How to bind a ListView.ItemTapped event to a ViewModel command in Xamarin Forms?

Question

I'm using Prism to implement MVVM.

And I have a situation where I have a ListView and have to handle the ItemTapped event and also get the tapped item.

I tried using EventToCommandBehavior.

But I couldn't get it to work cause it was not recognising the references that were added.

Answer 1

The EventToCommandBehavior does not currently exist in the pre1 package available on NuGet. This should be available when pre2 is released.

My recommendation would be that you either copy the EventToCommandBehavior to your project for now, or you could add one that I use:

/// <summary>
/// ListView Item Tapped Behavior.
/// </summary>
public class ItemTappedBehavior : BehaviorBase<ListView>
{
    /// <summary>
    /// Gets or sets the command.
    /// </summary>
    /// <value>The command.</value>
    public ICommand Command { get; set; }

    /// <inheritDoc />
    protected override void OnAttachedTo( ListView bindable )
    {
        base.OnAttachedTo( bindable );
        AssociatedObject.ItemTapped += OnItemTapped;
    }

    /// <inheritDoc />
    protected override void OnDetachingFrom( ListView bindable )
    {
        base.OnDetachingFrom( bindable );
        AssociatedObject.ItemTapped -= OnItemTapped;
    }

    void OnItemTapped( object sender, ItemTappedEventArgs e )
    {
        if ( Command == null || e.Item == null ) return;

        if ( Command.CanExecute( e.Item ) )
            Command.Execute( e.Item );
    }
}

Then in your Xaml

<ListView.Behaviors>
    <behaviors:ItemTappedBehavior Command="{Binding SelectedItemCommand}" />
</ListView.Behaviors>

Answer 2

I would suggest a different approach.

public class AppListView: ListView{

    public AppListView(): base(ListViewCachingStrategy.RecycleElement){
        this.ItemSelected += (s,e)=>{
            this.TapCommand?.Invoke(e.Item);
        }
    }

    #region Property TapCommand

    /// <summary>
    /// Bindable Property TapCommand
    /// </summary>
    public static readonly BindableProperty TapCommandProperty = BindableProperty.Create(
      nameof(TapCommand),
      typeof(System.Windows.Input.ICommand),
      typeof(AppListView),
      null,
      BindingMode.OneWay,
      null,
      null,
      null,
      null,
      null
    );

    /// <summary>
    /// Property TapCommand
    /// </summary>
    public System.Windows.Input.ICommand TapCommand
    {
        get
        {
            return (System.Windows.Input.ICommand)GetValue(TapCommandProperty);
        }
        set
        {
            SetValue(TapCommandProperty, value);
        }
    }
    #endregion

}

Now use AppListView instead of ListView and use TapCommand="{Binding ...}". In order for intellisense to work correctly, I suggest keep this class in a separate library project (one for android, one for iOS and keep this file in shared project between all library projects).