I started using RadTreeView, so I added XAML reference and tree to page, and corresponding collection in viewmodel.
After add Item to collection I got exception as below:
05-22 14:54:25.831 E/mono-rt ( 4107): [ERROR] FATAL UNHANDLED EXCEPTION: System.NullReferenceException: Object reference not set to an instance of an object.
at Telerik.XamarinForms.DataControls.RadTreeView.UpdateParentItemOnAddRemove
at Telerik.XamarinForms.DataControlsRenderer.Android.TreeViewRenderer.LayoutItemAdded
at Telerik.XamarinForms.DataControls.TreeView.TreeViewLayout.RaiseLayoutItemAdded
at Telerik.XamarinForms.DataControls.TreeView.TreeViewLayout.AddItem
at Telerik.XamarinForms.DataControls.TreeView.TreeViewLayout.OnCollectionChanged
at System.Collections.ObjectModel.ObservableCollection`1[T].OnCollectionChanged4 Answers, 1 is accepted
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answered on 22 May 2018, 02:16 PM
Git source code for sample.
git clone https://brzezinol2@bitbucket.org/brzezinol2/prismteleriktest.git
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answered on 22 May 2018, 04:43 PM
I investigate more and I found hidden exception:
{System.InvalidOperationException: Iterating over item that was iterated... at Telerik.XamarinForms.DataControls.TreeView.TreeViewLayout.PopulateTable at Telerik.XamarinForms.DataControls.TreeView.TreeViewLayout.PopulateTable at Telerik.XamarinForms.DataControls.TreeView.TreeViewLayout.PopulateTable at Telerik.XamarinForms.DataControls.TreeView.TreeViewLayout.AddItem at Telerik.XamarinForms.DataControls.TreeView.TreeViewLayout.OnCollectionChanged at System.Collections.ObjectModel.ObservableCollection`1[T].OnCollectionChanged at System.Collections.ObjectModel.ObservableCollection`1[T].OnCollectionChanged at System.Collections.ObjectModel.ObservableCollection`1[T].InsertItem at System.Collections.ObjectModel.Collection`1[T].Add (T item) at PrismTelerikTest.ViewModels.TelerikTreeViewPageViewModel.OnNavigatingTo 0
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answered on 22 May 2018, 06:01 PM
I just find out what was wrong,
TreeView need to create nested ViewModel containing items source collection.
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Hello Maciej,
I'm glad you were able to find a solution. You're correct, there should be an item adapter that tells the TreeView where to get the nested items, which are typically located within the same model definition. Take a look at the Getting Started Example for more guidance.
Regards,
Lance | Tech Support Engineer, Sr.
Progress Telerik
I'm glad you were able to find a solution. You're correct, there should be an item adapter that tells the TreeView where to get the nested items, which are typically located within the same model definition. Take a look at the Getting Started Example for more guidance.
Regards,
Lance | Tech Support Engineer, Sr.
Progress Telerik
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