MainPage未添加到导航堆栈

Question

我只需调用以下命令即可启动Xamarin.Forms android项目：

    MainPage = new NavigationPage(new HomePage());

在App.xaml.cs中

如https://developer.xamarin.com/guides/xamarin-forms/application-fundamentals/navigation/hierarchical/中所述

这导致HomePage ContentPage实例被推入导航堆栈，在该堆栈中它成为应用程序的活动页面和根页面。

但是当我检查堆栈时，它是空的：

这是怎么回事 为什么页面不在堆栈中？

Answer 1

我只是创建了一个新的XF项目。

我已经将主页xml更改为此

<?xml version="1.0" encoding="utf-8"?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms" xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml" xmlns:local="clr-namespace:Test" x:Class="Test.TestPage">
    <StackLayout>
        <Button Text="How many?" Clicked="Handle_Clicked"/>
        <Label Text="Welcome to Xamarin Forms!" VerticalOptions="Center" HorizontalOptions="Center" />
    </StackLayout>
</ContentPage>

并将其添加到xml.cs

void Handle_Clicked(object sender, System.EventArgs e)
{
    //throw new NotImplementedException();
    Application.Current.MainPage.DisplayAlert("Attention", Navigation.NavigationStack.Count.ToString(), "Ok");
}

我看到NavigationStack的Count是1 ...

更新

同样对于CarouselPage，我有相同的结果

<?xml version="1.0" encoding="UTF-8"?>
<CarouselPage xmlns="http://xamarin.com/schemas/2014/forms" 
    xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml" 
    x:Class="Test.TestPage">
    <ContentPage>
        <StackLayout>
            <Button Text = "how many?" Clicked="Handle_Clicked"/>
            <Label Text="Red" />
            <BoxView Color="Red" VerticalOptions="FillAndExpand" />
        </StackLayout>
    </ContentPage>
    <ContentPage>
        <StackLayout>
            <Label Text="Green" />
            <BoxView Color="Green" VerticalOptions="FillAndExpand" />
        </StackLayout>
    </ContentPage>
    <ContentPage>
        <StackLayout>
            <Label Text="Blue" />
            <BoxView Color="Blue" VerticalOptions="FillAndExpand" />
        </StackLayout>
    </ContentPage>
</CarouselPage>