如何打造RSS阅读器

如何打造RSS阅读器

                             电子科技大学软件学院03级02班 周银辉

关键点：下载RSS订阅所对应的XML文件，解析该XML文件

该类XML文件其形如：

<? xml version="1.0" encoding="utf-8" standalone="yes"  ?>  
  < rss  version ="2.0"  xmlns:dc ="http://purl.org/dc/elements/1.1/"  xmlns:trackback ="http://madskills.com/public/xml/rss/module/trackback/"  xmlns:wfw ="http://wellformedweb.org/CommentAPI/"  xmlns:slash ="http://purl.org/rss/1.0/modules/slash/" >
  < channel >
   < title > 博客园-this.Study(DateTime.Now) </ title >  
   < link > http://www.cnblogs.com/zhouyinhui/ </ link >  
   < description > 专业因为专注 </ description >  
   < language > zh-cn </ language >  
   < lastBuildDate > Mon, 16 Oct 2006 05:33:31 GMT </ lastBuildDate >  
   < pubDate > Mon, 16 Oct 2006 05:33:31 GMT </ pubDate >  
   < ttl > 60 </ ttl >  
  < item >
   < title > 真正的代码宝库：Google Code Search </ title >  
   < link > http://www.cnblogs.com/zhouyinhui/archive/2006/10/13/528421.html </ link >  
   < dc:creator > 周银辉 </ dc:creator >  
   < author > 周银辉 </ author >  
   < pubDate > Fri, 13 Oct 2006 09:12:00 GMT </ pubDate >  
   < guid > http://www.cnblogs.com/zhouyinhui/archive/2006/10/13/528421.html </ guid >  
   < wfw:comment > http://www.cnblogs.com/zhouyinhui/comments/528421.html </ wfw:comment >  
   < comments > http://www.cnblogs.com/zhouyinhui/archive/2006/10/13/528421.html#Feedback </ comments >  
   < slash:comments > 2 </ slash:comments >  
   < wfw:commentRss > http://www.cnblogs.com/zhouyinhui/comments/commentRss/528421.html </ wfw:commentRss >  
   < trackback:ping > http://www.cnblogs.com/zhouyinhui/services/trackbacks/528421.html </ trackback:ping >  
  < description >
   <![CDATA[  Google推出代码搜索&nbsp;，可以搜索到无数的开源代码，有让人欣喜若狂的感觉啊.<BR><BR>不用多说，快去看看 <A href="http://www.google.com/codesearch">http://www.google.com/codesearch</A><img src ="http://www.cnblogs.com/zhouyinhui/aggbug/528421.html" width = "1" height = "1" /><br><br><div align=right><a style="text-decoration:none;" href="http://zhouyinhui.cnblogs.com/" target="_blank">周银辉</a> 2006-10-13 17:12 <a href="/zhouyinhui/archive/2006/10/13/528421.html#Feedback" target="_blank" style="text-decoration:none;">发表评论</a></div>
   ]]>  
   </ description >
  </ item >
  </ channel >
  </ rss >

如何下载

可以简单地利用 System.Net.WebClient 类，其对象有一个OpenRead(string url)方法，该方法可以打开一个Stream，可以使用该Stream来创建一个XmlDocument

 WebClient client  =   new  WebClient();
 XmlDocument doc  =   null ;

             try
             {
                using (Stream stream = client.OpenRead(url))
                {
                    doc = new XmlDocument();
                    doc.Load(stream);
                }
            }
             catch
             {
                throw;
            }

             if  (doc  !=   null )
             {
               // do something else
            }

如何解析下载的XML文件：

注意到这样一个层次关系：一个RSS包含n个RssFeed，一个RssFeed包含n个RssChannel，RssChannel一个包含n个Item。这里的Item即一个项，它通常是一篇文章，包含标题、Url地址、简短描述等等.

RssItem:

using System;
using System.Collections.Generic;
using System.Text;
using System.Xml;

namespace DemoForRss.RSS
{

    public class RssItem
    {

        private string title;
        private string link;
        private string description;

  

        /**//// <summary>
        /// 获取该项的标题
        /// </summary>
        public string Title
        {
            get
            {
                return this.title;
            }
            set
            {
                this.title = value;
            }
        }

        /**//// <summary>
        /// 获取该项的Url地址
        /// </summary>
        public string Link
        {
            get
            {
                return this.link;
            }
            
        }

        /**//// <summary>
        /// 获取该项的描述信息
        /// </summary>
        public string Description
        {
            get
            {
                return this.description;
            }
            
        }

        public RssItem()
        {
        }

        /**//// <summary>
        /// 从“item”节点构造一个项
        /// </summary>
        /// <param name="itemNode"></param>
        public RssItem(XmlNode itemNode)
        {
            if (itemNode != null)
            {
                XmlNode nodeTitle = itemNode.SelectSingleNode("title");
                if (nodeTitle != null)
                {
                    this.title = nodeTitle.InnerText;
                }

                XmlNode nodeLink = itemNode.SelectSingleNode("link");
                if (nodeLink != null)
                {
                    this.link = nodeLink.InnerText;
                }

                XmlNode nodeDescription = itemNode.SelectSingleNode("description");
                if (nodeDescription != null)
                {
                    this.description = nodeDescription.InnerText;
                }
            }
        }
    }
}

RssChannel

RssChannel
 1using System;
 2using System.Collections.Generic;
 3using System.Text;
 4using System.Xml;
 5
 6namespace DemoForRss.RSS
 7{
 8    /**//// <summary>
 9    /// Rss频道，包含0个或多个RssItem
10    /// </summary>
11    public class RssChannel
12    {
13        private string title;
14        private string link;
15        private List<RssItem> itemList = new List<RssItem>();
16
17        /**//// <summary>
18        /// 获取该项的标题
19        /// </summary>
20        public string Title
21        {
22            get
23            {
24                return this.title;
25            }
26           
27        }
28
29        /**//// <summary>
30        /// 获取该项的Url地址
31        /// </summary>
32        public string Link
33        {
34            get
35            {
36                return this.link;
37            }
38           
39        }
40
41        /**//// <summary>
42        /// 获取其RssItem列表的只读副本
43        /// </summary>
44        public List<RssItem> ItemList
45        {
46            get
47            {
48                return this.itemList;
49            }
50            
51        }
52
53        public RssChannel()
54        {
55        }
56
57        /**//// <summary>
58        /// 由“channel”节点构造RssChannel对象
59        /// </summary>
60        /// <param name="nodeChannel"></param>
61        public RssChannel(XmlNode nodeChannel)
62        {
63            if (nodeChannel != null)
64            {
65                XmlNode nodeTitle = nodeChannel.SelectSingleNode("title");
66                if (nodeTitle != null)
67                {
68                    this.title = nodeTitle.InnerText;
69                }
70
71                XmlNode nodeLink = nodeChannel.SelectSingleNode("link");
72                if (nodeLink != null)
73                {
74                    this.link = nodeLink.InnerText;
75                }
76
77                foreach (XmlNode nodeItem in nodeChannel.SelectNodes("item"))
78                {
79                    this.itemList.Add(new RssItem(nodeItem));
80                }
81            }
82        }
83    }
84}
85

 

RssFeed

RssFeed
using System;
using System.Collections.Generic;
using System.Text;
using System.Net;
using System.Xml;
using System.IO;


namespace DemoForRss.RSS
{
    /**//// <summary>
    /// RssFeed，它由0个或多个RssChannel组成
    /// </summary>
    [Serializable()]
    public class RssFeed
    {
        private List<RssChannel> channelList = new List<RssChannel>();
        private string url = "";
        private string path = "";

        public RssFeed()
        {
        }

        /**//// <summary>
        /// 获取该Feed对应的Xml文件的本机地址,它是网络上的Xml文件的副本
        /// </summary>
        public string Path
        {
            get
            {
                return this.path;
            }
            
        }

        /**//// <summary>
        /// 获取该Feed对应的Xml文件的网络地址
        /// </summary>
        public string Url
        {
            get
            {
                return this.url;
            }
            
        }

        /**//// <summary>
        /// 获取频道列表（一般只有一个频道）
        /// </summary>
        public List<RssChannel> ChannelList
        {
            get
            {
                return channelList;
            }
        }

        /**//// <summary>
        /// 获取频道列表中的第一个频道(主频道)
        /// </summary>
        public RssChannel FirstChannel
        {
            get
            {
                if (channelList.Count > 0)
                {
                    return channelList[0];
                }

                return null;
            }
        }

        /**//// <summary>
        /// 从指定网址加载RssFeed信息
        /// </summary>
        /// <param name="url"></param>
        /// <param name="saveTo">将下载到的文件保存到这里，如果不保存请填写null</param>
        public void LoadFormUrl(string url, string saveTo)
        {
            WebClient client = new WebClient();
            XmlDocument doc = null;

            try
            {
                using (Stream stream = client.OpenRead(url))
                {
                    doc = new XmlDocument();
                    doc.Load(stream);
                }
            }
            catch
            {
                throw;
            }

            if (doc != null)
            {
                foreach (XmlNode nodeRss in doc.SelectNodes("rss"))
                {
                    if (nodeRss != null)
                    {
                        foreach (XmlNode nodeChannel in nodeRss.SelectNodes("channel"))
                        {
                            this.channelList.Add(new RssChannel(nodeChannel));
                        }
                    }
                }

                if (!string.IsNullOrEmpty(saveTo))
                {
                    try
                    {
                        doc.Save(saveTo);
                    }
                    catch
                    {
                    }
                }
            }

            this.url = url;


        }

        /**//// <summary>
        /// 从指定文件加载RssFeed信息
        /// </summary>
        /// <param name="path"></param>
        public void LoadFormPath(string path)
        {
            try
            {
                XmlDocument doc = new XmlDocument();
                doc.Load(path);

                foreach (XmlNode nodeRss in doc.SelectNodes("rss"))
                {
                    if (nodeRss != null)
                    {
                        foreach (XmlNode nodeChannel in nodeRss.SelectNodes("channel"))
                        {
                            this.channelList.Add(new RssChannel(nodeChannel));
                        }
                    }
                }

                this.path = path;
            }
            catch
            {
                throw;
            }

        }


    }
}

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下载Demo： http://www.cnblogs.com/Files/zhouyinhui/DemoForRss.rar
文章来源于 http://www.cnblogs.com/zhouyinhui 版权归原作者所有