有没有办法让 WPF 应用程序尊重 Windows 10 中深色/浅色主题的系统选择？

Windows 10最近添加了深色模式；有什么方法可以让我的 WPF 应用程序尊重此设置吗？最好是一个可以自动翻转它的开关，但如果没有，我想我可以在某处读取系统设置并切换到我的代码或其他东西中的备用主题......

没有直接的 API/事件来检测 wpf 的暗模式或高对比度模式。可以在 uwp 中找到。但是有一种方法可以通过 WMI 查询来检测主题更改事件，以观察相关注册表项的注册表更改。你会发现详情here https://engy.us/blog/2018/10/20/dark-theme-in-wpf/。 我有一个简化的类，您可以通过它检测注册表更改。

public class ThemeWatcher
{
    private const string RegistryKeyPath = @"Software\Microsoft\Windows\CurrentVersion\Themes\Personalize";

    private const string RegistryValueName = "AppsUseLightTheme";
    private static WindowsTheme windowsTheme;

    public WindowsTheme WindowsTheme
    {
        get { return windowsTheme; }
        set { windowsTheme = value; }
    }

    public void StartThemeWatching()
    {
        var currentUser = WindowsIdentity.GetCurrent();
        string query = string.Format(
            CultureInfo.InvariantCulture,
            @"SELECT * FROM RegistryValueChangeEvent WHERE Hive = 'HKEY_USERS' AND KeyPath = '{0}\\{1}' AND ValueName = '{2}'",
            currentUser.User.Value,
            RegistryKeyPath.Replace(@"\", @"\\"),
            RegistryValueName);
        
        try
        {
            windowsTheme = GetWindowsTheme();
            MergeThemeDictionaries(windowsTheme);

            var watcher = new ManagementEventWatcher(query);
            watcher.EventArrived += Watcher_EventArrived;
            SystemParameters.StaticPropertyChanged += SystemParameters_StaticPropertyChanged;
            // Start listening for events
            watcher.Start();
        }
        catch (Exception ex)
        {
            // This can fail on Windows 7
            windowsTheme = WindowsTheme.Default;
            
        }

    }

    private void MergeThemeDictionaries(WindowsTheme windowsTheme)
    {
        string appTheme = "Light";
        switch (windowsTheme)
        {
            case WindowsTheme.Light:
                appTheme = "Light";
                break;
            case WindowsTheme.Dark:
                appTheme = "Dark";
                break;
            case WindowsTheme.HighContrast:
                appTheme = "HighContrast";
                break;
        }

        App.Current.Resources.MergedDictionaries[0].Source = new Uri($"/Themes/{appTheme}.xaml", UriKind.Relative);
        
    }

    private void SystemParameters_StaticPropertyChanged(object sender, System.ComponentModel.PropertyChangedEventArgs e)
    {
        windowsTheme = GetWindowsTheme();

        MergeThemeDictionaries(windowsTheme);

        ThemeChangedArgument themeChangedArgument = new ThemeChangedArgument();
        themeChangedArgument.WindowsTheme = windowsTheme;

        App.WindowsThemeChanged?.Invoke(this, themeChangedArgument);
        
    }

    private void Watcher_EventArrived(object sender, EventArrivedEventArgs e)
    {
        windowsTheme = GetWindowsTheme();

        MergeThemeDictionaries(windowsTheme);

        ThemeChangedArgument themeChangedArgument = new ThemeChangedArgument();
        themeChangedArgument.WindowsTheme = windowsTheme;

        App.WindowsThemeChanged?.Invoke(this, themeChangedArgument);
        
    }

    public WindowsTheme GetWindowsTheme()
    {
        WindowsTheme theme = WindowsTheme.Light;

        try
        {
            using (RegistryKey key = Registry.CurrentUser.OpenSubKey(RegistryKeyPath))
            {
                object registryValueObject = key?.GetValue(RegistryValueName);
                if (registryValueObject == null)
                {
                    return WindowsTheme.Light;
                }

                int registryValue = (int)registryValueObject;

                if (SystemParameters.HighContrast)
                    theme = WindowsTheme.HighContrast;

                theme = registryValue > 0 ? WindowsTheme.Light : WindowsTheme.Dark;
            }

            return theme;
        }
        catch (Exception ex)
        {
            return theme;
        }
    }
}

创建相关的Enum进行逻辑实现：

public enum WindowsTheme
{
    Default = 0,
    Light = 1,
    Dark = 2,
    HighContrast = 3
}

将相关资源文件添加到项目中。

定义一个回调参数，当注册表发生更改时，该参数将通过事件处理程序传递。

public class ThemeChangedArgument
{
    public WindowsTheme WindowsTheme { set; get; }
}

现在开始观看从 App.xaml.cs 的 OnStartup 方法更改的主题。

public partial class App : Application
{
  private ThemeWatcher themeWatcher;
  private WindowsTheme systrayTheme = WindowsTheme.Light;
  public static EventHandler<ThemeChangedArgument> WindowsThemeChanged;
  .......

   protected override void OnStartup(StartupEventArgs e)
   {
   .......................
    themeWatcher = new ThemeWatcher();
    systrayTheme = themeWatcher.GetWindowsTheme();
    themeWatcher.StartThemeWatching();

    if(WindowsThemeChanged != null)
    {
        WindowsThemeChanged -= OnWindowsThemeChanged;
    }

    WindowsThemeChanged += OnWindowsThemeChanged;
    .......................
   }

  private void OnWindowsThemeChanged(object sender, ThemeChangedArgument e)
  {
    systrayTheme = e.WindowsTheme;
    //Now do whatever you want to do with this updated theme.
  }
  
        
    protected override void OnExit(ExitEventArgs e)
    {
        base.OnExit(e);

        try
        {
            if (WindowsThemeChanged != null)
            {
                WindowsThemeChanged -= OnWindowsThemeChanged;
            }
            Application.Current?.Shutdown();
            Process.GetCurrentProcess()?.Kill();
        }
        catch (Exception ex)
        {
        
        }
    }

}

注意：我们已经将 ThemeWatcher 类中的相关样式资源与该方法合并合并主题字典()由于主题更改事件被触发。您也可以根据您的需要从这里更新它。

由于运行时资源发生变化后，调用以下方法来更新 UI。

    private void InvalidedMainWindow()
    {
        if (!Application.Current.Dispatcher.CheckAccess())
        {
            Application.Current.Dispatcher.InvokeAsync(() => InvalidedMainWindow());
            return;
        }

        App.Current.MainWindow.UpdateLayout();
    }