/// <summary>
/// Try to Get The Favicon From the homepage Server
/// Use Google tool, So please ensure your computer unblocked Google
/// </summary>
///
public static async Task TryUpdateIconSource(this FeedViewModel feedViewModel, string HomePageUrl)
{
if (feedViewModel.IconSrc.ToString() != string.Empty)
{
return;
}
if (HomePageUrl == string.Empty)
{
return;
}
//一般这个不会发生
var feedId = feedViewModel.Id ?? -1;
int numberOfAttempts = 2;
bool success = false;
// 尝试下载2次
do
{
success = await WebIconDownloadTool.DownLoadIconFrom_IconUri(HomePageUrl, feedId.ToString());
} while (!success && numberOfAttempts-- > 0);
// 如果成功,更新IconSrc, iconsrc为下载的图片文件的文件名，否则IconSrc还会是默认的那个图标路径
if (success)
{
feedViewModel.IconSrc = feedId.ToString() + ".png";
await SQLiteService.UpdateFeedInfoAsync(feedViewModel.AbstractInfo());
}
}
public static void InitialOnlyBindingProperty(this ArticleModel a, FeedViewModel feedViewModel)
{
a.FeedName = feedViewModel.Name;
a.FeedIconSource = feedViewModel.ShortcutIcon;
a.Summary = a.Description.RegexRemove("\\&.{0,4}\\;").RegexRemove("<.*?>");
a.FeedIconSourceAsString = feedViewModel.IconSrc.ToString();
}
/// <summary>
/// Populates the Feeds list and initializes the CurrentFeed property.
/// </summary>
public async Task InitializeFeedsAsync()
{
// FeedDataSource.GetStarredFeedAsync()这个异步方法已经弃用，为了同步starredFeed的内容
// 逻辑改成了在构建普通Feed的时候同时插入构建starredFeed，可以work
//StarredFeed = await FeedDataSource.GetStarredFeedAsync();
StarredFeed = new FeedViewModel();
var res = await FeedDataSource.GetFeedsAsync();
foreach (var feed in res)
{
Feeds.Add(feed);
}
CurrentFeed = Feeds.Count == 0 ? StarredFeed : Feeds[0];
if (StarredFeed.Articles.Count == 0)
{
StarredFeed.ErrorMessage = NO_ARTICLES_MESSAGE;
}
StarredFeed.Articles.CollectionChanged += async(s, e) =>
{
// This handles list saving for both newly-starred items and for
// reordering of the Favorites list (which causes a Remove followed by an Add).
// List saving for removals due to an unstarring are handled in FeedView.xaml.cs.
if (e.Action == NotifyCollectionChangedAction.Add)
{
await SaveArticlesAsync();
}
StarredFeed.ErrorMessage = StarredFeed.Articles.Count > 0 ? null : NO_ARTICLES_MESSAGE;
};
}
public static void UpdateArticlesFeedName(this FeedViewModel feedViewModel)
{
// 不知道如何改变它本来的内容
var li = feedViewModel.Articles.ToList();
var newFeedName = feedViewModel.Name;
feedViewModel.Articles.Clear();
foreach (var x in li)
{
x.FeedName = newFeedName;
feedViewModel.Articles.Add(x);
}
}
public static async Task ClearOutTimeArticlesAsync(this FeedViewModel feedViewModel)
{
var original = feedViewModel.Articles;
// 更新视图集合
var temp = feedViewModel.Articles.ToList();
temp.RemoveAll(x => x.UnRead == false && x.IsStarred == false);
foreach (var item in temp)
{
feedViewModel.Articles.Remove(item);
}
var ClearArticles = from x in original
where x.UnRead == false && x.IsStarred == false
select x.AbstractInfo();
await SQLiteService.RemoveArticlesAsync(ClearArticles);
}
/// <summary>
/// Try to get the old articles in the database
/// 这是一个可扩展的方法。
/// </summary>
private static async Task LoadArticlesFromDb(this FeedViewModel feedViewModel)
{
if (feedViewModel.Id != null)
{
feedViewModel.Articles.Clear();
// working here
feedViewModel.IsLoading = true;
(await SQLiteService.QueryAritclesByFeedIdAsync((int)feedViewModel.Id)).Select(item => new ArticleModel(item))
.ToList().ForEach(article =>
{
article.InitialOnlyBindingProperty(feedViewModel);
feedViewModel.Articles.Insert(0, article);
// 在这里在开始的时候添加Favourite的文章
if (article.IsStarred)
{
MainPage.Current.ViewModel.StarredFeed.Articles.Insert(0, article);
}
});
feedViewModel.IsLoading = false;
}
return;
}
// 添加扩展方法来方便MainViewModel来从上面控制refresh
/// <summary>
/// Attempts to update the feed with new data from the server.
/// 想要在原来的基础上加入新的文章
/// 这是一个可扩展的方法。
/// </summary>
//// Cancellation 还是不是太懂，先保留一下
public static async Task RefreshAsync(this FeedViewModel feedViewModel, CancellationToken?cancellationToken = null)
{
if (feedViewModel.Source.Host == "localhost" ||
(feedViewModel.Source.Scheme != "http" && feedViewModel.Source.Scheme != "https"))
{
return;
}
feedViewModel.IsLoading = true;
int numberOfAttempts = 5;
bool success = false;
// 在这里进行了一波阻塞
// 这个do-while循环的判断条件贼强，判断了是否成功，总共是第几次尝试，还有是否取消，一并给判断了，强
// 5 次都没有成功， 就跳出来
do
{
success = await TryGetFeedFromServerAsync(feedViewModel, cancellationToken);
}while (!success && numberOfAttempts-- > 0 &&
(!cancellationToken.HasValue || !cancellationToken.Value.IsCancellationRequested));
feedViewModel.IsLoading = false;
}
/// <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);
}
}
/// <summary>
/// Saves the favorites feed (the first feed of the feeds list) to local storage.
/// </summary>
public static async Task SaveArticlesAsync(this FeedViewModel feedviewmodel)
{
await SQLiteService.SaveArticlesInfoAsync(feedviewmodel.Articles.Select(article => article.AbstractInfo()));
}
public static async Task RemoveAFeedAsync(this FeedViewModel feedViewModel)
{
await SQLiteService.RemoveAFeedAsync(feedViewModel.AbstractInfo());
}
/// <summary>
/// Delete All the Related Articles in DataBases.
/// </summary>
public static async Task RemoveRelatedArticlesAsync(this FeedViewModel feedViewModel)
{
await SQLiteService.RemoveArticlesAsync(feedViewModel.Articles.Select(article => article.AbstractInfo()));
feedViewModel.Articles.Clear();
}
