Mono for Android 显示远程图片

Main.axml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:background="#fff">
    <ImageView
        android:id="@+id/showPic"
        android:layout_width="400px"
        android:layout_height="400px" />
</LinearLayout>

MainActivity.cs

using System;
using System.IO;
using System.Net;
using Android.App;
using Android.Content;
using Android.Graphics.Drawables;
using Android.Runtime;
using Android.Views;
using Android.Widget;
using Android.OS;

namespace LoadPic
{
    [Activity(Label = "LoadPic", MainLauncher = true)]
    public class MainActivity : Activity
    {
        private ImageView showPic;
        private string picPath = "http://www.kl.cc/images/about/tizi/jiangkun/inscription-jiangkun.jpg";
        ProgressDialog msgbox;

        protected override void OnCreate(Bundle bundle)
        {
            base.OnCreate(bundle);
            SetContentView(Resource.Layout.Main);
            showPic = FindViewById<ImageView>(Resource.Id.showPic);
            msgbox = ProgressDialog.Show(this, "请稍等", "图片正在加载中...", true, true);
            HttpWebRequest req = WebRequest.Create(picPath) as HttpWebRequest;
            req.Method = "Get";
            req.GetResponseAsync().ContinueWith(o =>
            {
                HttpWebResponse resp = (HttpWebResponse)o.Result;
                this.RunOnUiThread(() =>
                {
                    Drawable dr = new BitmapDrawable(resp.GetResponseStream());
                    showPic.SetImageDrawable(dr);
                    msgbox.Cancel();
                });
            });
        }
    }
}