How to handle ItemClick For Nested ListView In MVVM Pattern?

Question

Xaml code:

<Page
    x:Class="DemoTestApp.MainPage"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:DemoTestApp"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    mc:Ignorable="d"
    Background="{ThemeResource ApplicationPageBackgroundThemeBrush}"
    xmlns:vm="using:ViewModels"
    >

    <Page.DataContext>
       <vm:TestViewModel/>
   </Page.DataContext>

   <Grid Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
       <ListView Name="HeaderList" ItemsSource="{Binding Items}">
           <ListView.ItemTemplate>
               <DataTemplate>
                    <Grid>
                        <Border Background="Bisque">
                            <TextBlock Text="{Binding Name}"/>
                        </Border>
                        <ListView Name="SubItemsList">
                            <x:String>SubItem 1</x:String>
                            <x:String>SubItem 2</x:String>
                            <x:String>SubItem 3</x:String>
                        </ListView>
                    </Grid>
                </DataTemplate>
            </ListView.ItemTemplate>
        </ListView>
    </Grid>
</Page>

ViewModel Code:

using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ViewModels
{


class TestViewModel
{
    public class Item
    {
        public string Test { get; set; }
    }

    public ObservableCollection<Item> Items { get; set; }

    public TestViewModel()
    {
        Items = new ObservableCollection<Item>();

        Items.Add(new Item { Test = "Item 1" });
        Items.Add(new Item { Test = "Item 2" });
        Items.Add(new Item { Test = "Item 3" });
        Items.Add(new Item { Test = "Item 4" });
        Items.Add(new Item { Test = "Item 5" });
        Items.Add(new Item { Test = "Item 7" });
        Items.Add(new Item { Test = "Item 8" });
        Items.Add(new Item { Test = "Item 9" });
            Items.Add(new Item { Test = "Item 10" });
        Items.Add(new Item { Test = "Item 11" });
        }
    }
    }

This is a demo code to demonstrate my problem.

When I click on any item on the SubItemsList, I would like the event to be binded to a Command in the view model, how can I accomplish this?

Thanks for reading.

I have already looked at the two resources from stackoverflow, but none of them had anything that worked.

Just for the information, I am new to UWP and more of so to MVVM.

Answer 1

For nested ListView ItemClick in MVVM pattern, you could use Xaml Behaviors SDK to add ItemClick event just like the following.

<ListView Name="HeaderList"  ItemsSource="{Binding Items}" >
    <ListView.ItemTemplate>
        <DataTemplate>
            <Grid>
                <Border Background="Bisque">
                    <TextBlock Text="{Binding Test}"/>
                </Border>

                <ListView Name="SubItemsList" ItemsSource="{Binding SubItems}" 
                           IsItemClickEnabled="True" 
                           SelectedItem="{Binding SelectItme,Mode=TwoWay}" >
                    <ListView.ItemTemplate>
                        <DataTemplate>
                            <StackPanel Orientation="Vertical">
                                <TextBlock Text="{Binding }"/>
                            </StackPanel>
                        </DataTemplate>
                    </ListView.ItemTemplate>

                    <i:Interaction.Behaviors >
                        <ic:EventTriggerBehavior  EventName="ItemClick">
                            <ic:InvokeCommandAction  Command="{Binding ItemCommand}" 
                                                     CommandParameter="{Binding}" />
                        </ic:EventTriggerBehavior>
                    </i:Interaction.Behaviors>
                </ListView>
            </Grid>
        </DataTemplate>
    </ListView.ItemTemplate>
</ListView>

And you need to add SelectedItem="{Binding SelectItme,Mode=TwoWay}" that use to identify which item you have selected.

ViewModel

class TestViewModel
{
    public class Item : INotifyPropertyChanged
    {
        public event PropertyChangedEventHandler PropertyChanged;
        public void OnPropertyChanged([CallerMemberName] string propertyName = null)
        {
            this.PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }
        public string Test { get; set; }
        public ObservableCollection<string> SubItems { get; set; }

        private string _selectItme;

        public string SelectItme
        {
            get
            {
                return _selectItme;
            }
            set
            {
                _selectItme = value;
                OnPropertyChanged();
            }
        }
        public Item()
        {
            SubItems = new ObservableCollection<string>() { "zhuzhu", "heheh", "liuliu", "momo" };
        }

        public ICommand ItemCommand
        {
            get
            {
                return new CommadEventHandler<object>((item) => ItemClick(item));
            }
        }
        private void ItemClick(object item)
        {
            System.Diagnostics.Debug.WriteLine("--------------------");
        }
    }

    public ObservableCollection<Item> Items { get; set; }

    public TestViewModel()
    {
        Items = new ObservableCollection<Item>();

        Items.Add(new Item { Test = "Item 1" });
        Items.Add(new Item { Test = "Item 2" });
        Items.Add(new Item { Test = "Item 3" });
        Items.Add(new Item { Test = "Item 4" });
        Items.Add(new Item { Test = "Item 5" });
        Items.Add(new Item { Test = "Item 7" });
        Items.Add(new Item { Test = "Item 8" });
        Items.Add(new Item { Test = "Item 9" });
        Items.Add(new Item { Test = "Item 10" });
        Items.Add(new Item { Test = "Item 11" });
    }

}

class CommadEventHandler<T> : ICommand
{
    public event EventHandler CanExecuteChanged;

    public Action<T> action;
    public bool CanExecute(object parameter)
    {
        return true;
    }

    public void Execute(object parameter)
    {
        this.action((T)parameter);
    }
    public CommadEventHandler(Action<T> action)
    {
        this.action = action;

    }
}