c# – Xamarin将命令传递给命令参数命令

2019年7月20日 354次阅读

我刚开始使用Xamarin表单现在我有一个项目列表,我在自定义模板中显示.

我想要的行为是事件在页面上下文中触发(使用Corcav.Behaviors),但我想将单击的项目传递给命令.我似乎无法让最后一部分工作.使用下面的实现,事件正确触发,但传递的参数是MyEventsListModel,但我想要点击的项目.

注意我最好是想在xaml / viewmodel中使用一个解决方案,而不是在代码隐藏中.并且两个事件在事件上发生的替代解决方案也很好.

XAML：

<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             xmlns:behaviors="clr-namespace:Corcav.Behaviors;assembly=Corcav.Behaviors"
             x:Class="TheEventsApp.Mobile.MyEventsList"
             Title="My Events"
             x:Name="MainPage">
    <ListView ItemsSource="{Binding Events}">
        <behaviors:Interaction.Behaviors>
            <behaviors:BehaviorCollection>
                <behaviors:EventToCommand EventName="ItemTapped" Command="{Binding NavigateToEventDetails}" CommandParameter="{Binding .}" />
            </behaviors:BehaviorCollection>
        </behaviors:Interaction.Behaviors>
        <ListView.ItemTemplate>
            <DataTemplate>
                <ViewCell>
                    <StackLayout Orientation="Vertical">
                        <Label Text="{Binding Name}" />
                    </StackLayout>
                </ViewCell>
            </DataTemplate>
        </ListView.ItemTemplate>
    </ListView>
</ContentPage>

视图模型：

 [ImplementPropertyChanged]
 public class MyEventsListModel : FreshBasePageModel
 { 
    private readonly EventsDatastore eventsStore;

    public MyEventsListModel(EventsDatastore eventsStore)
    {
        this.eventsStore = eventsStore;
    }

    protected async override void ViewIsAppearing(object sender, EventArgs e)
    {
        this.Events = await eventsStore.GetMyEventsAsync();
    }

    public ObservableCollection<Event> Events { get; set; } = new ObservableCollection<Event>();

    public Command NavigateToEventDetails
    {
        get
        {
            return new Command(async (clickedEvent) =>
            {
                await CoreMethods.PushPageModel<EventDetailsPageModel>(clickedEvent);
            });
        }
    }
}

最佳答案 解决方案非常简单.在深入了解Corcav的源代码后,很容易弄明白.以下代码在
EventToCommand.cs中

private void OnFired(EventArgs e)
{
    object param = this.PassEventArgument ? e : this.CommandParameter;

    if (!string.IsNullOrEmpty(this.CommandName))
    {
        if (this.Command == null) this.CreateRelativeBinding();
    }

    if (this.Command == null) throw new InvalidOperationException("No command available, Is Command properly set up?");

    if (e == null && this.CommandParameter == null) throw new InvalidOperationException("You need a CommandParameter");

    if (this.Command != null && this.Command.CanExecute(param))
    {
        this.Command.Execute(param);
    }
}

处理它.简单地将“PassEventArgument”设置为true可以解决我的问题.

<behaviors:EventToCommand EventName="ItemTapped" Command="{Binding NavigateToEventDetails}" PassEventArgument="True" />
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