Building a Windows 8 Metro App, Part 3: Listing 8

Updated MainPage.xaml.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Windows.Foundation;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Data;
using VSMWinRTDemo.RSS;
using Windows.Storage;
using Windows.ApplicationModel.DataTransfer;
using VSMWinRTDemo.Storage;

namespace VSMWinRTDemo.UI
{
    partial class MainPage
    {
        private int _maxFeeds = 20;
        private RSSClient _client = new RSSClient();
        private DataTransferManager _dataTransferManager;
        const string DEFAULT_FEED_KEY = "DefaultFeedUri";
        const string MAX_FEED_ITEMS_KEY = "MaxFeedItems";

        public MainPage()
        {
            InitializeComponent();
            Loaded += new RoutedEventHandler(MainPage_Loaded);
            FeedListView.SelectionChanged += new SelectionChangedEventHandler(FeedListView_SelectionChanged);
            FetchButton.Click += new RoutedEventHandler(FetchButton_Click);
            _dataTransferManager = DataTransferManager.GetForCurrentView();
            _dataTransferManager.DataRequested += new TypedEventHandler<DataTransferManager, 
            DataRequestedEventArgs>(MainPage_DataRequested);
            NumFeeds.LostFocus += new RoutedEventHandler(NumFeeds_LostFocus);
        }

        void NumFeeds_LostFocus(object sender, RoutedEventArgs e)
        {
            if (!String.IsNullOrWhiteSpace(NumFeeds.Text))
            {
                _maxFeeds = int.Parse(NumFeeds.Text);
                SettingsStorage.SetLocalSetting(MAX_FEED_ITEMS_KEY, _maxFeeds);
            }
        }

        void MainPage_DataRequested(DataTransferManager sender, DataRequestedEventArgs args)
        {
            // have a selected RSS feed item?
            if (FeedListView.SelectedItem != null)
            {
                RSSItem selectedItem = FeedListView.SelectedItem as RSSItem;
                args.Request.Data.Properties.Title = selectedItem.Title;
                args.Request.Data.Properties.Description = selectedItem.Description;
                args.Request.Data.SetText(selectedItem.Description);
                args.Request.Data.SetHtml(selectedItem.Description);

                if (selectedItem.Links.Count > 0)
                {
                    args.Request.Data.SetUri(selectedItem.Links[0].Link);
                }
            }
            else if (!String.IsNullOrWhiteSpace(FeedUrl.Text))
            {
                // share the loaded Feed URL
                args.Request.Data.Properties.Title = FeedTitle.Text;
                args.Request.Data.Properties.Description = "An RSS feed link from Daily Reader.";
                args.Request.Data.SetUri(new Uri(FeedUrl.Text));
            }
        }

        void FeedListView_SelectionChanged(object sender, SelectionChangedEventArgs e)
        {
            ListView rssFeeds = (sender as ListView);
            RSSItem selectedItem = rssFeeds.SelectedItem as RSSItem;

            if (selectedItem != null && selectedItem.Links.Count > 0)
            {
                RSSItemWebView.Navigate(selectedItem.Links[0].Link);
            }
        }

        async void MainPage_Loaded(object sender, RoutedEventArgs e)
        {
            // load local settings
            string defaultFeedUri = SettingsStorage.GetLocalSetting<string>(DEFAULT_FEED_KEY);
            int maxFeeds = SettingsStorage.GetLocalSetting<int>(MAX_FEED_ITEMS_KEY);

            if (maxFeeds > 0)
            {
                _maxFeeds = maxFeeds;
            }

            NumFeeds.Text = _maxFeeds.ToString();

            if (defaultFeedUri != null)
            {
                FeedUrl.Text = defaultFeedUri;
                await GetFeeds(defaultFeedUri);
            }
        }

        private async void FetchButton_Click(object sender, RoutedEventArgs e)
        {
            if (!String.IsNullOrWhiteSpace(FeedUrl.Text))
            {
                await GetFeeds(FeedUrl.Text);
            }
        }

        private async Task GetFeeds(string url)
        {
            RSSFeed feeds = null;

            if (LocalStorage.ContainsItem(url))
            {
                feeds = LocalStorage.GetItem<RSSFeed>(url);
                Cached.Visibility = Windows.UI.Xaml.Visibility.Visible;
            }
            else
            {
                Cached.Visibility = Windows.UI.Xaml.Visibility.Collapsed;
                feeds = await _client.GetFeeds(url, _maxFeeds);
            }

            BindFeeds(feeds, url);
        }

        private void BindFeeds(RSSFeed feeds, string url)
        {
            this.DataContext = feeds;
            LocalStorage.Data[url] = feeds;
        }

        private void SetDefaultButton_Click(object sender, RoutedEventArgs e)
        {
            SettingsStorage.SetLocalSetting(DEFAULT_FEED_KEY, FeedUrl.Text);
        }
    }
}

About the Author

Eric Vogel is a Senior Software Developer for Red Cedar Solutions Group in Okemos, Michigan. He is the president of the Greater Lansing User Group for .NET. Eric enjoys learning about software architecture and craftsmanship, and is always looking for ways to create more robust and testable applications. Contact him at vogelvision@gmail.com.