Xamarin Forms构建错误 - 找不到关键的StaticResource

Question

我刚学习XAML和Xamrin。我试图了解静态样式的工作原理。这是我的XAML代码：

<?xml version="1.0" encoding="utf-8" ?> 
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms" 
      xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml" 
      xmlns:local="clr-namespace:Styles" 
      x:Class="Styles.MainPage"> 

    <ContentPage.Resources> 
     <ResourceDictionary> 
      <Style x:key="buttonStyle" TargetType="Button"> 
       <Setter Property="HorizontalOptions" Value="Center"/> 
       <Setter Property="VerticalOptions" Value="Center" /> 
       <Setter Property="TextColor" Value="Red"/> 
       <Setter Property="FontSize" Value="Small"/> 
      </Style> 
      <Style TargetType="Label"> 
       <Setter Property="HorizontalOptions" Value="Center"/> 
       <Setter Property="VerticalOptions" Value="Center" /> 
       <Setter Property="TextColor" Value="Blue"/> 
       <Setter Property="FontSize" Value="20"/> 
      </Style> 
      <Style x:key="baseStyle" TargetType="View"> 
       <Setter Property="HorizontalOptions" Value="Center"/> 
       <Setter Property="VerticalOptions" Value="Center" /> 
      </Style> 
      <Style x:key="entryStyle" TargetType="Entry" BasedOn="{StaticResource baseStyle}"> 
       <Setter Property="TextColor" Value="Green"/> 
      </Style> 
     </ResourceDictionary> 
    </ContentPage.Resources> 

    <ContentPage.Content> 
     <StackLayout Padding="20"> 
      <Label Text="This is label 1 using implicit style"/> 
      <Label Text="This is label 2"/> 
      <Button 
       Text="Not using the button style" 
        BorderWidth="2" 
       HorizontalOptions="Center" 
       VerticalOptions="Center" 
        WidthRequest="200"/> 
      <Button Style="{StaticResource buttonStyle}" 
        Text="Using explicit style" 
        BorderWidth="2" 
        WidthRequest="200"/> 
      <Entry Style="{StaticResource entryStyle}" Placeholder="This enty uses an inherited style"/> 

      <Button Style="{StaticResource buttonStyle}" 
        Text="Using explicit style" 
        BorderWidth="2" 
        WidthRequest="200"/> 
     </StackLayout> 
    </ContentPage.Content> 
</ContentPage> 

编译工作正常，但在运行的时候，我得到这个异常：

[ERROR] FATAL UNHANDLED EXCEPTION: Xamarin.Forms.Xaml.XamlParseException: Position 25:58. StaticResource not found for key baseStyle 

我不明白为什么我得到这个错误，因为风格“键”已在前一行定义。任何帮助是极大的赞赏。

Answer 1

x:Key属性的首字母必须大写。

<?xml version="1.0" encoding="utf-8" ?> 
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms" 
      xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml" 
      xmlns:local="clr-namespace:Styles" 
      x:Class="Styles.MainPage"> 

    <ContentPage.Resources> 
     <ResourceDictionary> 
      <Style x:Key="buttonStyle" TargetType="Button"> 
       <Setter Property="HorizontalOptions" Value="Center"/> 
       <Setter Property="VerticalOptions" Value="Center" /> 
       <Setter Property="TextColor" Value="Red"/> 
       <Setter Property="FontSize" Value="Small"/> 
      </Style> 
      <Style TargetType="Label"> 
       <Setter Property="HorizontalOptions" Value="Center"/> 
       <Setter Property="VerticalOptions" Value="Center" /> 
       <Setter Property="TextColor" Value="Blue"/> 
       <Setter Property="FontSize" Value="20"/> 
      </Style> 
      <Style x:Key="baseStyle" TargetType="View"> 
       <Setter Property="HorizontalOptions" Value="Center"/> 
       <Setter Property="VerticalOptions" Value="Center" /> 
      </Style> 
      <Style x:Key="entryStyle" TargetType="Entry" BasedOn="{StaticResource baseStyle}"> 
       <Setter Property="TextColor" Value="Green"/> 
      </Style> 
     </ResourceDictionary> 
    </ContentPage.Resources> 

    <ContentPage.Content> 
     <StackLayout Padding="20"> 
      <Label Text="This is label 1 using implicit style"/> 
      <Label Text="This is label 2"/> 
      <Button 
       Text="Not using the button style" 
        BorderWidth="2" 
       HorizontalOptions="Center" 
       VerticalOptions="Center" 
        WidthRequest="200"/> 
      <Button Style="{StaticResource buttonStyle}" 
        Text="Using explicit style" 
        BorderWidth="2" 
        WidthRequest="200"/> 
      <Entry Style="{StaticResource entryStyle}" Placeholder="This enty uses an inherited style"/> 

      <Button Style="{StaticResource buttonStyle}" 
        Text="Using explicit style" 
        BorderWidth="2" 
        WidthRequest="200"/> 
     </StackLayout> 
    </ContentPage.Content> 
</ContentPage>