptyView, of type object, the string, binding, or view that will be displayed when the ItemsSource property is null, or when the collection specified by the ItemsSource property is null or empty. The default value is null.
  • EmptyViewTemplate, of type DataTemplate, the template to use to format the specified EmptyView. The default value is null.

These properties are backed by BindableProperty objects, which means that the properties can be targets of data bindings.

The main usage scenarios for setting the EmptyView property are displaying user feedback when a filtering operation on a CollectionView yields no data, and displaying user feedback while data is being retrieved from a web service.

Note

The EmptyView property can be set to a view that includes interactive content if required.

For more information about data templates, see Xamarin.Forms Data Templates.

Display a string when data is unavailable

The EmptyView property can be set to a string, which will be displayed when the ItemsSource property is null, or when the collection specified by the ItemsSource property is null or empty. The following XAML shows an example of this scenario:

<CollectionView ItemsSource="{Binding EmptyMonkeys}"
                EmptyView="No items to display" />

The equivalent C# code is:

CollectionView collectionView = new CollectionView
{
    EmptyView = "No items to display"
};
collectionView.SetBinding(ItemsView.ItemsSourceProperty, "EmptyMonkeys");

The result is that, because the data bound collection is null, the string set as the EmptyView property value is displayed:

Screenshot of a CollectionView vertical list with a text empty view, on iOS and Android

Display views when data is unavailable

The EmptyView property can be set to a view, which will be displayed when the ItemsSource property is null, or when the collection specified by the ItemsSource property is null or empty. This can be a single view, or a view that contains multiple child views. The following XAML example shows the EmptyView property set to a view that contains multiple child views:

<StackLayout Margin="20">
    <SearchBar x:Name="searchBar"
               SearchCommand="{Binding FilterCommand}"
               SearchCommandParameter="{Binding Source={x:Reference searchBar}, Path=Text}"
               Placeholder="Filter" />
    <CollectionView ItemsSource="{Binding Monkeys}">
        <CollectionView.ItemTemplate>
            <DataTemplate>
                ...
            </DataTemplate>
        </CollectionView.ItemTemplate>
        <CollectionView.EmptyView>
            <StackLayout>
                <Label Text="No results matched your filter."
                       Margin="10,25,10,10"
                       FontAttributes="Bold"
                       FontSize="18"
                       HorizontalOptions="Fill"
                       HorizontalTextAlignment="Center" />
                <Label Text="Try a broader filter?"
                       FontAttributes="Italic"
                       FontSize="12"
                       HorizontalOptions="Fill"
                       HorizontalTextAlignment="Center" />
            </StackLayout>
        </CollectionView.EmptyView>
    </CollectionView>
</StackLayout>

The equivalent C# code is:

SearchBar searchBar = new SearchBar { ... };
CollectionView collectionView = new CollectionView
{
    EmptyView = new StackLayout
    {
        Children =
        {
            new Label { Text = "No results matched your filter.", ... },
            new Label { Text = "Try a broader filter?", ... }
        }
    }
};
collectionView.SetBinding(ItemsView.ItemsSourceProperty, "Monkeys");

When the SearchBar executes the FilterCommand, the collection displayed by the CollectionView is filtered for the search term stored in the SearchBar.Text property. If the filtering operation yields no data, the StackLayout set as the EmptyView property value is displayed:

Screenshot of a CollectionView vertical list with custom empty view, on iOS and Android

Display a templated custom type when data is unavailable

The EmptyView property can be set to a custom type, whose template is displayed when the ItemsSource property is null, or when the collection specified by the ItemsSource property is null or empty. The EmptyViewTemplate property can be set to a DataTemplate that defines the appearance of the EmptyView. The following XAML shows an example of this scenario:

<StackLayout Margin="20">
    <SearchBar x:Name="searchBar"
               SearchCommand="{Binding FilterCommand}"
               SearchCommandParameter="{Binding Source={x:Reference searchBar}, Path=Text}"
               Placeholder="Filter" />
    <CollectionView ItemsSource="{Binding Monkeys}">
        <CollectionView.ItemTemplate>
            <DataTemplate>
                ...
            </DataTemplate>
        </CollectionView.ItemTemplate>
        <CollectionView.EmptyView>
            <views:FilterData Filter="{Binding Source={x:Reference searchBar}, Path=Text}" />
        </CollectionView.EmptyView>
        <CollectionView.EmptyViewTemplate>
            <DataTemplate>
                <Label Text="{Binding Filter, StringFormat='Your filter term of {0} did not match any records.'}"
                       Margin="10,25,10,10"
                       FontAttributes="Bold"
                       FontSize="18"
                       HorizontalOptions="Fill"
                       HorizontalTextAlignment="Center" />
            </DataTemplate>
        </CollectionView.EmptyViewTemplate>
    </CollectionView>
</StackLayout>

The equivalent C# code is:

SearchBar searchBar = new SearchBar { ... };
CollectionView collectionView = new CollectionView
{
    EmptyView = new FilterData { Filter = searchBar.Text },
    EmptyViewTemplate = new DataTemplate(() =>
    {
        return new Label { ... };
    })
};

The FilterData type defines a Filter property, and a corresponding BindableProperty:

public class FilterData : BindableObject
{
    public static readonly BindableProperty FilterProperty = BindableProperty.Create(nameof(Filter), typeof(string), typeof(FilterData), null);

    public string Filter
    {
        get { return (string)GetValue(FilterProperty); }
        set { SetValue(FilterProperty, value); }
    }
}

The EmptyView property is set to a FilterData object, and the Filter property data binds to the SearchBar.Text property. When the SearchBar executes the FilterCommand, the collection displayed by the CollectionView is filtered for the search term stored in the Filter property. If the filtering operation yields no data, the Label defined in the DataTemplate, that's set as the EmptyViewTemplate property value, is displayed:

Screenshot of a CollectionView vertical list with an empty view template, on iOS and Android

Note

When displaying a templated custom type when data is unavailable, the EmptyViewTemplate property can be set to a view that contains multiple child views.

Choose an EmptyView at runtime

Views that will be displayed as an EmptyView when data is unavailable, can be defined as ContentView objects in a ResourceDictionary. The EmptyView property can then be set to a specific ContentView, based on some business logic, at runtime. The following XAML example shows an example of this scenario:

<?xml version="1.0" encoding="UTF-8"?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             x:Class="CollectionViewDemos.Views.EmptyViewSwapPage"
             Title="EmptyView (swap)">
    <ContentPage.Resources>
        <ContentView x:Key="BasicEmptyView">
            <StackLayout>
                <Label Text="No items to display."
                       Margin="10,25,10,10"
                       FontAttributes="Bold"
                       FontSize="18"
                       HorizontalOptions="Fill"
                       HorizontalTextAlignment="Center" />
            </StackLayout>
        </ContentView>
        <ContentView x:Key="AdvancedEmptyView">
            <StackLayout>
                <Label Text="No results matched your filter."
                       Margin="10,25,10,10"
                       FontAttributes="Bold"
                       FontSize="18"
                       HorizontalOptions="Fill"
                       HorizontalTextAlignment="Center" />
                <Label Text="Try a broader filter?"
                       FontAttributes="Italic"
                       FontSize="12"
                       HorizontalOptions="Fill"
                       HorizontalTextAlignment="Center" />
            </StackLayout>
        </ContentView>
    </ContentPage.Resources>

    <StackLayout Margin="20">
        <SearchBar x:Name="searchBar"
                   SearchCommand="{Binding FilterCommand}"
                   SearchCommandParameter="{Binding Source={x:Reference searchBar}, Path=Text}"
                   Placeholder="Filter" />
        <StackLayout Orientation="Horizontal">
            <Label Text="Toggle EmptyViews" />
            <Switch Toggled="OnEmptyViewSwitchToggled" />
        </StackLayout>
        <CollectionView x:Name="collectionView"
                        ItemsSource="{Binding Monkeys}">
            <CollectionView.ItemTemplate>
                <DataTemplate>
                    ...
                </DataTemplate>
            </CollectionView.ItemTemplate>
        </CollectionView>
    </StackLayout>
</ContentPage>

This XAML defines two ContentView objects in the page-level ResourceDictionary, with the Switch object controlling which ContentView object will be set as the EmptyView property value. When the Switch is toggled, the OnEmptyViewSwitchToggled event handler executes the ToggleEmptyView method:

void ToggleEmptyView(bool isToggled)
{
    collectionView.EmptyView = isToggled ? Resources["BasicEmptyView"] : Resources["AdvancedEmptyView"];
}

The ToggleEmptyView method sets the EmptyView property of the collectionView object to one of the two ContentView objects stored in the ResourceDictionary, based on the value of the Switch.IsToggled property. When the SearchBar executes the FilterCommand, the collection displayed by the CollectionView is filtered for the search term stored in the SearchBar.Text property. If the filtering operation yields no data, the ContentView object set as the EmptyView property is displayed:

Screenshot of a CollectionView vertical list with swapped empty views, on iOS and Android

For more information about resource dictionaries, see Xamarin.Forms Resource Dictionaries.