如何将按钮添加到标签上方的TabbedPage中

using Xamarin.Forms;

public class CustomTabbedPage : TabbedPage
{
    public CustomTabbedPage()
    {
        // 添加标签页
        Children.Add(new Page1());
        Children.Add(new Page2());

        // 创建按钮
        var button = new Button
        {
            Text = "按钮",
            HorizontalOptions = LayoutOptions.Center,
            VerticalOptions = LayoutOptions.Center
        };

        // 将按钮添加到标签页的上方
        var stackLayout = new StackLayout
        {
            Orientation = StackOrientation.Vertical,
            Children = { button, this }
        };

        // 设置标签页的内容视图为新的布局
        Content = stackLayout;
    }
}

using Xamarin.Forms;

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

        // 页面1的内容
        Content = new Label
        {
            Text = "这是页面1",
            HorizontalOptions = LayoutOptions.Center,
            VerticalOptions = LayoutOptions.Center
        };
    }
}

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

        // 页面2的内容
        Content = new Label
        {
            Text = "这是页面2",
            HorizontalOptions = LayoutOptions.Center,
            VerticalOptions = LayoutOptions.Center
        };
    }
}

using Xamarin.Forms;

public partial class App : Application
{
    public App()
    {
        InitializeComponent();

        MainPage = new CustomTabbedPage();
    }
}