如何将数据(ListView的selectItem)从xaml发送到ViewModel [英] How send data (selectItem of listView) from xaml to ViewModel

问题描述

我想在我的viewModel中选择数据

I want get data selected in my viewModel

这是我的xaml，但是我不知道如何解决我的xaml，因为这很不好，如何在我的xaml中使用我的行为?

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">

在我的邮政编码

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);
            }

但是我想进入我的viewModel，不要进入我的背后代码

but i want to get in my viewModel, dont in my behind code

我见过要解决的是命令或行为

i've seen to solved is with commands, or behaviors

这是我的viewModel:

this is my viewModel:

public class ActorsViewModel : ViewModelBase
    {
        public List<Actor> actors { get; set; }

        public AccountsViewModel(IActorManager actorManager)
            : base()
        {

编辑，我正在使用命令，但我不知道如何使用John Livermore的答案，我想使用并显示控制台Console.WriteLine("ROW");.

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");
                });
            }
        }
    }

推荐答案

由于您要求的ListView选择行为更加简单.请使用以下内容:

Since you had asked for a simpler Behavior for ListView selection changed. Please use the following:

以下类继承自

Following class is inherited from BehaviorBase which takes care of BindingContext allocation.

1. 在OnAttachedTo覆盖上，钩住了ItemSelected事件.
2. 在OnDetachingFrom覆盖上，未解除ItemSelected事件的锁定.
3. Command可绑定属性绑定到ViewModel
中的Command
4. 在e.SelectedItem传递给命令的情况下. (改变 它等于您希望传递的任何值)

1. On the OnAttachedTo override the ItemSelected event is hooked.
2. On the OnDetachingFrom override the ItemSelected event is unhooked.
3. Command bindable property Binds to the Command in ViewModel
4. 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);
        }
    }
}

用法

Xaml

<ListView ItemsSource="{Binding Collection}">
            <ListView.Behaviors>
                <local:SelectionChangedEventBehavior Command="{Binding SelectionCommand}" />
            </ListView.Behaviors>
        </ListView>

ViewModel

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);
    }
}

希望这对您可能有用.如果可能，请使用 EventToCommandBehavior ，因为您可以将其重用于任何控件和任何事件.

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.

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