Xamarin C#：在水平LinearLayout中垂直居中

using Android.App;
using Android.OS;
using Android.Widget;

namespace XamarinApp
{
    [Activity(Label = "XamarinApp", MainLauncher = true)]
    public class MainActivity : Activity
    {
        protected override void OnCreate(Bundle savedInstanceState)
        {
            base.OnCreate(savedInstanceState);
            SetContentView(Resource.Layout.Main);

            var horizontalLayout = FindViewById<LinearLayout>(Resource.Id.horizontalLayout);
            var verticalLayout = new LinearLayout(this);
            verticalLayout.Orientation = Orientation.Vertical;
            verticalLayout.Gravity = GravityFlags.Center;

            var textView = new TextView(this);
            textView.Text = "居中文本";
            textView.Gravity = GravityFlags.Center;

            verticalLayout.AddView(textView);
            horizontalLayout.AddView(verticalLayout);
        }
    }
}