Xamarin Forms FlyOut菜单不会在ContentViews上显示，除非通过菜单访问

<Shell xmlns="http://xamarin.com/schemas/2014/forms"
       xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
       xmlns:local="clr-namespace:YourAppNamespace"
       FlyoutBehavior="Flyout"
       FlyoutIcon="hamburger.png">

    <FlyoutItem Title="Home" Icon="home.png">
        <ShellContent ContentTemplate="{DataTemplate local:HomePage}" />
    </FlyoutItem>

    <FlyoutItem Title="About" Icon="info.png">
        <ShellContent ContentTemplate="{DataTemplate local:AboutPage}" />
    </FlyoutItem>

    <!-- 添加其他菜单项 -->

</Shell>

public partial class HomePage : ContentPage
{
    public ICommand ShowMenuCommand { get; private set; }

    public HomePage()
    {
        InitializeComponent();

        ShowMenuCommand = new Command(() =>
        {
            // 显示FlyOut菜单
            Shell.Current.FlyoutIsPresented = true;
        });

        BindingContext = this;
    }
}