更新通用Windows App XAML中的资源

几个月前，我遇到了同样的问题，直到遇到以下博客文章，提出了一个很好的通用解决方案后，我才能解决该问题。

基本上，您需要做的是：

第一的

添加以下帮助程序Frame类，它将替换您的默认帮助程序类Frame

public class ThemeAwareFrame : Frame
{
    private static readonly ThemeProxyClass _themeProxyClass = new ThemeProxyClass();

    public static readonly DependencyProperty AppThemeProperty = DependencyProperty.Register(
        "AppTheme", typeof(ElementTheme), typeof(ThemeAwareFrame), new PropertyMetadata(default(ElementTheme), (d, e) => _themeProxyClass.Theme = (ElementTheme)e.NewValue));


    public ElementTheme AppTheme
    {
        get { return (ElementTheme)GetValue(AppThemeProperty); }
        set { SetValue(AppThemeProperty, value); }
    }

    public ThemeAwareFrame(ElementTheme appTheme)
    {
        var themeBinding = new Binding { Source = _themeProxyClass, Path = new PropertyPath("Theme"), Mode = BindingMode.OneWay };
        SetBinding(RequestedThemeProperty, themeBinding);
        AppTheme = appTheme;

    }
    sealed class ThemeProxyClass : INotifyPropertyChanged
    {
        private ElementTheme _theme;

        public ElementTheme Theme
        {
            get { return _theme; }
            set
            {
                _theme = value;
                OnPropertyChanged();
            }
        }

        public event PropertyChangedEventHandler PropertyChanged;

        private void OnPropertyChanged([CallerMemberName] string propertyName = null)
        {
            PropertyChangedEventHandler handler = PropertyChanged;
            if (handler != null) handler(this, new PropertyChangedEventArgs(propertyName));
        }
    }
}

ThemeAwareFrame博客文章撰写者解释的该类背后的思想是：

我创建一个代理类，该代理类将仅用于存储当前主题，并且，如果更改了主题，则将其传播。这是一个静态字段，因此与所有ThemeAwareFrame共享。

我添加了一个AppTheme依赖项属性。更改后，它将在代理类中更改。

在ThemeAwareFrame构造函数中，我将ThemeRequested属性绑定到代理类Theme属性。

第二

创建您的光与暗的主题资源的App.xaml：

 <Application.Resources>
    <ResourceDictionary>
        <ResourceDictionary.MergedDictionaries>
            <ResourceDictionary>
                <ResourceDictionary.ThemeDictionaries>
                    <ResourceDictionary x:Key="Dark">
                        <SolidColorBrush x:Key="MyTextColor" Color="DarkGray" />
                    </ResourceDictionary>
                    <ResourceDictionary x:Key="Light">
                        <SolidColorBrush x:Key="MyTextColor" Color="White" />
                    </ResourceDictionary>
                </ResourceDictionary.ThemeDictionaries>
            </ResourceDictionary>
        </ResourceDictionary.MergedDictionaries>
    </ResourceDictionary>
</Application.Resources>

第三

在App.Xaml.cs中，将rootFrame更改为ThemeAwareFrame而不是简单的Frame：

rootFrame = new ThemeAwareFrame(ElementTheme.Dark);

在OnLaunched方法中：

     protected override void OnLaunched(LaunchActivatedEventArgs e)
     {
    #if DEBUG
        if (System.Diagnostics.Debugger.IsAttached)
        {
            this.DebugSettings.EnableFrameRateCounter = true;
        }
    #endif
        Frame rootFrame = Window.Current.Content as Frame;

        // Do not repeat app initialization when the Window already has content,
        // just ensure that the window is active
        if (rootFrame == null)
        {
            // Create a Frame to act as the navigation context and navigate to the first page
            rootFrame = new ThemeAwareFrame(ElementTheme.Dark);
            // TODO: change this value to a cache size that is appropriate for your application
            rootFrame.CacheSize = 1;

            if (e.PreviousExecutionState == ApplicationExecutionState.Terminated)
            {
                // TODO: Load state from previously suspended application
            }
     //..

向前

在使用与主题相关的资源时，请使用ThemeResource代替staticResource：

<Page.Resources>
    <Style x:Key="MyText" TargetType="TextBlock">
        <Setter Property="Foreground" Value="{ThemeResource MyTextColor}" />
    </Style>
</Page.Resources>

<Grid >
    <Grid.RowDefinitions>
        <RowDefinition Height="*"/>
        <RowDefinition Height="Auto"/>
        <RowDefinition Height="Auto"/>
    </Grid.RowDefinitions>
    <TextBlock Text="Test" Style="{StaticResource MyText}" VerticalAlignment="Center" HorizontalAlignment="Center"/>
    <Button Content="Dark Theme" Click="ChangeThemeToDarkClick" Grid.Row="1"></Button>
    <Button Content="Light Theme" Click="ChangeThemeToLightClick" Grid.Row="2"></Button>
</Grid>

最后

要更改您的应用主题，只需更改AppThemerootFrame的属性，如下所示：

   private void ChangeThemeToLightClick(object sender, RoutedEventArgs e)
    {
        (Window.Current.Content as ThemeAwareFrame).AppTheme = ElementTheme.Light;
    }

    private void ChangeThemeToDarkClick(object sender, RoutedEventArgs e)
    {
        (Window.Current.Content as ThemeAwareFrame).AppTheme = ElementTheme.Dark;
    }