将一个控件的值传递给转换器以设置另一个控件的宽度 [英] Pass the value of one control to a Converter to set the width on another control

问题描述

我要根据文本容器的宽度设置文本块的宽度，减去在文本块上设置的边距.

I want to set the width of a TextBlock based on the width of its container, minus the margins set on the TextBlock.

这是我的代码:

<TextBlock x:Name="txtStatusMessages" 
           Width="{Binding ElementName=LayoutRoot,Path=ActualWidth }"
                   TextWrapping="WrapWithOverflow" 
           Foreground="White" 
           Margin="5,5,5,5">This is a message
</TextBlock>

这很好用，除了由于将左右边距设置为5而导致TextBlock太大了10个单位之外.

And that works great except for the fact that the TextBlock is 10 units too big due to the Left and Right Margins bbeing set to 5.

好，所以我想...让我们使用转换器.但是我不知道如何传递我的容器控件的ActualWidth(见上:LayoutRoot).

OK, so I thought... Let's use a Converter. But I don't know how to pass the ActualWidth of my container control (SEE ABOVE: LayoutRoot).

我知道如何使用转换器，甚至是带有参数的转换器，只是没有像...这样的参数... Binding ElementName = LayoutRoot，Path = ActualWidth

I know how to use converters, and even converters with parameters, just not a parameter like... Binding ElementName=LayoutRoot,Path=ActualWidth

例如，我无法完成这项工作:

For example, I can't make this work:

Width="{Binding Converter={StaticResource PositionConverter},  
       ConverterParameter={Binding ElementName=LayoutRoot,Path=ActualWidth }}"

我希望我已经说得足够清楚了，希望您能有所帮助，因为Google今晚对我没有帮助.

I hope I made this clear enough and hope that you can help because Google is no help for me tonight.

推荐答案

您应该将另一个控件用作源，而不是参数. 该参数必须为常量，在您的情况下可以为-5.

you're supposed to use the other control as the source, not the parameter. The parameter has to be a constant and in your case can be -5.

我目前不在VS附近，因此语法可能不准确，但是它类似于:

I'm not near VS at the moment so the syntax maybe inaccurate, however, it is something like:

Width="{Binding ElementName=LayoutRoot, Path=ActualWidth,
Converter={StaticResource PositionConverter}, ConverterParameter=-5}"

(转换器将接收-5作为字符串，并且在使用前必须将其转换为数字.)

(The converter will receive -5 as a string and will have to convert it into a number before using it.)

根据我的经验，最好使用DependecyProperty XXX的OnXXXChanged回调，并且不要将同一窗口/根控件中的控件彼此绑定. 原因之一是您稍后可能希望将它们绑定到外部元素.

From my experience it is better to use the OnXXXChanged callback of DependecyProperty XXX, and not bind controls within the same window/root control one to another. One of the reasons for this is that you may want to bind them to an external element later on.

或者，使用多重绑定:

<TextBlock>
    <TextBlock.Width>
        <MultiBinding Converter="{StaticResource yourConverter}">
            <MultiBinding.Bindings>
                <Binding /> <!-- Bind to parameter 1 here -->
                <Binding /> <!-- Bind to parameter 2 here -->
          </MultiBinding.Bindings>
        </MultiBinding>
    </TextBlock.Width>
</TextBlock>

和一个将两个参数转换为所需值的转换器.

and and a converter which converts the two parameters to the value you want.

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