Xamarin 表单:如何引用父绑定

问题描述

<ViewCell> 
   <ViewCell.View>
      <Label Text="{Binding ABC}"></Label>
   </ViewCell.View>
</ViewCell>

假设这个视单元在 ListView 内.如果内容页面与视图模型绑定，我如何获得对内容页面绑定的引用.目前，ABC"正在引用列表中某个对象的属性，但我想从内容页面的 bindingcontext 中获取该值.

Assuming this viewcell was inside ListView. If the content page was binding with a view model, how can I get a reference to the content page's binding. Currently, 'ABC' is referencing the property of an object in the list but i want to get the value from the content page's bindingcontext.

<ffimageloading:CachedImage.GestureRecognizers>
   <TapGestureRecognizer BindingContext="{x:Reference page}" Command="{Binding OnSignInCommand}" CommandParameter="{Binding Model}" />
</ffimageloading:CachedImage.GestureRecognizers>

推荐答案

@qubuss 在下面给出了正确答案，但我想提供更多上下文并展示示例以使其更清楚:

@qubuss gave the correct answer below, but I would like to give more context and show an example to make it more clear:

让我们考虑以下页面:

<ContentPage  
    xmlns="http://xamarin.com/schemas/2014/forms" 
    xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
    x:Name="firstPage" -->this reference parent context
    x:Class="Your_Class_Name">
  <ListView x:Name="ListSource"
            ItemsSource="{Binding ListSource}" >
            <ListView.ItemTemplate>
               <DataTemplate>
                   <ViewCell>
                        <Grid>
                         // this come from item source
                    <Label Text="{Binding ABC}"></Label>
                    <Button Command="{Binding BindingContext.CommandFromParent
                           , Source={x:Reference firstPage} }" />
                        </Grid>
                                                
                       </ViewCell>
                  /DataTemplate>
           </ListView.ItemTemplate>
    </ListView>


</ContentPage>

你的视图模型应该是这样的

your view Model should look like that

 public class ViewModelName 
    {
        private List<YourDataType> _listSource = new List<YourDataType>();
        

        public List<YourDataType> ListSource
        {
            get => _listSource;
            set
            {
                _listSource = value;
                RaisePropertyChanged();
            }
        }

        public ICommand CommandFromParent => new Command(HandleYourActionHere);

}
}

说明当我们编写BindingContext.CommandFromParent时，BindingContext代表firstPage(x:Name=firstPage")的BindingContext，其类型为ViewModelName

ExplanationWhen we write BindingContext.CommandFromParent, BindingContext represents the BindingContext of firstPage(x:Name="firstPage") which is of type ViewModelName

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