How send data (selectItem of listView) from xaml to ViewModel - xamarin.forms

Question

I want get data selected in my viewModel
this is my xaml, but i donot know how solved my xaml, because this is bad, how use my behavior here in my xaml?
<ListView.Behaviors>
<behaviors:ItemTappedBehavior EventName="ItemSelected">
<behaviors:InvokeCommandAction Command="{Binding SelectedTagChanged}" />
</behaviors:ItemTappedBehavior>
</ListView.Behaviors>
<ListView ItemsSource="{Binding actors}" ItemTapped="ListView_ItemTapped">
in my behindcode
public partial class ActorsView : ContentPage
{
public AccountsView()
{
InitializeComponent();
}
async void ListView_ItemTapped(object sender, ItemTappedEventArgs e)
{
Actor selectedItem = (Actor)e.Item;
Console.WriteLine("WORK"+ Actor.Name);
}
but i want to get in my viewModel, dont in my behind code
i've seen to solved is with commands, or behaviors
this is my viewModel:
public class ActorsViewModel : ViewModelBase
{
public List<Actor> actors { get; set; }
public AccountsViewModel(IActorManager actorManager)
: base()
{
Edit, i am using commands but i dont know how use the answer from John Livermore, i want to use and show the console Console.WriteLine("ROW");.
public class ItemTappedBehavior : Behavior<ListView>
{
public ICommand Command { get; set; }
protected override void OnAttachedTo(ListView bindable)
{
base.OnAttachedTo(bindable);
}
protected override void OnDetachingFrom(ListView bindable)
{
base.OnDetachingFrom(bindable);
}
public Command SelectedTagChanged
{
get
{
return new Command(row =>
{
Console.WriteLine("ROW");
});
}
}
}

Answer 1

Since you had asked for a simpler Behavior for ListView selection changed. Please use the following:
Following class is inherited from BehaviorBase which takes care of BindingContext allocation.
On the OnAttachedTo override the ItemSelected event is hooked.
On the OnDetachingFrom override the ItemSelected event is unhooked.
Command bindable property Binds to the Command in ViewModel
In the event the e.SelectedItem is passed to the Command. (Change
it to whatever value you wish to pass)
public class SelectionChangedEventBehavior : BehaviorBase<ListView>
{
public static readonly BindableProperty CommandProperty = BindableProperty.Create("Command", typeof(ICommand), typeof(SelectionChangedEventBehavior), null);
public ICommand Command
{
get { return (ICommand)GetValue(CommandProperty); }
set { SetValue(CommandProperty, value); }
}
protected override void OnAttachedTo(BindableObject bindable)
{
base.OnAttachedTo(bindable);
AssociatedObject.ItemSelected += AssociatedObject_ItemSelected;
}
protected override void OnDetachingFrom(ListView bindable)
{
base.OnDetachingFrom(bindable);
AssociatedObject.ItemSelected -= AssociatedObject_ItemSelected;
}
private void AssociatedObject_ItemSelected(object sender, SelectedItemChangedEventArgs e)
{
if (Command != null)
{
Command.Execute(e.SelectedItem);
}
}
}
Usage
Xaml
<ListView ItemsSource="{Binding Collection}">
<ListView.Behaviors>
<local:SelectionChangedEventBehavior Command="{Binding SelectionCommand}" />
</ListView.Behaviors>
</ListView>
ViewModel
public class ViewModel : INotifyPropertyChanged
{
public Command<object> SelectionCommand { get; set; }
public ViewModel()
{
SelectionCommand = new Command<object>(OnSelection);
}
private void OnSelection(object item)
{
var selectedActor = (item as Actor);
}
}
Hope this could be useful for you. If possible use the EventToCommandBehavior as whole, just because you can reuse it for any control and any event.

Answer 2

In your XAML do the following:
Set your <ListView ItemsSource="{Binding actors}" ItemTapped="ListView_ItemTapped">
to be <ListView ItemsSource="{Binding actors}" SelectedItem = "{Binding SelectedActor, Mode=TwoWay}>
In your view model which your current XAML is bound to, create two new variables as so:
private Actor selectedActor;
public Actor SelectedActor {
get {return selectedActor;}
set {
selectedActor = value;
if(selectedActor != null) {//set properties here if needed}
OnPropertyChanged("SelectedActor"); //or however you raise your events, this is a
//custom method i've made
}
Now, where we define our actors item source, we will also define what a selectedActor is as so:
//get your actors, loop over them and add them to the list of actors
var actorItem = new Actor();
actors.Add(actorItem);
//outside of list raise the property changed event on your actors list.
OnPropertyChanged("actors")
That is a the pattern that i've used at work to get my selected item. If you then need to do something with it you could define it within the SelectedActor variable. For us our app is a hybrid between old xamarin (.Android and .iOS) and .Forms, so we pass Actions from the native level to the view model (ex: loading the summary page for the selected item)