Xamarin MVVM自定义字体在数据模板中不起作用

Question

使用字体时遇到麻烦。当我执行以下操作时，效果很好。

FontFamily="{StaticResource IconFonts}" Text=""

但是如果我尝试动态绑定text属性，它将不起作用。

FontFamily="{DynamicResource IconFonts}" Text="{Binding Comments}"

它显示出所有异常。看起来它尝试做某事，但是没有完全渲染。这是完整的代码，下面包含我的测试。预先感谢。

<FlexLayout x:Name="FlexFood"
        Wrap="Wrap"
        Direction="Row"
        JustifyContent="Start"
        Padding="0, 10"
        BindableLayout.ItemsSource="{Binding FoodCollection}">
<BindableLayout.ItemTemplate>
    <DataTemplate>
        <StackLayout Padding="5, 0">

                    <Frame.GestureRecognizers>

                        <TapGestureRecognizer Tapped="OnTypesSelected"></TapGestureRecognizer>

                    </Frame.GestureRecognizers>

                    <Frame.Content>
                        <StackLayout x:Name="LayoutFood">

                            <StackLayout VerticalOptions="CenterAndExpand" HorizontalOptions="CenterAndExpand">
                                <Label x:Name="LabelTitle" Padding="0, 10">
                                <Label.FormattedText>
                                    <FormattedString>
                                        <Span FontSize="Subtitle" Text="{Binding Title}" FontAttributes="Bold"></Span>
                                        <Span Text=" "></Span>
                                        <Span FontSize="Subtitle" Text="{Binding Version}" FontAttributes="Bold"></Span>
                                    </FormattedString>
                                </Label.FormattedText>
                            </Label>
                            </StackLayout>

                            <StackLayout Orientation="Horizontal">

                            <StackLayout HorizontalOptions="StartAndExpand">

                                <Label Text="{Binding Description}" FontSize="Body"></Label>-->
                                <Label FontSize="Caption" TextColor="#LELELE">
                                    <Label.FormattedText>
                                        <FormattedString>
                                            <Span Text="{Binding fDepartment}"></Span>
                                            <Span Text="{Binding pType}"></Span>
                                        </FormattedString>
                                    </Label.FormattedText>
                                </Label>

                            </StackLayout>

                            <StackLayout HorizontalOptions="End">

                            <Label Text="{Binding Comments}"></Label>

                            <Label FontFamily="{StaticResource IconFonts}" Text="&#xf139;"></Label>

                            <Label x:Name="LabelTypeTest" FontFamily="{StaticResource IconFonts}"
                                    Text="{Binding Comments, StringFormat='&#xf123;'}"></Label>

                            <Label FontFamily="{DynamicResource IconFonts}" Text="{Binding Comments}"></Label>

                            <Image x:Name="ImageTypeTest">
                                <Image.Source>
                                    <FontImageSource Size="48" FontFamily="{StaticResource IconFonts}" Color="#000000"></FontImageSource>
                                </Image.Source>
                            </Image>

                            </StackLayout>

                            </StackLayout>

                        </StackLayout>
                    </Frame.Content>

            </helper:LayoutGradient>
        </StackLayout>
    </DataTemplate>
</BindableLayout.ItemTemplate>
</FlexLayout>

Answer 1

您如何设置动态资源？我相信它必须用代码完成，而不是XAML。请参阅以下文档：https://docs.microsoft.com/en-us/xamarin/xamarin-forms/user-interface/styles/xaml/dynamic

例如（以防关联文档消失）：

<ContentPage xmlns="http://xamarin.com/schemas/2014/forms" xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml" x:Class="Styles.DynamicStylesPage" Title="Dynamic" IconImageSource="xaml.png">
    <ContentPage.Resources>
        <ResourceDictionary>
            <Style x:Key="baseStyle" TargetType="View">
              ...
            </Style>
            <Style x:Key="blueSearchBarStyle"
                   TargetType="SearchBar"
                   BasedOn="{StaticResource baseStyle}">
              ...
            </Style>
            <Style x:Key="greenSearchBarStyle"
                   TargetType="SearchBar">
              ...
            </Style>
            ...
        </ResourceDictionary>
    </ContentPage.Resources>
    <ContentPage.Content>
        <StackLayout Padding="0,20,0,0">
            <SearchBar Placeholder="These SearchBar controls"
               Style="{DynamicResource searchBarStyle}" />
                ...
            </StackLayout>
    </ContentPage.Content>
</ContentPage>

后面的代码：

public partial class DynamicStylesPage : ContentPage
{
    bool originalStyle = true;

    public DynamicStylesPage ()
    {
        InitializeComponent ();
        Resources ["searchBarStyle"] = Resources ["blueSearchBarStyle"];
    }

    void OnButtonClicked (object sender, EventArgs e)
    {
        if (originalStyle) {
            Resources ["searchBarStyle"] = Resources ["greenSearchBarStyle"];
            originalStyle = false;
        } else {
            Resources ["searchBarStyle"] = Resources ["blueSearchBarStyle"];
            originalStyle = true;
        }
    }
}

您可以在上面看到searchBarStyle是如何创建和用作DynamicResource的，以及如何更改动态资源正在使用的基础资源。

但是，在没有看到更多代码的情况下，我不知道您是否已经进行了上述操作。