如何为WinUI 3 Window设置Mica等系统背景效果

你之前的代码写法有误，WinUI 3 中设置系统背景需要配合 SystemBackdropConfiguration 配置窗口状态，同时绑定窗口激活、主题变化等事件，才能让背景正常生效。以下是支持 Mica、Mica Alt、Acrylic 三种背景的通用实现方案：

前提准备 #

• 确保项目目标 Windows 版本为 Windows 10 22H2（10.0.22621.0） 及以上（Mica Alt 等效果需该版本支持）
• 已安装 Microsoft.UI.Xaml.Media NuGet 包
• 在窗口 XAML 中将背景设为透明：<Window ... Background="Transparent">

代码实现 #

在你的窗口类中添加以下字段和方法：

1. 声明控制器字段 #

private MicaController? _micaController;
private MicaController? _micaAltController;
private DesktopAcrylicController? _acrylicController;

2. 设置 Mica 背景 #

private void SetMicaBackdrop()
{
    var backdropConfig = new SystemBackdropConfiguration();
    // 初始激活状态
    backdropConfig.IsInputActive = true;
    // 同步窗口主题
    backdropConfig.Theme = (Content as FrameworkElement)?.ActualTheme switch
    {
        ElementTheme.Dark => SystemBackdropTheme.Dark,
        ElementTheme.Light => SystemBackdropTheme.Light,
        _ => SystemBackdropTheme.Default
    };

    // 监听窗口激活状态变化
    Activated += (s, e) => 
        backdropConfig.IsInputActive = e.WindowActivationState != WindowActivationState.Deactivated;
    // 窗口关闭时释放控制器资源
    Closed += (s, e) => _micaController?.Dispose();

    _micaController = new MicaController();
    _micaController.AddSystemBackdropTarget(this);
    _micaController.SetSystemBackdropConfiguration(backdropConfig);
}

3. 设置 Mica Alt 背景 #

仅需修改控制器的 Kind 参数，其余逻辑和 Mica 一致：

private void SetMicaAltBackdrop()
{
    var backdropConfig = new SystemBackdropConfiguration();
    backdropConfig.IsInputActive = true;
    backdropConfig.Theme = (Content as FrameworkElement)?.ActualTheme switch
    {
        ElementTheme.Dark => SystemBackdropTheme.Dark,
        ElementTheme.Light => SystemBackdropTheme.Light,
        _ => SystemBackdropTheme.Default
    };

    Activated += (s, e) => 
        backdropConfig.IsInputActive = e.WindowActivationState != WindowActivationState.Deactivated;
    Closed += (s, e) => _micaAltController?.Dispose();

    _micaAltController = new MicaController { Kind = MicaKind.BaseAlt };
    _micaAltController.AddSystemBackdropTarget(this);
    _micaAltController.SetSystemBackdropConfiguration(backdropConfig);
}

4. 设置 Acrylic 背景 #

使用 DesktopAcrylicController 实现：

private void SetAcrylicBackdrop()
{
    var backdropConfig = new SystemBackdropConfiguration();
    backdropConfig.IsInputActive = true;
    backdropConfig.Theme = (Content as FrameworkElement)?.ActualTheme switch
    {
        ElementTheme.Dark => SystemBackdropTheme.Dark,
        ElementTheme.Light => SystemBackdropTheme.Light,
        _ => SystemBackdropTheme.Default
    };

    Activated += (s, e) => 
        backdropConfig.IsInputActive = e.WindowActivationState != WindowActivationState.Deactivated;
    Closed += (s, e) => _acrylicController?.Dispose();

    _acrylicController = new DesktopAcrylicController();
    _acrylicController.AddSystemBackdropTarget(this);
    _acrylicController.SetSystemBackdropConfiguration(backdropConfig);
}

调用方法 #

在窗口构造函数的 InitializeComponent() 之后，调用对应方法即可：

public MainWindow()
{
    InitializeComponent();
    // 按需选择一种背景
    SetMicaBackdrop();
    // SetMicaAltBackdrop();
    // SetAcrylicBackdrop();
}

注意事项 #

• 如果是非打包（Unpackaged）应用，需在 Program.cs 中确保已初始化 Windows App SDK：

  using Microsoft.UI.Xaml;
  
  namespace YourAppName;
  
  public partial class Program
  {
      [STAThread]
      static void Main(string[] args)
      {
          WinRT.ComWrappersSupport.InitializeComWrappers();
          Application.Start(p => new App());
      }
  }
  

• 若背景仍不生效，检查窗口是否有其他不透明元素覆盖了整个窗口区域。

内容的提问来源于stack exchange，提问作者user21603351