Windows平台MAUI：如何隐藏或覆盖WinUI3灰色伪标题栏？

针对你恢复Win32原生标题栏后，WinUI3灰色伪标题栏残留导致双标题栏的问题，以下是几种仅适配Windows 10的可行方案：

方案1：直接隐藏WinUI伪标题栏元素 #

WinUI3添加的灰色伪标题栏本质是Shell根视图内的一个顶部容器，可通过定位并隐藏该元素彻底解决问题：

// 在MAUI Windows平台项目的初始化代码中（如App.xaml.cs的OnLaunched方法）
var mauiWindow = MauiWinUIApplication.Current.Windows[0];
var winuiWindow = mauiWindow.Handler.PlatformView as Microsoft.UI.Xaml.Window;
var rootFrame = winuiWindow.Content as Microsoft.UI.Xaml.Controls.Frame;

if (rootFrame?.Content is Microsoft.UI.Xaml.Controls.Page page)
{
    if (page.Content is Microsoft.Maui.Controls.Platform.ShellRenderer.ShellRootView shellRoot)
    {
        // 遍历子元素找到WinUI伪标题栏（默认高度32）
        foreach (var child in shellRoot.Children)
        {
            if (child is Microsoft.UI.Xaml.Controls.Border titleBarBorder && 
                Math.Abs(titleBarBorder.ActualHeight - 32) < 1)
            {
                titleBarBorder.Visibility = Microsoft.UI.Xaml.Visibility.Collapsed;
                break;
            }
        }
    }
}

如果无法准确定位元素，也可以直接通过负边距将伪标题栏顶出可视区域：

shellRoot.Margin = new Microsoft.UI.Xaml.Thickness(0, -32, 0, 0);

方案2：通过Shell布局覆盖伪标题栏 #

若希望保留Shell导航栏的自定义样式，可调整Shell的内边距和背景色，让导航栏直接覆盖WinUI伪标题栏：

1. 修改AppShell.xaml #

<Shell xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
       xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
       x:Class="YourAppNamespace.AppShell"
       NavigationBarBackgroundColor="Transparent"
       BackgroundColor="Transparent">

    <!-- 设置页面内容的顶部内边距，避开原生标题栏 -->
    <Shell.ItemTemplate>
        <DataTemplate>
            <Grid Margin="0,32,0,0">
                <!-- 页面内容 -->
            </Grid>
        </DataTemplate>
    </Shell.ItemTemplate>

    <!-- 你的Shell路由定义 -->
</Shell>

2. 适配Windows平台Shell样式 #

// 在Windows平台项目的Platforms/Windows/App.xaml.cs中
using Microsoft.Maui.Handlers;

public partial class App : MauiWinUIApplication
{
    protected override void OnLaunched(LaunchActivatedEventArgs args)
    {
        base.OnLaunched(args);

        // 移除Shell默认的顶部内边距，确保导航栏覆盖伪标题栏
        ShellHandler.Mapper.AppendToMapping("OverrideTitleBarPadding", (handler, view) =>
        {
            var platformShell = handler.PlatformView;
            platformShell.Padding = new Microsoft.UI.Xaml.Thickness(0);
            platformShell.Margin = new Microsoft.UI.Xaml.Thickness(0);
        });
    }
}

方案3：优化Win32标题栏同步（辅助） #

配合你之前拦截WM_NCCALCSIZE的逻辑，可添加对WM_DWMCOLORIZATIONCOLORCHANGED消息的处理，确保原生标题栏颜色跟随系统强调色实时更新：

// 在Win32窗口子类的WndProc方法中添加
private const int WM_DWMCOLORIZATIONCOLORCHANGED = 0x0320;
private const uint RDW_FRAME = 0x0040;
private const uint RDW_INVALIDATE = 0x0001;

[DllImport("dwmapi.dll")]
private static extern void DwmInvalidateIconicBitmaps(IntPtr hwnd);

protected override IntPtr WndProc(IntPtr hwnd, int msg, IntPtr wParam, IntPtr lParam, ref bool handled)
{
    switch (msg)
    {
        case WM_DWMCOLORIZATIONCOLORCHANGED:
            // 刷新非客户区，同步标题栏颜色
            DwmInvalidateIconicBitmaps(hwnd);
            RedrawWindow(hwnd, IntPtr.Zero, IntPtr.Zero, RDW_FRAME | RDW_INVALIDATE);
            handled = false;
            break;
        // 你的WM_NCCALCSIZE处理逻辑
    }
    return base.WndProc(hwnd, msg, wParam, lParam, ref handled);
}

内容的提问来源于stack exchange，提问作者Medinoc