Windows MAUI窗口最大化无法铺满顶部问题求助

问题现象 #

在.NET MAUI 8.0.0-preview4中实现窗口完全最大化时，原标题栏位置仍留有空白栏（红色为页面内容，黑色为残留的标题栏区域）：

通过修改MAUI模板，用“Click me”按钮切换窗口最大化状态，代码如下：

private void OnCounterClicked(object sender, EventArgs e)
{
    var window = Window.Handler.PlatformView as MauiWinUIWindow;
    var handle = WinRT.Interop.WindowNative.GetWindowHandle(window);
    var id = Microsoft.UI.Win32Interop.GetWindowIdFromWindow(handle);
    var appWindow = Microsoft.UI.Windowing.AppWindow.GetFromWindowId(id);

    switch (appWindow.Presenter)
    {
        case Microsoft.UI.Windowing.OverlappedPresenter overlappedPresenter:
            if (overlappedPresenter.State == Microsoft.UI.Windowing.OverlappedPresenterState.Maximized)
            {
                overlappedPresenter.SetBorderAndTitleBar(true, true);
                overlappedPresenter.Restore();
            }
            else
            {
                overlappedPresenter.SetBorderAndTitleBar(false, false);
                overlappedPresenter.Maximize();
            }

            break;
    }
}

已移除Shell，直接使用MainPage，但SetBorderAndTitleBar仅移除标题栏按钮，未真正消除标题栏空白，无法实现真正的全屏体验。

解决方法 #

1. 调整窗口扩展区域与布局边距 #

修改点击事件代码，结合TitleBar.ExtendsContentIntoTitleBar和设置标题栏高度，同时调整MAUI窗口内容边距：

private void OnCounterClicked(object sender, EventArgs e)
{
    var window = Window.Handler.PlatformView as MauiWinUIWindow;
    var handle = WinRT.Interop.WindowNative.GetWindowHandle(window);
    var id = Microsoft.UI.Win32Interop.GetWindowIdFromWindow(handle);
    var appWindow = Microsoft.UI.Windowing.AppWindow.GetFromWindowId(id);

    switch (appWindow.Presenter)
    {
        case Microsoft.UI.Windowing.OverlappedPresenter overlappedPresenter:
            if (overlappedPresenter.State == Microsoft.UI.Windowing.OverlappedPresenterState.Maximized)
            {
                // 恢复窗口时还原标题栏设置
                overlappedPresenter.SetBorderAndTitleBar(true, true);
                var titleBar = appWindow.TitleBar;
                titleBar.ExtendsContentIntoTitleBar = false;
                overlappedPresenter.Restore();
                window.ContentRoot.Margin = new Microsoft.UI.Xaml.Thickness(0);
            }
            else
            {
                // 最大化时隐藏边框和标题栏，让内容延伸覆盖原标题栏区域
                overlappedPresenter.SetBorderAndTitleBar(false, false);
                var titleBar = appWindow.TitleBar;
                titleBar.ExtendsContentIntoTitleBar = true;
                titleBar.Height = 0;
                overlappedPresenter.Maximize();
                window.ContentRoot.Margin = new Microsoft.UI.Xaml.Thickness(0);
            }
            break;
    }
}

2. 确保页面无默认边距 #

检查MainPage的XAML，移除默认的Padding和Margin，确保内容铺满窗口：

<ContentPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             x:Class="MaximizeMaui.MainPage"
             Padding="0" Margin="0">
    <!-- 页面内容 -->
</ContentPage>

3. 可选：使用全屏演示者实现彻底全屏 #

如果需要覆盖任务栏的完全全屏效果，可切换到FullScreenPresenter：

private void OnCounterClicked(object sender, EventArgs e)
{
    var window = Window.Handler.PlatformView as MauiWinUIWindow;
    var handle = WinRT.Interop.WindowNative.GetWindowHandle(window);
    var id = Microsoft.UI.Win32Interop.GetWindowIdFromWindow(handle);
    var appWindow = Microsoft.UI.Windowing.AppWindow.GetFromWindowId(id);

    if (appWindow.Presenter.Kind == Microsoft.UI.Windowing.AppWindowPresenterKind.FullScreen)
    {
        // 退出全屏，还原为普通窗口
        appWindow.SetPresenter(Microsoft.UI.Windowing.AppWindowPresenterKind.Overlapped);
        var overlappedPresenter = (Microsoft.UI.Windowing.OverlappedPresenter)appWindow.Presenter;
        overlappedPresenter.SetBorderAndTitleBar(true, true);
        var titleBar = appWindow.TitleBar;
        titleBar.ExtendsContentIntoTitleBar = false;
    }
    else
    {
        // 切换到全屏模式
        appWindow.SetPresenter(Microsoft.UI.Windowing.AppWindowPresenterKind.FullScreen);
    }
}

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