如何在Xamarin窗体中关闭初始屏幕之前显示确认对话框

using Xamarin.Forms;

public class MainPage : ContentPage
{
    public MainPage()
    {
        var closeButton = new Button { Text = "Close" };
        closeButton.Clicked += async (sender, e) =>
        {
            bool confirmed = await DisplayAlert("Confirm", "Are you sure you want to close?", "Yes", "No");
            if (confirmed)
            {
                // 用户点击了 "Yes"，可以在这里执行关闭操作
                Application.Current.MainPage = new NavigationPage(new AnotherPage());
            }
        };

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

public class AnotherPage : ContentPage
{
    public AnotherPage()
    {
        Title = "Another Page";
        Content = new Label { Text = "Welcome to Another Page!" };
    }
}

Device.BeginInvokeOnMainThread(async () =>
{
    bool confirmed = await DisplayAlert("Confirm", "Are you sure?", "Yes", "No");
    if (confirmed)
    {
        // 用户确认后的操作
    }
});