Xamarin:如何在MasterDetailPage中显示菜单按钮

using Xamarin.Forms;

public class MainPage : MasterDetailPage
{
    public MainPage()
    {
        var menuPage = new NavigationPage(new MenuPage());
        var detailPage = new NavigationPage(new DetailPage());

        Master = menuPage;
        Detail = detailPage;

        menuPage.Title = "Menu";
        detailPage.Title = "Detail";

        menuPage.IconImageSource = "menu_icon.png";

        menuPage.ListView.ItemSelected += (sender, e) =>
        {
            if (e.SelectedItem is MenuItem menuItem)
            {
                Detail = new NavigationPage(menuItem.Page);
                IsPresented = false;
                menuPage.ListView.SelectedItem = null;
            }
        };
    }
}

public class MenuPage : ContentPage
{
    public ListView ListView { get; }

    public MenuPage()
    {
        Title = "Menu";

        ListView = new ListView
        {
            ItemsSource = new[]
            {
                new MenuItem { Title = "Page 1", Page = new Page1() },
                new MenuItem { Title = "Page 2", Page = new Page2() },
                // 添加更多菜单项...
            },
            ItemTemplate = new DataTemplate(typeof(TextCell))
        };

        Content = new StackLayout
        {
            Children = { ListView }
        };
    }
}

public class DetailPage : ContentPage
{
    public DetailPage()
    {
        Title = "Detail";

        Content = new Label
        {
            Text = "This is the detail page."
        };
    }
}

public class MenuItem
{
    public string Title { get; set; }
    public Page Page { get; set; }
}

public class Page1 : ContentPage
{
    public Page1()
    {
        Title = "Page 1";

        Content = new Label
        {
            Text = "This is Page 1."
        };
    }
}

public class Page2 : ContentPage
{
    public Page2()
    {
        Title = "Page 2";

        Content = new Label
        {
            Text = "This is Page 2."
        };
    }
}