xamarin-forms-docs/knowledge-base/treeview-official-release-changes.md

title	description	type	page_title	slug	position	tags	ticketid	res_type
How to upgrade TreeView from Beta to Official	TreeView official release introduces API changes	how-to	TreeView official release changes	treeview-official-release-changes		treeview, changes, upgrade, IHierarchyAdapter, interface, adapter, how-to, Beta, official, release, API, Xamarin, XamarinForms		kb

Environment

Product Version	R3 2018
Product	TreeView for Xamarin

Description

What changes are introduced with the official release of RadTreeView for Xamarin and how to upgrade from Beta to Official?

Solution

With its official release in R3 2018 RadTreeView introduces a few API changes described below.

IHierarchyAdapter interface is replaced with TreeViewDescriptors

We reconsidered items loading mechanism in order to enable XAML-only setup of RadTreeView. Now, the IHierarchyAdapter interface is replaced with TreeViewDescriptors. To illustrate the new API, we’ll check the following example:

Let’s have “Item” business object that holds its subitems in Children collection:

public class Item 
{
    public string Name { get; set; }
    public IList<Item> Children {get; set;}
}

We'll use a collection of Item objects as an ItemsSource of RadTreeListView. The approach for defining the hieararchy has changed like this:

Previously:

Create a custom HierarchyAdapter class which implements IHierarchyAdapter:

public class TreeViewDemoAdapter : IHierarchyAdapter
{
    public object GetItemAt(object item, int index)
    {
        return (item as Item).Children[index];
    }

    public IEnumerable<object> GetItems(object item)
    {
        return (item as Item).Children ?? Enumerable.Empty<object>();
    }
} 

And set it to the RadTreeView HierarchyAdapter property:

treeView.HierarchyAdapter = new TreeViewDemoAdapter();

Now with R3 2018:

Apply TreeViewDescriptor to RadTreeView with the corresponding properties (DisplayMemberPath and ItemsSourcePath) applied:

<telerikDataControls:RadTreeView x:Name="treeView" ItemsSource="{Binding Source}">
     <treeView:TreeViewDescriptor DisplayMemberPath="Name"
								 ItemsSourcePath="Children"
								 TargetType="{x:Type local:Item}"/>
</telerikDataControls:RadTreeView>

ItemActionEventsArgs is replaced with TreeViewItemEventArgs

This change is made in order to unify the events arguments related to the TreeView control.

Let’s for example subscribe to ItemTapped event of RadTreeView:

<telerikDataControls:RadTreeView x:Name="treeView" 
							 ItemsSource="{Binding Source}" 
							 ItemTapped="treeView_ItemTapped" />

Previously:

private void treeView_ItemTapped(object sender, Telerik.XamarinForms.DataControls.TreeView.ItemActionEventArgs e)
{
	var tappedItem = e.Item;
}

Now with R3 2018:

private void tv_ItemTapped(object sender, Telerik.XamarinForms.DataControls.TreeView.TreeViewItemEventArgs e)
{
	var tappedItem = e.Item;
}