如何实现Android开发中弹出菜单的效果

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

namespace ch05demos.SrcActivity
{
  [Activity(Label = "Demo07PopupMenu")]
  public class Demo07PopupMenu : Activity
  {
    protected override void OnCreate(Bundle savedInstanceState)
    {
      base.OnCreate(savedInstanceState);
      SetContentView(Resource.Layout.demo07_Popup);

      Button btn = FindViewById(Resource.Id.popupButton);
      btn.Click += (s, arg) =>
      {
        PopupMenu menu = new PopupMenu(this, btn);
        menu.Inflate(Resource.Menu.demo07_popup_menu);
        menu.MenuItemClick += (sender, args) =>
        {
          string str = string.Format("你选择了：{0}", args.Item);
          Toast.MakeText(this,str, ToastLength.Short).Show();
        };
        menu.DismissEvent += (sender, args) =>
        {
          //菜单消失后可在此事件中做一些后续处理
        };
        menu.Show();
      };
    }
  }
}