主细节根页面

public class App : Application
{
    internal static NavigationPage NavPage;

    public App ()
    {
        // The root page of your application
        MainPage = new RootPage();
    }
}
public class RootPage : MasterDetailPage
{
    public RootPage()
    {
        var menuPage = new MenuPage();
        menuPage.Menu.ItemSelected += (sender, e) => NavigateTo(e.SelectedItem as MenuItem);
        Master = menuPage;
        App.NavPage = new NavigationPage(new HomePage());
        Detail = App.NavPage;
    }
    protected override async void OnAppearing()
    {
        base.OnAppearing();
    }
    void NavigateTo(MenuItem menuItem)
    {
        Page displayPage = (Page)Activator.CreateInstance(menuItem.TargetType);
        Detail = new NavigationPage(displayPage);
        IsPresented = false;
    }
}