Xamarin.Forms bindingContext 将源设置回 root/parent

I got a ViewModel用命令（AddToFavoriteCommand）不会被调用。现在它只关注中的命令CustomPin class，不是viewModel。我正在设置我的viewModel to the BindingContext后面的代码中的页面。

但由于它枚举了我的自定义引脚集合，因此它会照顾那里的命令。我需要回到根源。我可能需要更改源但无法使其工作。

<ContentPage.Content>
    <StackLayout>
        <AbsoluteLayout>
            <Button Text="{Binding Filter}" Command="{Binding GotoFilterPageCommand}" />
        </AbsoluteLayout>
        <ListView x:Name="ListView" RowHeight="60" ItemsSource="{Binding CustomPins}" ItemSelected="OnItemSelected">
            <ListView.ItemTemplate>
                <DataTemplate>
                    <ViewCell>
                        <ViewCell.ContextActions>
                            <MenuItem Text="Favorite" Command="{Binding AddToFavoriteCommand}" />
                            <MenuItem Text="..." CommandParameter="{Binding .}" Clicked="OnMoreClicked" />
                        </ViewCell.ContextActions>
                        <StackLayout Padding="5" Orientation="Vertical" >
                            <Label Text="{Binding ParkingLot.Street}" FontSize="Medium" />
                        </StackLayout>
                    </ViewCell>
                </DataTemplate>
            </ListView.ItemTemplate>
        </ListView>
    </StackLayout>
</ContentPage.Content>

代码隐藏（删除了我不需要的所有其他逻辑，例如单击事件）

[XamlCompilation(XamlCompilationOptions.Compile)]
public partial class ParkingListPage : ContentPage
{
    public ParkingListPage()
    {
        InitializeComponent();
        BindingContext = new ParkingListViewModel();
    }
}

My ViewModel

public class ParkingListViewModel
{
    public ParkingListViewModel()
    {
        AddToFavoriteCommand = new Command(Test);
    }

    private void Test()
    {
    }

    public IEnumerable<CustomPin> CustomPins { get; set; } = SampleParkings.Parkings;

    public Command AddToFavoriteCommand { get; }
}

试试这样：

<ContentPage x:Name="YourPageName">
    <ContentPage.Content>
        <StackLayout>
            <AbsoluteLayout>
                <Button Text="{Binding Filter}" Command="{Binding GotoFilterPageCommand}" />
            </AbsoluteLayout>
            <ListView x:Name="ListView" RowHeight="60" ItemsSource="{Binding CustomPins}" ItemSelected="OnItemSelected">
                <ListView.ItemTemplate>
                    <DataTemplate>
                        <ViewCell>
                            <ViewCell.ContextActions>
                                <MenuItem Text="Favorite" Command="{Binding Path=BindingContext.AddToFavoriteCommand, Source={x:Reference YourPageName}}" />
                                <MenuItem Text="..." CommandParameter="{Binding .}" Clicked="OnMoreClicked" />
                            </ViewCell.ContextActions>
                            <StackLayout Padding="5" Orientation="Vertical" >
                                <Label Text="{Binding ParkingLot.Street}" FontSize="Medium" />
                            </StackLayout>
                        </ViewCell>
                    </DataTemplate>
                </ListView.ItemTemplate>
            </ListView>
        </StackLayout>
    </ContentPage.Content>
</ContentPage>

请注意我如何添加x:Name元素到页面的根目录。当然，还有更多属性，请将它们留在那里，但为了清楚起见，我在这里将它们省略了。

其次，请注意我如何从MenuItem绑定并添加Path=BindingContext.。这样它将绑定到BindingContext由名称标识的元素，在我们的例子中ContentPage.

可以在此处找到示例项目：https://github.com/jfversluis/SampleParentBinding