如何做亲属源模式在UWP中找到祖先(或等价物)

Question

我正在尝试做一些人认为应该非常简单的事情(至少在WPF中).我有一个包含listbox和datatemplate的页面,现在datatemplate调用了一个带有按钮的用户控件.没什么好看的,但是按钮命令不是listboxsource的一部分,我找不到一个简单的方法来告诉按钮在哪里查找命令.这是场景

<Page x:Class="App1.MainPage"
  xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
  xmlns:local="using:App1">
<Page.Resources>
    <DataTemplate x:Key="MyDataTemplate">
        <local:MyButton />
    </DataTemplate>
</Page.Resources>
<ListBox ItemTemplate="{StaticResource MyDataTemplate}" ItemsSource="{Binding Customers}" />
</Page>

<UserControl x:Class="App1.MyButton"
         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">

<Button Command="{Binding RelativeSource={RelativeSource Mode=FindAncestor, AncestorType=UserControl, AncestorLevel=2}, Path=DataContext.DeleteCommand}" Content="Delete" />
</UserControl>

请注意这不编译,因为在UWP中没有模式找到祖先？我应该怎么做,我一直在看谷歌但是找不到任何关于它的东西.

谢谢

Answer 1

答案是依赖属性.我有同样的问题.首先,如果您没有涉及DataTemplate,那么解决方案是直截了当的:

(this.Content as FrameworkElement).DataContext = this;

您在其构造函数中将UserControl的DataContext设置为其后面的代码.

如果您计划在DataTemplate中使用Command,那么您也需要DependecyProperty.

例:

 <DataTemplate>
     <Button Command="{Binding DataContext.MyCommand, ElementName=ParentName}">
 </DataTemplate>

要备份它,您需要为该命令创建一个依赖项属性:

 public ICommand MyCommand
    {
        get { return (ICommand)GetValue(MyCommandProperty); }
        set { SetValue(MyCommandProperty, value); }
    }

    // Using a DependencyProperty as the backing store for MyCommand.  This enables animation, styling, binding, etc...
    public static readonly DependencyProperty MyCommandProperty =
        DependencyProperty.Register("MyCommand", typeof(ICommand), typeof(ownerclass), new PropertyMetadata(0));

因此,现在当您使用用户控件时,您将拥有一个MyCommand属性,只要模板化父项与您提供的项匹配,您就可以绑定到ViewModel中的任何命令,并且参数也绑定到实际项目.控制是其中的一部分.

<usercontrols:button MyCommand="{Binding MyCommandFromViewModel}" CommandParameter="{Binding}"/>

简单的例子:

UserControl代码背后

 public sealed partial class ListviewUserControl : UserControl
{
    public ListviewUserControl()
    {
        this.InitializeComponent();

        (this.Content as FrameworkElement).DataContext = this;
    }




    public ICommand ButtonCommand
    {
        get { return (ICommand)GetValue(ButtonCommandProperty); }
        set { SetValue(ButtonCommandProperty, value); }
    }

    // Using a DependencyProperty as the backing store for ButtonCommand.  This enables animation, styling, binding, etc...
    public static readonly DependencyProperty ButtonCommandProperty =
        DependencyProperty.Register("ButtonCommand", typeof(ICommand), typeof(ListviewUserControl), new PropertyMetadata(null));




    public ObservableCollection<Item> ItemsSource
    {
        get { return (ObservableCollection<Item>)GetValue(ItemsSourceProperty); }
        set { SetValue(ItemsSourceProperty, value); }
    }

    // Using a DependencyProperty as the backing store for ItemsSource.  This enables animation, styling, binding, etc...
    public static readonly DependencyProperty ItemsSourceProperty =
        DependencyProperty.Register("ItemsSource", typeof(ObservableCollection<Item>), typeof(ListviewUserControl), new PropertyMetadata(new ObservableCollection<Item>()));



}

UserControl Xaml:

<Grid>
    <ListView ItemsSource="{Binding ItemSource}" x:Name="ListView">
        <ListView.ItemTemplate>
            <DataTemplate>
                <!--some item related content-->
                <AppBarButton Icon="Delete" Command="{Binding ButtonCommand, ElementName=ListView}" CommandParameter="{Binding}"/>
            </DataTemplate>
        </ListView.ItemTemplate>
    </ListView>
</Grid>

Page.xaml中的用法:

<Controls:ListviewUserControl ItemsSource="{Binding ViewModelsItemsList}" ButtonCommand="{Binding ViewModelsCommand}"/>