使用DataBinding Xamarin表单旋转标签 [英] Rotating Label with DataBinding Xamarin Forms

问题描述

我正在尝试复制

I am trying to duplicate the following example to understand binding in Xamarin.

一旦我运行以下脚本，我的第一个标签就不会随着滑块一起旋转.

Once I run the following script, my first label is not rotating along with slider.

<?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="DataBinding.MyPage" Title="Slider Bindings Page">
 <StackLayout>
    <Label Text="ROTATION"
           BindingContext="{x:Reference Name=slider}"
           Rotation="{Binding Path=Value}"
           Font="Bold, Large"
           HorizontalOptions="Center"
           VerticalOptions="CenterAndExpand" />

    <Slider x:Name="slider"
            Maximum="360"
            VerticalOptions="CenterAndExpand" />

    <Label BindingContext="{x:Reference slider}"
           Text="{Binding Value, 
                          StringFormat='The angle is {0:F0} degrees'}"
           Font="Large"
           HorizontalOptions="Center"
           VerticalOptions="CenterAndExpand" />
  </StackLayout>


</ContentPage>

推荐答案

XAML 页面上过去一直要求使用 {x:Reference} 在引用之前将要引用的控件显示在标记中.

It used to be a requirement in XAML pages that any use of {x:Reference} had to have the control that was being referenced appear in the markup prior to it being referenced.

即

在 Xamarin.Forms SliderBindings 示例中，我们最初具有以下标记，该标记可用于 Xamarin.Forms 1.22x :-

In the Xamarin.Forms SliderBindings example we had the following markup originally that works with Xamarin.Forms 1.22x:-

<StackLayout>
    <Slider x:Name="slider"
            Maximum="360"
            VerticalOptions="CenterAndExpand" />

    <Label Text="ROTATION"
           BindingContext="{x:Reference Name=slider}"
           Rotation="{Binding Path=Value}"
           Font="Bold, Large"
           HorizontalOptions="Center"
           VerticalOptions="CenterAndExpand" />

    <Label BindingContext="{x:Reference slider}"
           Text="{Binding Value, 
                          StringFormat='The angle is {0:F0} degrees'}"
           Font="Large"
           HorizontalOptions="Center"
           VerticalOptions="CenterAndExpand" />
</StackLayout>

但是，现在，在最新版本的 Xamarin.Forms v1.2.3.6257 中，您不再需要在 {x:Referenced} 中放置控件.文档，如其更新示例所示:-

However, now in the latest version of Xamarin.Forms v1.2.3.6257 you no longer have to place controls prior to them being {x:Referenced} in a document, as can be seen by their updated example:-

<StackLayout>
    <Label Text="ROTATION"
           BindingContext="{x:Reference Name=slider}"
           Rotation="{Binding Path=Value}"
           Font="Bold, Large"
           HorizontalOptions="Center"
           VerticalOptions="CenterAndExpand" />

    <Slider x:Name="slider"
            Maximum="360"
            VerticalOptions="CenterAndExpand" />

    <Label BindingContext="{x:Reference slider}"
           Text="{Binding Value, 
                          StringFormat='The angle is {0:F0} degrees'}"
           Font="Large"
           HorizontalOptions="Center"
           VerticalOptions="CenterAndExpand" />
  </StackLayout>

因此，如果您将项目更新到最新的 Xamarin.Forms v1.2.3.6257 ，则可以进行 {x:Reference} 控件，而无需订购控制很重要.可能还会有某些限制，但是它似乎比以前的版本灵活得多.

So if you update your project to the latest Xamarin.Forms v1.2.3.6257, you will then be able to {x:Reference} controls without ordering of controls being important. There may be certain restrtictions still, however it seems much more flexible than in previous versions.

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