我在主详细信息页面中没有看到 "back" 箭头

I do not get the "back" arrow in Master Detail Page

使用主从页面的标准(模板)实现,调用侧边菜单时没有后退按钮。 标准实现如下所示:

<NavigationPage>
            <x:Arguments>
                <local:DetailPage1/>
            </x:Arguments>
</NavigationPage>

但是当我这样实现导航时:

MainPage = new NavigationPage(new MainPage());

我拿回了按钮

为什么会发生这种情况,为什么我没有获得标准(模板)实现的按钮?谢谢

底部带有 运行 按钮的屏幕截图

enter image description here

首先 - 菜单(母版页)不应该有后退按钮。

来自official documentation

A MasterDetailPage is designed to be a root page, and using it as a child page in other page types could result in unexpected and inconsistent behavior. In addition, it's recommended that the master page of a MasterDetailPage should always be a ContentPage instance, and that the detail page should only be populated with TabbedPage, NavigationPage, and ContentPage instances. This will help to ensure a consistent user experience across all platforms.

如果您的 MasterDetailPage 不是根页面并且被 NavigationPage 包裹,您可能会看到后退箭头。

这应该可以回答您的问题。
same official doc 中列出了其他详细信息和限制。