Xamarin表单绑定按钮父BindingContext的命令 [英] Xamarin Forms binding button Command to parent BindingContext

问题描述

我正在编写Xamarin应用程序，发现无法跨越的WPF之间存在差异.

I'm writing Xamarin application and I found difference between WPF which I cannot cross.

我正在使用Xamarin Forms Labs来获得Repeater控件.

I'm using Xamarin Forms Labs to get Repeater control.

我有一个Repeater，它可以重复DataTemplate:

I have a Repeater, which repeats DataTemplate:

<DataTemplate>
  <Button Text="{Binding Text}" Command="{Binding CategorySelectedCommand}"  />
</DataTemplate>

但是我想将命令执行移到我的userControl绑定上下文中.

But i would like to move command execution to my userControl Binding Context.

通常使用WPF，它看起来像:

Normally with WPF it would look like:

Command={Binding ElementName=myUserControl, Path=DataContext.CategorySelectedCommand}

但是它没有ElementName属性.

But it does not have ElementName property.

我发现我可以像这样设置按钮的BindingContext:

I have found that I could set BindingContext of my button like this:

BindingContext="{x:Reference myUserControl}"

但是我不能将Text属性绑定到按钮的文本上.

But then I cannot bind Text property to my button's text.

我应该怎么做?

推荐答案

您可以使用Source属性指定将使用的绑定源，而不是当前的BindingContext.然后，文本可以来自页面的绑定上下文，而命令可以来自其他地方.

You can use the Source property to specify a source for the binding that will be used instead of the current BindingContext. Then the text can come from the page's binding context and the command from somewhere else.

Command="{Binding CategorySelectedCommand, Source={x:Static me:SomeStaticClass.YourUserControl}}"

或

Command="{Binding CategorySelectedCommand, Source={DynamicResource yourUserControlKey}}"

或

Command="{Binding CategorySelectedCommand, Source={x:Reference myUserControl}}"

这是一个完整的例子.一个常见的问题是不实现INotifyPropertyChanged并在对InitializeComponent()的调用之后将属性设置为.

Here's a complete example. A common problem is to not implement INotifyPropertyChanged and set the property after the call to InitializeComponent().

XAML

<?xml version="1.0" encoding="UTF-8"?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms" xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml" x:Class="test.MyPage" x:Name="ThePage">
    <Label Text="{Binding TextProp, Source={x:Reference ThePage}" HorizontalOptions="Center" VerticalOptions="CenterAndExpand" />
</ContentPage>

背后的代码

public partial class MyPage : ContentPage
{
    public MyPage ()
    {
        this.TextProp = "Some Text";
        InitializeComponent ();
    }

    public string TextProp
    {
        get;
        set;
    }
}

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