DevExpress CollectionView Collapse Groups in Xamarin.Forms App
In this article, we'll explore how to use the DevExpress CollectionView component in Xamarin.Forms to collapse groups. We will cover the key concepts of the CollectionView and the Grouping functionality provided by the DevExpress library.
Introduction
Xamarin.Forms is a popular framework for building cross-platform mobile applications using .NET. DevExpress is a UI components library that enhances Xamarin.Forms and provides a set of advanced controls, including a powerful CollectionView control. We will use the DevExpress.XamarinForms.DataGrid package in this example.
CollectionView and Grouping
The CollectionView is a data-bound control that allows you to display lists of items in Xamarin.Forms applications. With DevExpress CollectionView, you can group items using the built-in Grouping functionality. The Grouping feature enables you to display the group header and collapsible rows.
Adding DevExpress CollectionView to Xamarin.Forms App
To get started, install the DevExpress.XamarinForms.DataGrid package using the NuGet Package Manager. Here's a sample implementation of the CollectionView in XAML:
<dxg:CollectionView.ItemsSource>
<dxg:GroupedObservableCollection
ItemsSource="{Binding Tasks}">
<dxg:Grouping
Title="{Binding Key}"
FieldName="CategoryName">
</dxg:Grouping>
</dxg:GroupedObservableCollection>
</dxg:CollectionView.ItemsSource>
In the code snippet above, we use the GroupedObservableCollection class to bind the ItemsSource property to a list of tasks grouped by their categories. The Grouping tag sets the group header title and associated field name.
Collapsing Groups
By default, DevExpress CollectionView groups are expandable and collapsible. To collapse a specific group, handle the GroupExpanded event. You can set the IsExpanded property of the group to false to collapse it. Here's a code example:
private void GroupExpanded(object sender, GroupExpandedEventArgs e)
{
foreach (var group in (sender as CollectionView).Groups)
{
if (group.Key.Equals(e.Group.Key))
{
group.IsExpanded = false;
}
}
}
In the implementation above, we attach an event handler for the GroupExpanded event. When the user expands a group, we iterate through all groups in the CollectionView and collapse the group with a matching key by setting the IsExpanded property to false.
Opening Popup Page
To open a pop-up page from the CollectionView, use the Rg.Plugins.Popups library. First, install Rg.Plugins.Popups package via NuGet. Then, create a PopupPage and use the IShowPopupRequest interface to display the pop-up page when a group header is tapped:
<dxg:CollectionView.GroupHeaderTemplate>
<DataTemplate>
<ViewCell>
<StackLayout Tapped="StackLayout_Tapped">
...
</StackLayout>
</ViewCell>
</
```less
private async void StackLayout_Tapped(object sender, System.EventArgs e)
{
var group = (sender as StackLayout).BindingContext as Group;
var popupPage = new MyPopupPage();
popupPage.Initialize(...);
await PopupNavigation.Instance.PushAsync(popupPage);
}
```
- DevExpress CollectionView is a powerful data-bound control for displaying lists of items in Xamarin.Forms. It enables grouping functionality by default, which allows you to collapse and expand groups.
- To collapse a specific CollectionView group, handle the GroupExpanded event and set the IsExpanded property of the group to false.
- To open a pop-up page from a CollectionView, use Rg.Plugins.Popups library and attach the Tapped event handler for the group header template.