Atlas快速入门之实战Atlas

发布时间：2006-09-21 10:53:55　来源：天极开发网友评论 0 条

　　首先，由于要处理XML，读取网站上的资源，所以要引入如下几个命名空间

Imports System.Net
Imports System.IO
Imports System.Xml

　　当用户点选某个分类主题的按钮时，将会自动下载该网站中符合主题的RSS XML文件，下载完后再进行解析，再显示到页面中去。代码如下：

Public Function SendRequest( _
ByVal URI As String, _
ByVal requestType As String) As HttpWebRequest
Dim req As HttpWebRequest = Nothing
Try
//发起HTTP请求
req = HttpWebRequest.Create(URI)
req.Method = requestType
Catch ex As Exception
Throw New Exception("Error")
End Try
Return req
End Function

Public Function GetResponse( _
ByVal req As HttpWebRequest) As String
Dim body As String = String.Empty
Try
//从服务器中获得响应输出流
Dim resp As HttpWebResponse = req.GetResponse()
Dim stream As Stream = resp.GetResponseStream()

//使用streamreader去处理得到的服务器响应
Dim reader As StreamReader = _
New StreamReader(stream, Encoding.UTF8)
body = reader.ReadToEnd()
stream.Close()
Catch ex As Exception
Throw New Exception("Error")
End Try
Return body
End Function

　　上面的两个方法，分别向网站服务器发出获取指定URL的信息的请求，并用IO流中的streamreader的方式获得服务器返回的输出信息。而下面的LoadRSS()方法，传入的参数是指定的URL地址，然后分别调用上面的两个方法，在最后获得服务器返回的输出流后，再通过解析XML的方式，选择合适的结点内容进行返回。代码如下：

Public Function LoadRSS( _
ByVal URI As String) As String
Dim req As HttpWebRequest
Dim xmlDoc As XmlDocument = Nothing
Try
XmlDataSource1.DataFile = URI

//下载RSS XML文件
req = SendRequest(URI, "GET")
Dim xmlData As String = GetResponse(req)
xmlDoc = New XmlDocument()
xmlDoc.LoadXml(xmlData)

//选择合适的结点
Dim titleNode As XmlNode = _
xmlDoc.DocumentElement.SelectSingleNode("channel/title")

Return titleNode.InnerText
Catch ex As Exception
　Return String.Empty
End Try
End Function

　　接着，我们还有为10多个按钮编写响应的事件，当点选了某个分类主题的按钮后，则向服务器请求指定的分类主题的RSS XML，代码如下：

Public Sub Button_Click( _
ByVal sender As Object, ByVal e As System.EventArgs) _
Handles Button1.Click, Button2.Click, Button3.Click, _
Button4.Click, Button5.Click, Button6.Click, _
Button7.Click, Button8.Click, Button9.Click, _
Button10.Click, Button11.Click

Dim URL As String = String.Empty
Select Case CType(sender, Button).Text
Case "Database" : URL = _
"http://services.devx.com/outgoing/databasefeed.xml"
Case ".NET" : URL = _
"http://services.devx.com/outgoing/dotnet.xml"
Case "C++" : URL = _
"http://services.devx.com/outgoing/cplusfeed.xml"
Case "Recent Tips" : URL = _
"http://services.devx.com/outgoing/recentTipsFeed.xml"
Case "Web Dev" : URL = _
"http://services.devx.com/outgoing/webdevfeed.xml"
Case "Latest" : URL = _
"http://services.devx.com/outgoing/devxfeed.xml"
Case "Enterprise" : URL = _
"http://services.devx.com/outgoing/enterprisefeed.xml"
Case "Wireless / Mobile" : URL = _
"http://services.devx.com/outgoing/wirelessfeed.xml"
Case "XML" : URL = _
"http://services.devx.com/outgoing/xmlfeed.xml"
Case "Java" : URL = _
"http://services.devx.com/outgoing/javafeed.xml"
Case "Open Source" : URL = _
"http://services.devx.com/outgoing/openSourceFeed.xml"
End Select
Label1.Text = LoadRSS(URL)
End Sub

　　最后，在LOAD事件中,默认读取最新信息的RSS XML

Protected Sub Page_Load( _
ByVal sender As Object, _
ByVal e As System.EventArgs) Handles Me.Load
Label1.Text = _
LoadRSS("http://services.devx.com/outgoing/devxfeed.xml")
End Sub

　　运行后效果如下图所示,点选左边每个分类主题的按钮，都会自动去该网站下载最新的RSS XML 并且进行解析，最后展示到页面中去，而这一切都由于用了Atlas而是无刷新的。