在WP7阅读RSS
原文地址：http://www.codeproject.com/Articles/153472/Reading-RSS-items-on-Windows-Phone-7
下面是我写的一个帮助我在WP7中阅读RSS工具类。我将介绍如何去写并且如何使用它。
文章结束的地方可以找到一个包含所有代码的简单示例。
如何去读RSS
添加一个Helper程序集
第一步我们将添加一个程序集的引用 System.ServiceModel.Syndication.dll (包含解析RSS的类)
这个程序集属于Silverlight3 sdk,不属于Windows Phone sdk,但是在这使用它是没问题的。
你在以下路径中可以找到它：%ProgramFiles%\Microsoft SDKs\Silverlight\v3.0\Libraries\Client\System.ServiceModel.Syndication.dll
你可能会遇到以下警告,忽略继续…
定义 RssItem类
我们需定义一个模型类来装载rss项数据
我们的RssItem类将包含以下几个属性：Title, Summary, PublishedDate and Url, PlainSummary
/// <summary>
/// Model for RSS item
/// </summary>
public class RssItem
{
/// <summary>
/// Initializes a new instance of the <see cref="RssItem"/>class.
/// </summary>
/// <param name="title">The title.</param>
/// <param name="summary">The summary.</param>
/// <param name="publishedDate">The published date.</param>
/// <param name="url">The URL.</param>
public RssItem(string title, string summary, string publishedDate, string url)
{
Title = title;
Summary = summary;
PublishedDate = publishedDate;
Url = url;
//Get plain text from html
PlainSummary = HttpUtility.HtmlDecode(Regex.Replace(summary, "<[^>]+?>",""));
}
/// <summary>
/// Gets or sets the title.
/// </summary>
/// <value>The title.</value>
public string Title { get; set; }
/// <summary>
/// Gets or sets the summary.
/// </summary>
/// <value>The summary.</value>
public string Summary { get; set; }
/// <summary>
/// Gets or sets the published date.
/// </summary>
/// <value>The published date.</value>
public string PublishedDate { get; set; }
/// <summary>
/// Gets or sets the URL.
/// </summary>
/// <value>The URL.</value>
public string Url { get; set; }
/// <summary>
/// Gets or sets the plain summary.
/// </summary>
/// <value>The plain summary.</value>
public string PlainSummary { get; set; }
}
订阅服务
RSS服务通过一个参数获得RSS 的URL地址。另外，我们需要定义一些委托参数去实现异步调用：
- Action<IEnumerable<RssItem>> onGetRssItemsCompleted, 在 RSS items准备进行处理时调用。
- Action<Exception> onError, 在获取RSS items时发生异常调用
- Action onFinally,不管是否有异常,它将作为作为try-catch-finally块进行调用
-
下面是方法签名：
public static void GetRssItems(string rssFeed,
Action<IEnumerable<RssItem>> onGetRssItemsCompleted = null,
Action<Exception> onError = null,
Action onFinally = null)
使用 WebClient 获取 feed xml.
WebClient webClient = new WebClient();
// register on download complete event
webClient.OpenReadCompleted += delegate(object sender, OpenReadCompletedEventArgs e)
{
...
};
webClient.OpenReadAsync(new Uri(rssFeed));
在我们的 helper 程序集中 , 实际上是用 SyndicationFeed 类来解析 RSS.
// convert rss result to model
List<RssItem> rssItems = new List<RssItem>();
Stream stream = e.Result;
XmlReader response = XmlReader.Create(stream);
SyndicationFeed feeds = SyndicationFeed.Load(response);
foreach (SyndicationItem f in feeds.Items)
{
RssItem rssItem = new RssItem(f.Title.Text, f.Summary.Text,f.PublishDate.ToString(), f.Links[0].Uri.AbsoluteUri);
rssItems.Add(rssItem);}
其余的代码是处理不同的委托： onCompleted, onError and onFinally
/// <summary>
/// Gets the RSS items.
/// </summary>
/// <param name="rssFeed">The RSS feed.</param>
/// <param name="onGetRssItemsCompleted">The on get RSS items completed.</param>
/// <param name="onError">The on error.</param>
public static void GetRssItems(string rssFeed, Action<IEnumerable<RssItem>> onGetRssItemsCompleted = null, Action<Exception> onError = null, Action onFinally = null)
{
WebClient webClient = new WebClient();
// register on download complete event
webClient.OpenReadCompleted += delegate(object sender, OpenReadCompletedEventArgs e)
{
try
{
// report error
if(e.Error != null)
{
if (onError != null)
{
onError(e.Error);
}
return;
}
// convert rss result to model
List<RssItem> rssItems = new List<RssItem>();
Stream stream =e.Result;
XmlReader response =XmlReader.Create(stream);
SyndicationFeed feeds =SyndicationFeed.Load(response);
foreach(SyndicationItem f in feeds.Items)
{
RssItem rssItem = new RssItem(f.Title.Text, f.Summary.Text, f.PublishDate.ToString(), f.Links[0].Uri.AbsoluteUri);
rssItems.Add(rssItem);
}
// notify completed callback
if(onGetRssItemsCompleted != null)
{
onGetRssItemsCompleted(rssItems);
}
}
finally
{
// notify finally callback
if(onFinally != null)
{
onFinally();
}
}
};
webClient.OpenReadAsync(new Uri(rssFeed));
}
使用RSS 服务
使用这个服务是非常简单的，只要提供URL作为第一个参数,并且定义一个委托来处理“completed”通知.
private void Button_Click(object sender, RoutedEventArgs e)
{
RssService.GetRssItems(
WindowsPhoneBlogPosts,
(items) => {listbox.ItemsSource = items; },
(exception) => {MessageBox.Show(exception.Message); },
null
);
}
下面是一个简单的例子,代码下载地址 here.
