RadListView with List<T> items

[n/a]

Hello,

I am getting System.ArgumentNullException: Value cannot be null. on using RadListView with List<T> items.

I am using project with multiselect listview, and it is working with basic xamarin ListView, which I want to replace with telerik RadListView.

How I can correctly use RadListView instead of Listview in SelectMultipleBasePage.
ProjectMultiselectExample on github
Example of code:

public List<WrappedSelection<T>> WrappedItems = new List<WrappedSelection<T>>();
public SelectMultipleBasePage(List<T> items)
        {
            WrappedItems = items.Select(item => new WrappedSelection<T>() { Item = item, IsSelected = false }).ToList();
            ListView mainList = new ListView()
            {
                ItemsSource = WrappedItems,
                ItemTemplate = new DataTemplate(typeof(WrappedItemSelectionTemplate)),
            };

            mainList.ItemSelected += (sender, e) =>
            {
                if (e.SelectedItem == null) return;
                var o = (WrappedSelection<T>)e.SelectedItem;
                o.IsSelected = !o.IsSelected;
                ((ListView)sender).SelectedItem = null; //de-select
            };
            Content = mainList;
        }

[Nikolay Demirev]

Hello Dmitriy,

I have reviewed your project, and I have updated it in order to work with the RadListView. The changes I have applied are:

1. Replaced the ListView with RadListView
2. Updated the SelectionChanged event handler, so it works with the API of the RadListView
3. Changed the base type of WrappedItemSelectionTemplate so now it delivers from ListViewTemplateCell
4. Defined a Layout definition so the items are with almost the same size as with the ListView

You can find the modified project attached.

I hope this helps. 

Regards,
Nikolay Demirev
Progress Telerik

[n/a]

Hello Nikolay ,

[quote]2. Updated the SelectionChanged event handler, so it works with the API of the RadListView [/quote]

System.InvalidCastException: Specified cast is not valid.

Getting this expection on cell clicking.

May I also to ask you to add an example with RadListView Filtering feature in this multiselect page?

[Nikolay Demirev]

Hi Dmitriy,

Could you tell me how are you reproducing the InvalidCastException, because I have tested again the project I have sent to you, and I am able to toggle selected items one by one or using the "All" and "None" buttons?

I have modified the same project again, so it filters the selected items. Here is the required code for implementing the filtering:

This code snippet sets the filtering descriptor and provides a callback for the filtering logic
 

mainList.FilterDescriptors.Add(new DelegateFilterDescriptor { Filter = this.Filter });

And here it is the filtering logic:

private bool Filter(object arg)
{
    var item = (WrappedSelection<T>)arg;
    return !item.IsSelected;
}

I am attaching the sample project.
I hope this helps.

Regards,
Nikolay Demirev
Progress Telerik

[n/a]

Hello Nikolay,

Is it possible to filter RadListView in your example by "Name" of items?
[quote]Could you tell me how are you reproducing the InvalidCastException[/quote]
On switcher clicking it works well, but on cell click I have these exceptions:
Android: System.NullReferenceException
iOS: System.InvalidCastException
I added video with my steps here:
https://drive.google.com/open?id=12FwPM4THXn4nABWrDONidlZZcFug4onS

[Nikolay Demirev]

Hi Dimitriy,

I didn't reproduce the issue, because I was toggling only the switches. So now I have updated the SelectionChanged event handler. You can check it in the attached project. There were two issues in it. One was the wrong condition checking if there are no new selected items that were causing a NullReferenceException and the other was casting the sender to ListView instead of RadListView.

As for the filtering, you can filter by any property you want. Just modify the Filter method to return true if you want the item to be visible. In the sample project, the selected items are filtered. Here is the documentation article explaining how the filtering in the RadListView can be used.

Is there anything else I can help you with?

Regards,
Nikolay Demirev
Progress Telerik