Xamarin Forms Switch Toggled event not associated with viewmodel

Question

I have a Forms XAML page, and there I have a listview, and each element has a Switch (xamarin default). I can bind the data from the elements to the list, but I can not prompt the Switch "Toggled" event, since this does not allow the element to be shown. I also tried with ICommand and Command, as it is instructed to do with buttons, but the result is the same, nothing is displayed. How can I switch a switch from my view model?

View

    <?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             x:Class="TouristicWallet.Views.WalletManagementPage"
             xmlns:vm="clr-namespace:TouristicWallet.ViewModels"
             xmlns:converters="clr-namespace:TouristicWallet.Converters"
             >

  <ContentPage.BindingContext>
    <vm:WalletManagementViewModel x:Name="ViewModel"/>
  </ContentPage.BindingContext>

  <ContentPage.Resources>
    <ResourceDictionary>
      <converters:CurrencyIdToCodeConverter x:Key="idToCodeConverter"/>
    </ResourceDictionary>
  </ContentPage.Resources>

  <StackLayout>
    <ListView x:Name="MyCurrencies" ItemsSource="{Binding Currencies, Mode=OneWay}">
      <ListView.ItemTemplate>
        <DataTemplate>
          <ViewCell>
            <StackLayout Orientation="Horizontal">
              <Label Text="{Binding Currency.Initials, Mode=OneWay}" />
              <Switch IsToggled="{Binding IsOwned, Mode=TwoWay}"
                      Toggled="{Binding Toggled}"
                      />
            </StackLayout>
          </ViewCell>
        </DataTemplate>
      </ListView.ItemTemplate>
    </ListView>

  </StackLayout>
</ContentPage>

ViewModel

public class WalletManagementViewModel : ViewModelBase
{

    private readonly List<OwnedCurrencyWrapper> _currencies = new List<OwnedCurrencyWrapper>();
    public List<OwnedCurrencyWrapper> Currencies { get { return _currencies; } }

    public WalletManagementViewModel()
    {
        CurrencyDataAccess cda = new CurrencyDataAccess();
        foreach (var item in cda.GetCurrencies())
        {
            Currencies.Add(new OwnedCurrencyWrapper(item));
        }

        OnPropertyChanged(nameof(Currencies));
    }

    public class OwnedCurrencyWrapper
    {
        public Currency Currency { get; private set; }
        public Boolean IsOwned { get; set; }
        public ICommand Toggled { get; set; }


        public OwnedCurrencyWrapper(Currency currency)
        {
            Currency = currency;
            WalletDataAccess wda = WalletDataAccess.Instance;
            IsOwned = wda.IsOwned(Currency.Id);

            Toggled = new Command(() => Update());
        }

        public void Update()
        {
            WalletDataAccess wda = WalletDataAccess.Instance;
            if (IsOwned) wda.RemoveOwnedCurrency(Currency.Id);
            else wda.OwnCurrency(Currency.Id);

        }

        public void Toggled_handler(object sender, ToggledEventArgs e)
        {
            Update();
        }
    }
}

I do not use mvvm framework

Answer 1

Command. : https://developer.xamarin.com/guides/xamarin-forms/xaml/xaml-basics/data_bindings_to_mvvm/#Commanding_with_ViewModels

, Forms, ICommand:

• MenuItem
• SearchBar
• TextCell (, , ImageCell)
• ListView
• TapGestureRecognizer

" ", XAML:

<Switch IsToggled="{Binding IsOwned, Mode=TwoWay}"
        Toggled="Handle_Toggled" />

:

void Handle_Toggled(object sender, Xamarin.Forms.ToggledEventArgs e)
{
    // Do stuff
}

, , OwnedCurrencyWrapper (, , ), IsOwned. Toggled ::

<Switch IsToggled="{Binding IsOwned, Mode=TwoWay}" />

OwnedCurrencyWrapper:

bool _isOwned;
public bool IsOwned { 
    get 
    {
        return _isOwned;
    } 
    set
    {
        _isOwned = value;
        // Do any other stuff you want here
    }
}

, , INotifyPropertyChanged, , , . Forms MVVM . https://developer.xamarin.com/guides/xamarin-forms/xaml/xaml-basics/data_bindings_to_mvvm/

: Xamarin Forms. : https://github.com/xamarin/xamarin-forms-samples/tree/master/Behaviors/EventToCommandBehavior

- . , , . .

, Toggled .

Answer 2

, Toggled eventHandler, . .

<Switch IsToggled="{Binding SwitchEnabled}"  x:Name="MySwitch">
    <Switch.Behaviors>
    <!-- behaviors namespace comes from Xamarin.Forms behaviors nuget  -->
        <behaviors:EventHandlerBehavior EventName="Toggled">
            <behaviors:InvokeCommandAction Command="{Binding ToggleSwitchCommand}" />
        </behaviors:EventHandlerBehavior>
    </Switch.Behaviors>
</Switch>

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