ListView自定义ViewCell中带有Tap GestureRecognizer的标签不起作用

Question

我有一个带有自定义ViewCell的列表视图，该列表具有一个Label和一个TapGestureRecognizer，我想在 Parent BindingContext中触发它。该视图单元绑定到“ Something”视图模型，SomeThing视图模型是SomethingBigger视图模型的一部分。

public class CustomViewCell : ViewCell 
{

    #region bindable properties

    public static readonly BindableProperty ToggleCommandProperty =
        BindableProperty.Create(nameof(ToggleCommand), typeof(Command), typeof(CustomViewCell), null);

    public ICommand ToggleCommand
    {
        get { return (ICommand)GetValue(ToggleCommandProperty); }
        set { SetValue(ToggleProperty, value); }
    }

    #endregion


    public CustomViewCell
    {
        Grid grid = new Grid
        {
            ColumnSpacing = 3,
            RowSpacing = 0
        };

        //..........
        // adding other elements here
        //..........

        var addLabel = new Label
        {
            Text = "+ Add",
            FontSize = 11,
            WidthRequest = 40,
            Margin = new Thickness(0, 0, 0, 5),
            HorizontalOptions = LayoutOptions.FillAndExpand,
            VerticalOptions = LayoutOptions.FillAndExpand,
            VerticalTextAlignment = TextAlignment.Center,
            HorizontalTextAlignment = TextAlignment.Center
        };

        addLabel.GestureRecognizers.Add(new TapGestureRecognizer
        {
            Command = ToggleCommand,
            CommandParameter = BindingContext
        });

        grid.Children.Add(addLabel, 7, 1);
        Grid.SetRowSpan(addLabel, 2);

        View = grid;
    }
}

SomethingBiggerViewModel，其中包含在点击标签时应执行的命令：

public class SomethingBiggerViewModel 
{
     public ICommand ToggleCommand { get; set; }

     public SomethingBiggerViewModel() 
     {
          ToggleCommand = new Command<SomethingViewModel>(async (something) => await ExecuteToggleCommand(something));
     }

    async Task ExecuteToggleCommand(SomethingViewModel something)
    {
        await _pageService.DisplayAlert("title", "item clicked " + something.Name, "Cancel");
    }
}

并在页面中：

<ListView Grid.Row="3" 
            VerticalOptions="FillAndExpand"
            CachingStrategy="RecycleElement"
            x:Name="linesListView" 
            RowHeight="{Binding LineRowHeight}"
            ItemsSource="{Binding Lines}"
            SeparatorColor="#bfbfbf">
    <ListView.ItemTemplate>
        <DataTemplate>
            <views:CustomViewCell ToggleCommand="{Binding Source={x:Reference ThePage}, Path=BindingContext.ToggleCommand}" />
        </DataTemplate>
    </ListView.ItemTemplate>
</ListView>

上面的代码可以编译，但是当我运行它时，它给我一个错误，“它仍然可以正常工作”，说“ SomethingViewModel”没有“ ToggleCommand”。

该怎么做？