ios-samples/LazyTableImages/AppDelegate.cs

// 
// AppDelegate.cs
//  
// Author:
//       Alan McGovern <alan@xamarin.com>
// 
// Copyright 2011, Xamarin Inc.
// 
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
// 
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.

using System;
using System.Collections.Generic;
using System.Linq;
using MonoTouch.Foundation;
using MonoTouch.UIKit;
using System.Net;
using System.Collections.ObjectModel;

namespace LazyTableImages {
	/// <summary>
	/// The UIApplicationDelegate for the application. This class is responsible for launching the 
	/// User Interface of the application, as well as listening (and optionally responding) to 
	/// application events from iOS.
	/// </summary>

	[Register ("AppDelegate")]
	public partial class AppDelegate : UIApplicationDelegate {
		
		static readonly Uri RssFeedUrl = new Uri ("http://phobos.apple.com/WebObjects/MZStoreServices.woa/ws/RSS/toppaidapplications/limit=75/xml");
		
		UINavigationController NavigationController { get; set; }
		
		RootViewController RootController { get; set; }
		
		public UIWindow Window { get; set; }
		
		
		/// <summary>
		/// This method is invoked when the application has loaded and is ready to run. In this 
		/// method you should instantiate the window, load the UI into it and then make the window
		/// visible.
		/// </summary>
		/// <remarks>
		/// You have 5 seconds to return from this method, or iOS will terminate your application.
		/// </remarks>
		public override bool FinishedLaunching (UIApplication app, NSDictionary options)
		{
			Window = new UIWindow (UIScreen.MainScreen.Bounds);
			RootController = new RootViewController ("RootViewController", null);
			NavigationController = new UINavigationController (RootController);
			Window.RootViewController = NavigationController;
			
			// make the window visible
			Window.MakeKeyAndVisible ();
			
			BeginDownloading ();
			return true;
		}
		
		void BeginDownloading ()
		{
			// Show the user that data is about to be downloaded
			UIApplication.SharedApplication.NetworkActivityIndicatorVisible = true;
			
			// Retrieve the rss feed from the server
			var downloader = new GzipWebClient ();
			downloader.DownloadStringCompleted += DownloadCompleted;
			downloader.DownloadStringAsync (RssFeedUrl);
		}

		void DownloadCompleted (object sender, DownloadStringCompletedEventArgs e)
		{
			// The WebClient will invoke the DownloadStringCompleted event on a
			// background thread. We want to do UI updates with the result, so process
			// the result on the main thread.
			UIApplication.SharedApplication.BeginInvokeOnMainThread (() => {
				// First disable the download indicator
				UIApplication.SharedApplication.NetworkActivityIndicatorVisible = false;
				
				// Now handle the result from the WebClient
				if (e.Error != null) {
					DisplayError ("Warning", "The rss feed could not be downloaded: " + e.Error.Message);
				} else {
					try {
						RootController.Apps.Clear ();
						foreach (var v in RssParser.Parse (e.Result))
							RootController.Apps.Add (v);
					} catch {
						DisplayError ("Warning", "Malformed Xml was found in the Rss Feed.");
					}
				}
			});
		}
		
		void DisplayError (string title, string errorMessage, params object[] formatting)
		{
			var alert = new UIAlertView (title, string.Format (errorMessage, formatting), null, "ok", null);
			alert.Show ();
		}
	}
}