Xamarin.Forms bindingContext将源设置回root/parent

Question

我得到了ViewModel一个AddToFavoriteCommand没有被调用的命令().现在它只关注命令,而CustomPin class不是viewModel.我设置我viewModel的BindingContext代码页的后面.

但是因为它枚举了我的customPins集合,所以它会在那里查看命令.我需要回到根.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>

代码背后(删除了所有其他逻辑,例如我不需要的点击事件)

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

我的 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; }
}

Answer 1

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>

请注意我是如何将x:Name元素添加到页面根目录的.当然,那里有更多的属性,留在那里,但为了清楚起见,我把它们留在了这里.

其次,请注意我是如何从MenuItem绑定中引用该名称并添加的Path=BindingContext..这样它就会绑定到BindingContext名称所标识的元素,在我们的例子中ContentPage.

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