Xamarin Forms 选项卡式页面触发器属性不起作用

Question

我正在尝试关注这个 sample 通过使用 font awesome 作为选项卡式页面的图标并使用触发器更改字体颜色但是当我想使用 font awesome 应用样式时，出现错误属性="IsChecked" 对于目标不存在。我在示例中注意到他们正在使用 shell，我如何使用常规选项卡式页面复制该示例？

在 app.XAML 我有以下

<OnPlatform x:TypeArguments="x:String" 
            x:Key="FontAwesomeSolid">
            <On Platform="Android" 
            Value="Font5Solid.otf#Regular" />
            <On Platform="iOS" 
            Value="FontAwesome5Free-Solid" />
         </OnPlatform>
         <OnPlatform x:TypeArguments="x:String" 
            x:Key="FontAwesomeRegular">
            <On Platform="Android" 
            Value="Font5Regular.otf#Regular" />
            <On Platform="iOS" 
             Value="FontAwesome5Free-Regular" />
          </OnPlatform>

对于标签页我有以下内容

<?xml version="1.0" encoding="utf-8"?>
<TabbedPage x:Name="Tab" xmlns="http://xamarin.com/schemas/2014/forms" xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml" x:Class="pages.Views.HomeTabbedPage">
    <!--Pages can be added as references or inline-->

    <TabbedPage.Resources>
          <ResourceDictionary>
     <Style TargetType="Tab" x:Key="FollowTab">
                <Style.Triggers>
                <Trigger TargetType="TabbedPage"
                         Property="IsChecked" Value="False">
                    <Setter Property="Icon" >
                        <Setter.Value>
                            <FontImageSource FontFamily="{StaticResource FontAwesomeRegular}" Glyph="&#xf004;"/>
                        </Setter.Value>
                    </Setter>
                </Trigger>
                <Trigger TargetType="Tab" 
                         Property="IsChecked" Value="True">
                    <Setter Property="Icon" >
                        <Setter.Value>
                            <FontImageSource FontFamily="{StaticResource FontAwesomeSolid}" Glyph="&#xf004;"/>
                        </Setter.Value>
                    </Setter>
                </Trigger>
                </Style.Triggers>
            </Style>
  </ResourceDictionary>
    </TabbedPage.Resources>

    <ContentPage Title="sample page"  />
    
</TabbedPage>

Answer 1

要在正常 TabbedPage 中复制它，您可以尝试以下步骤：

1 - 创建一个转换器来检查 TabbedPage.CurrentPage 类型：

public class SelectedTabTypeConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        if (value == null)
            return null;

        if (!(value is Page))
            throw new ArgumentException("Expected value to be of type " + nameof(Page), nameof(value));

        // if value is a NavigationPage check against its RootPage
        if (value is NavigationPage navPage)
            return navPage.RootPage?.GetType();

        return value.GetType();
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture) 
        => throw new NotImplementedException();
}

2 - 将 x:Name 属性添加到 TabbedPage 以便我们稍后可以引用它：

<TabbedPage x:Name="MyTabbedPage" ...

3 - 将转换器资源添加到 TabbedPage.Resources:

  <TabbedPage.Resources>
    <ResourceDictionary>
      <converters:SelectedTabTypeConverter x:Key="SelectedTabTypeConverter" />
    </ResourceDictionary>
  </TabbedPage.Resources>

4 - 添加页面和 DataTriggers:

  <TabbedPage.Children>
    <!-- Normal page tab default values -->
    <views:OnePage Title="Page1">
      <views:OnePage.Triggers>
        <DataTrigger 
            TargetType="views:OnePage"
            Binding="{Binding Source={x:Reference MyTabbedPage}, Path=CurrentPage, Converter={StaticResource SelectedTabTypeConverter}}" 
            Value="{x:Type views:OnePage}">
          <Setter Property="Title" Value="Page1 Selected" />
        </DataTrigger>
      </views:OnePage.Triggers>
    </views:OnePage>

    <!-- NavigationPage tab -->
    <NavigationPage Title="Page2">
      <x:Arguments>
        <views:TwoPage />
      </x:Arguments>
      <NavigationPage.Triggers>
        <DataTrigger 
            TargetType="NavigationPage" 
            Binding="{Binding Source={x:Reference MyTabbedPage}, Path=CurrentPage, Converter={StaticResource SelectedTabTypeConverter}}" 
            Value="{x:Type views:TwoPage}">
          <Setter Property="Title" Value="Page2 Selected" />
        </DataTrigger>
      </NavigationPage.Triggers>
    </NavigationPage>
  </TabbedPage.Children>

Xamarin Forms 选项卡式页面触发器属性不起作用

Xamarin Forms Tabbed Page Trigger properties not working

xaml

eventtrigger

font-awesome

xamarin.forms

tabbedpage