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 Foundation;
using 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
    {

        /// <summary>
        /// Choose a feed from https://rss.itunes.apple.com/
        /// </summary>
		static readonly Uri RssFeedUrl = new Uri("https://rss.itunes.apple.com/api/v1/us/ios-apps/top-free/all/50/non-explicit.atom");


        UINavigationController NavigationController { get; set; }

        RootViewController RootController { get; set; }

        public override 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 application, NSDictionary launchOptions)
        {
            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();
        }
    }
}