NavigationPage 流程

using System;
using Xamarin.Forms;

namespace NavigationApp
{    
    public class App : Application
    {
        public App()
        {
            MainPage = new NavigationPage(new FirstPage());
        }
    }

    public class FirstPage : ContentPage
    {
        Label FirstPageLabel { get; set; } = new Label();

        Button FirstPageButton { get; set; } = new Button();

        public FirstPage()
        {
            Title = "First page";

            FirstPageLabel.Text = "This is the first page";
            FirstPageButton.Text = "Navigate to the second page";
            FirstPageButton.Clicked += OnFirstPageButtonClicked;

            var content = new StackLayout();
            content.Children.Add(FirstPageLabel);
            content.Children.Add(FirstPageButton);

            Content = content;
        }

        async void OnFirstPageButtonClicked(object sender, EventArgs e)
        {
            await Navigation.PushAsync(new SecondPage(), true);
        }
    }

    public class SecondPage : ContentPage
    {
        Label SecondPageLabel { get; set; } = new Label();

        public SecondPage()
        {
            Title = "Second page";

            SecondPageLabel.Text = "This is the second page";

            Content = SecondPageLabel;
        }
    }
}