是否有可能以一种颜色资源指向Xamarin.Forms另一种颜色的资源？ [英] Is it possible to point one Color resource to another Color resource in Xamarin.Forms?

问题描述

我建立一个 Xamarin形式应用程序，我目前正在起草我的应用程序资源，主要是我的色彩。

I am building a Xamarin Forms Application and I am currently drawing up my application Resources, mainly my colours.

例如我有以下几点：

  <Color x:Key="Slate">#404040</Color>
  <Color x:Key="Blue">#458623</Color>

  <Color x:Key="SelectedItemColour">#458623</Color>

正如你可以看到我的 SelectedItemColour 是同为蓝色

我曾尝试以下，但它没有工作：

I have tried the following but it didn't work:

  <Color x:Key="Slate">#404040</Color>
  <Color x:Key="Blue">#458623</Color>

  <Color x:Key="SelectedItemColour" Color="{StaticResource Blue}"/>

我知道，如果 WPF 你可以做这里回答既定

I know if WPF you can do the answer stated here

是否有可能指向一个彩色资源在Xamarin.Forms另一个彩色资源？

Is it possible to point a Colour Resource to another Colour Resource in Xamarin.Forms?

推荐答案

所以，这样我不得不这样做，这是非常复杂，所以仔细聆听。

So the way I had to do this was very complex so listen carefully.

我发现真正的问题在这里是我需要主题我的Xamarin.Forms的应用程序。

I found that the real problem here was that I needed to "Theme" my Xamarin.Forms application.

因此，继承人什么我。

首先做出了抽象主题类：

public abstract class Theme
{
    public Dictionary<string, Color> Colours { get; set; } = new Dictionary<string, Color>();

    protected void DictionaryThemes(Type type)
    {
        var properties = type.GetRuntimeProperties();
        foreach (PropertyInfo propInfo in properties)
        {
            if (propInfo.PropertyType == typeof(Color))
            {
                var key = propInfo.Name;
                var value = propInfo.GetValue(this);
                Colours.Add(key, (Color)value); 
            }
        }
    }

    public abstract Color TitleColour { get; }
}

通过使用反射一个很好的方法来填充字典充满了我的资源

With a nice method using reflection to fill a dictionary full of my Resources

然后我扩展这个类与我实际的主题：

I then extended this class with my actual theme:

public class MyTheme : Theme
{
    public MyTheme()
    {
        DictionaryThemes(typeof(MyTheme));
    }

    //Slate
    public override Color TitleColour { get; } = Color.FromHex("#00ff00");
}

还是和我在一起？好...

Still with me? good...

然后我不得不加载这个主题到我的应用程序资源并与我的其他应用程序进行合并资源。我不得不从其他资源分割 MyTheme的资源，这样我可以在我的主<$ C $使用C>资源更新的文件。

I then had to load this theme into my Application Resources and merge it with my other application resources. I have to split the MyTheme resource from the other Resources so that I can use it in my main Resources file later.

让我告诉你，这是我的 CurrentTheme 资源文件：

Let me show you, here is my CurrentTheme resource file:

<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             xmlns:styling="clr-MyApp.Styling;assembly=MyApp"
             x:Class="MyApp.Styling.CurrentTheme">
  <ContentPage.Resources>
    <ResourceDictionary>
  <styling:MyTheme x:Key="CurrentTheme"/>
</ResourceDictionary>

我有做一个网页的一部分， Xamarin.Forms 的密封的 ResourceDictionary中类的（见这里）这意味着你不能扩展它，并创建自己的..耻辱。 。无论如何，我离题

I have to do it as part of a page as Xamarin.Forms has Sealed the ResourceDictionary class (see here) meaning you can't extend it and create your own.. Shame. Anyway I digress.

然后我把我的应用程序资源，以 CurrentTheme 像这样：

I then set my application Resources to CurrentTheme like so:

 var currentTheme = new CurrentTheme();
 Xamarin.Forms.Application.Current.Resources = currentTheme.Resources;

然后我可以在其他风格的合并从我的主资源文件，在这种情况下，所谓的样式：

I can then merge in other styles from my main Resource file, in this case called Styles:

<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             xmlns:styling="clr-MyApp.Styling;assembly=MyApp"
             x:Class="MyApp.Styling.Styles">
  <ContentPage.Resources>
    <ResourceDictionary>
       <Style x:Key="TitleStyle" TargetType="Label">
          <Setter Property="FontAttributes" Value="Bold" />
          <Setter Property="FontSize" Value="30" />
          <Setter Property="TextColor" Value="{styling:Colour TitleColour}" />
       </Style>
</ResourceDictionary>

我合并这为我的主要应用程序资源，像这样：

I merge this into my main application resources like so:

 var styles = new Styles();
 foreach (var item in styles.Resources)
 {
       Application.Current.Resources.Add(item.Key,item.Value);
 }

现在，你可以看到setter属性之一，在样式类看起来像这样：

Now as you can see one of the setter properties in the Styles class looks like so:

和你说什么是价值呢？

下面来拼图的最后一块。扩展方法，它允许您定义 XAML 象上面。

Here comes the final piece of the puzzle. An extension method that allows you to define your xaml like the above.

首先在 ColourExtension 类：

// You exclude the 'Extension' suffix when using in Xaml markup
[ContentProperty("Text")]
public class ColourExtension : IMarkupExtension
{
    public string Text { get; set; }

    public object ProvideValue(IServiceProvider serviceProvider)
    {
        if (Text == null)
            throw new Exception("No Colour Key Provided");

        return StylingLookup.GetColour(Text);
    }
}

和最后的 StylingLookup 类：

public static class StylingLookup
{
    public static Color GetColour(string key)
    {
        var currentTheme = (Application.Current.Resources["CurrentTheme"] as Theme);

        return currentTheme.Colours[key];
    }
}

现在，这一切是有道理的，为什么我们不得不拆分 CurrentTheme 从主样式资源。由于该行的：

And now it all makes sense, Why we had to split CurrentTheme from the main Styles resources. Because of the line:

var currentTheme = (Application.Current.Resources["CurrentTheme"] as Theme);

如果任何人有一个更好的模式来的造型的应用我喜欢听到它

If anyone has a better pattern for Styling an application I'd love to hear it

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