xamarin.Android ImageView 异步加载网络图片

 　　　　/// <summary>
        /// 异步获取文件流
        /// </summary>
        /// <param name="url"></param>
        /// <returns></returns>
        public async Task<Stream> GetFileStreamAsync(string url)
        {
            try
            {
                System.Net.Http.HttpClient client = new System.Net.Http.HttpClient();
                var fileStream = await client.GetStreamAsync(url);
                return fileStream;
            }
            catch (Exception ex)
            {
                throw new WebServiceException(ex.Message);
            }
        }

 　　　　private async void SetImage(string url)
        {var stream = await GetFileStreamAsync(url);
            var imageView = FindViewById<ImageView>(Resource.Id.iv_userphoto_mycenter_myprofile);
            imageView.SetImageBitmap(BitmapFactory.DecodeStream(stream));
        }