/// <summary>
/// Retrieves feed data from the server and updates the appropriate FeedViewModel properties.
/// There may be two condition, One is for the Have ReFreshbuild and the orther is not.
/// </summary>
/// 已经修改了变量名使之可以编译，还没有全体check
private static async Task <bool> TryGetFeedFromServerAsync(FeedViewModel feedViewModel, CancellationToken?cancellationToken = null)
{
var originalArticleNum = feedViewModel.Articles.Count;
try
{
var feed = await new SyndicationClient().RetrieveFeedAsync(feedViewModel.Source);
//if (cancellationToken.HasValue && cancellationToken.Value.IsCancellationRequested) return false;
// If it is a new feed without in the database, we need to get the default basic info
bool isHaveNewArticles = false;
if (feedViewModel.Id == null)
{
// 第一次添加新的feed
feedViewModel.Name = string.IsNullOrEmpty(feedViewModel.Name) ? feed.Title.Text : feedViewModel.Name;
feedViewModel.Description = feed.Subtitle?.Text ?? feed.Title.Text;
feedViewModel.IconSrc = string.Empty;
feedViewModel.LastBuildedTime = feed.LastUpdatedTime.ToString();
feedViewModel.Id = await SQLiteService.InsertOrReplaceFeedAsync(feedViewModel.AbstractInfo());
var homePageLinkString = (feed.IconUri == null) ? feed.Links.Select(l => l.Uri).FirstOrDefault().ToString() : feed.IconUri.ToString();
await feedViewModel.TryUpdateIconSource(homePageLinkString);
// 现在UI上添加，缩短响应时间
MainPage.Current.ViewModel.Feeds.Add(feedViewModel);
isHaveNewArticles = true;
}
if (isHaveNewArticles || DateTimeOffset.Parse(feedViewModel.LastBuildedTime) < feed.LastUpdatedTime)
{
feedViewModel.LastBuildedTime = feed.LastUpdatedTime.ToString();
isHaveNewArticles = true;
}
if (isHaveNewArticles || feedViewModel.Articles.Count() == 0)
{
var articleInfoList = new List <ArticleInfo>();
// Get Article from the newly getted feed And sync
foreach (var item in feed.Items)
{
var newArticle = new ArticleModel(new ArticleInfo()
{
FeedId = (int)feedViewModel.Id,
Title = item.Title.Text,
PubDate = item.PublishedDate.ToString(),
// 借鉴了官方的获取本篇文章source的方法
Source = (item.ItemUri ?? item.Links.Select(l => l.Uri).FirstOrDefault()).ToString(),
Description = item.Summary == null ? "The article doesn't have description!" : item.Summary.Text,
Unread = true,
Isstarred = false
});
newArticle.Id = await SQLiteService.InsertOrReplaceArticleAsync(newArticle.AbstractInfo());
// 初始化那些不存在数据库里面的用于绑定的属性
newArticle.InitialOnlyBindingProperty(feedViewModel);
feedViewModel.Articles.Insert(0, newArticle);
}
}
else
{
Debug.Write("The feed is already the newest.");
}
feedViewModel.IsInError = false;
feedViewModel.ErrorMessage = null;
return(true);
}
catch (Exception)
{
if (!cancellationToken.HasValue || !cancellationToken.Value.IsCancellationRequested)
{
feedViewModel.IsInError = true;
feedViewModel.ErrorMessage = feedViewModel.Articles.Count == originalArticleNum ? BAD_URL_MESSAGE : NO_REFRESH_MESSAGE;
}
return(false);
}
}