使用Xamarin.Forms中的View Model属性绑定到StaticResource? [英] Binding to StaticResource with a property of View Model in Xamarin.Forms?

问题描述

我在ResourceDictionary中定义了一些自定义字体

I have some custom fonts defined in ResourceDictionary

<Application xmlns="http://xamarin.com/schemas/2014/forms"
         xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
         x:Class="Fonlow.VA.App">
<Application.Resources>
    <ResourceDictionary>
        <OnPlatform x:TypeArguments="x:String" x:Key="SuperFont">
            <On Platform="Android" Value="Super.ttf#Super" />
            <On Platform="UWP" Value="/Assets/Super.ttf#Super" />
            <!--<On Platform="iOS" Value="OpenSans-Bold" />-->
        </OnPlatform>
        <OnPlatform x:TypeArguments="x:String" x:Key="NormalFont">
            <On Platform="Android" Value="Normal.ttf#Normal" />
            <On Platform="UWP" Value="/Assets/Normal.ttf#Normal" />
            <!--<On Platform="iOS" Value="OpenSans-Bold" />-->
        </OnPlatform>
    </ResourceDictionary>
</Application.Resources>

还有

  <Label Text="{Binding CurrentOptotype.Text}" FontFamily="{StaticResource SuperFont}" FontSize="{Binding CurrentFontSize}" TextColor="Black" />

到目前为止，一切都很好.但是，我将在运行时通过ViewModel绑定切换FontFamily，就像FontSize的绑定一样，因为CurrentFontSize是View模型中的一个属性. 我尝试过:

So far so good. However, I would switch the FontFamily at runtime through ViewModel binding just like the binding for FontSize, since CurrentFontSize is a property in the View Model. I had tried:

FontFamily="{Binding CurrentFontFamily}"

并且CurrentFontFamily的值可以指向现有的系统字体，但是我想指向一个自定义字体，该字体指向ResourceDictionary中定义的字体.

And the value of CurrentFontFamily can point to an existing system font, but I want to point to a custom font pointing to what defined in ResourceDictionary.

然后我尝试了:

FontFamily="{StaticResource {Binding CurrentFontFamily}}"

显然，针对这种构成语法存在运行时错误.我只是想知道XAML中是否存在通过MVVM View Model在运行时切换自定义字体的方法?

And there's runtime error obviously against such makeup syntax. I just wonder whether there's a in XAML to switch custom font at runtime through MVVM View Model?

推荐答案

数据触发器是解决之道，如

Data Trigger is the way to go, as explained in https://blog.xamarin.com/triggers-in-xamarin-forms/. Following the example there, now I have:

                    <Label Text="{Binding CurrentText}"  Grid.Column="1" Margin="5,0,0,0"
                       FontSize="{Binding CurrentFontSize}" TextColor="Black"
                   HorizontalTextAlignment="Start" VerticalTextAlignment="Center">
                    <Label.Triggers>
                        <DataTrigger TargetType="Label"
                                     Binding="{Binding Source={x:Reference fontSelected}, Path=SelectedIndex}"
                                     Value="0">
                            <Setter Property="FontFamily" Value="{StaticResource NormalFont}"/>
                        </DataTrigger>
                        <DataTrigger TargetType="Label"
                                     Binding="{Binding Source={x:Reference chartSelected}, Path=SelectedIndex}"
                                     Value="1">
                            <Setter Property="FontFamily" Value="{StaticResource SuperFont}"/>
                        </DataTrigger>

                    </Label.Triggers>
                </Label>

这篇关于使用Xamarin.Forms中的View Model属性绑定到StaticResource?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！