자마린 스튜디오(Xamarin Studio)에서 비동기로 이미지 받아오기

이미지의 경우 속도가 느리기 때문에 대부분 비동기 형태로 웹서버에서 받아와야 합니다.

iOS의 경우 GCD를 제공합니다. 닷넷의 경우 await/async를 결합해서 보다 쉽게 사용할 수 있습니다.

<?xml version="1.0" encoding="utf-8"?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms" xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml" xmlns:local="clr-namespace:DemoBacktoWeb" x:Class="DemoBacktoWeb.DemoBacktoWebPage">

     <ContentPage.Padding>
         <OnPlatform x:TypeArguments="Thickness"
             iOS="0, 20, 0, 0" />
        </ContentPage.Padding>
    
      <StackLayout>
         <Grid VerticalOptions="FillAndExpand">
             <Label x:Name="errorLabel"
                 HorizontalOptions="Center"
                 VerticalOptions="Center" />
             <ActivityIndicator IsRunning="{Binding Source={x:Reference image},
                 Path=IsLoading}" />
             <Image x:Name="image" />
         </Grid>
        
         <Button Text="Load Bitmap"
             HorizontalOptions="Center"
             Clicked="OnLoadButtonClicked" />
     </StackLayout>
</ContentPage>

using System.Net;

namespace DemoBacktoWeb
{
    public partial class DemoBacktoWebPage : ContentPage
    {
        public DemoBacktoWebPage()
        {
            InitializeComponent();
        }

        async void OnLoadButtonClicked(object sender, EventArgs args)
        {
            try
            {
                Stream stream =
                    await GetStreamAsync("https://developer.xamarin.com/demo/IMG_1996.JPG");
                image.Source = ImageSource.FromStream(() => stream);
            }
            catch (Exception exc)
            {
                errorLabel.Text = exc.Message;
            }
        }

        async Task<Stream> GetStreamAsync(string uri)
        {
            TaskFactory factory = new TaskFactory();
            WebRequest request = WebRequest.Create(uri);
            WebResponse response = await factory.FromAsync<WebResponse>(request.BeginGetResponse,
                                                                        request.EndGetResponse, null);
            return response.GetResponseStream(); 
        }
    }
}