在上篇文章介绍了Http Server，通过PC上的IE浏览器（相当于Http client）来访问开发板上的Http服务。这次我们在网络开发板上实现Http Client，获取雅虎网站的天气信息，并把这些信息在LCD上显示出来。
包含两部分的代码，一是通过Http协议获取数据，二是对获取的网页，进行XML解析，以期获取天气信息。
主程序很简单，就是web服务请求和画面显示。
public static void Main()
{
try
{
weather = new yahooWeatherRequest();
weather.webRequest();
}
catch
{
Debug.Print("Error!");
}
WindowsDrawing win = new WindowsDrawing();
win.Width = SystemMetrics.ScreenWidth;
win.Height = SystemMetrics.ScreenHeight;
new Program().Run(win);
}创建Http请求，并获取数据，相关代码如下：
private byte[] getHttpData(string url)
{
HttpWebRequest request = HttpWebRequest.Create(url) as HttpWebRequest;
request.HttpsAuthentCerts = null;
request.KeepAlive = true;
WebResponse resp = null;
Stream respStream = null;
byte[] bytData = null;
try
{
resp = request.GetResponse();
}
catch (Exception e)
{
Debug.Print("Exception in HttpWebRequest.GetResponse(): " + e.Message.ToString());
return null;
}
if (resp != null)
{
respStream = resp.GetResponseStream();
int bytesRead = 0;
int totalBytes = 0;
respStream.ReadTimeout = 5000;
Debug.Print("resp length= " + resp.ContentLength.ToString());
if (resp.ContentLength!=-1)
{
bytData = new byte[resp.ContentLength];
while (totalBytes < bytData.Length)
{
bytesRead = respStream.Read(bytData, totalBytes, bytData.Length - totalBytes);
if (bytesRead == 0)
{
Debug.Print("Error: Received " + totalBytes.ToString() + " Out of " + bytData.Length.ToString());
bytData = null;
break;
}
totalBytes += bytesRead;
Debug.Print("Bytes Read Now 0: " + bytesRead + " Total: " + totalBytes);
}
return bytData;
}
}
if (respStream != null) respStream.Close();
if (resp != null) resp.Close();
request = null;
return bytData;
}数据获取后，进行必要的XML解析，以提取天气数据。
private void parseRssPage(byte[] rssPage)
{
MemoryStream mStream = new MemoryStream(rssPage);
XmlReader xReader = XmlReader.Create(mStream);
forcastArray = new ArrayList();
while (xReader.Read())
{
if (xReader.NodeType == XmlNodeType.Element)
{
switch (xReader.Name)
{
case "title":
xReader.Read();
break;
case "pubDate":
xReader.Read();
break;
case "yweather:location":
myCity = new cityInfo(xReader.GetAttribute("city"), xReader.GetAttribute("region"), xReader.GetAttribute("country"));
break;
case "yweather:condition":
today = new todayCondition(xReader.GetAttribute("text"), xReader.GetAttribute("temp"), xReader.GetAttribute("date"));
break;
case "yweather:forecast":
forcastArray.Add(new forcastCondition(xReader.GetAttribute("day"), xReader.GetAttribute("date"), xReader.GetAttribute("low"),
xReader.GetAttribute("high"), xReader.GetAttribute("text")));
break;
}
}
else if (xReader.NodeType == XmlNodeType.CDATA)
parseCDATA(xReader.Value);
}
}数据解析完毕后，就进行屏幕显示了。
public override void OnRender(DrawingContext dc)
{
dc.DrawRectangle(new SolidColorBrush(Colors.White), new Pen(Colors.White), 0, 0, Width, Height);
dc.DrawLine(new Pen(Colors.Gray), 10, 46, 310, 46); dc.DrawImage(Resources.GetBitmap(Resources.BitmapResources.yahoo_news_wea), 10, 10);
if (Program.weather != null)
{
int Y = 60;
if (weather.MyCity != null) dc.DrawText(weather.MyCity.ToString(), Resources.GetFont(Resources.FontResources.small), Colors.Black, 10, Y);
if (weather.Today != null)
{
dc.DrawText(weather.Today.date, Resources.GetFont(Resources.FontResources.small), Colors.Black, 10, Y + 20);
dc.DrawText(weather.Today.weahterDesc + " temperature: " + weather.Today.curTemp + "c", Resources.GetFont(Resources.FontResources.small), Colors.Black, 10, Y + 40);
}
dc.DrawText("Forcast -- this week:", Resources.GetFont(Resources.FontResources.small), Colors.Black, 10, Y + 80);
Y += 80;
if (weather.ForcastArray != null)
{
foreach (yahooWeatherRequest.forcastCondition forcast in weather.ForcastArray)
{
string info = forcast.date + " , " + forcast.day + " , " + forcast.weahterDesc + " , " + forcast.lowTemp + "c ~ " + forcast.highTemp + "c ";
Y += 20;
dc.DrawText(info, Resources.GetFont(Resources.FontResources.small), Colors.Black, 10, Y);
}
}
}保证开发板正确的接入互联网，注意设置好DNS服务器（这个事例也可以不用设置，不过如果测试官方的HttpClient事例，是一定要设置的，因为目前MF的LWIP协议栈不支持默认的DNS），运行程序，则在超级终端中，我们可以看到我们从互联网上请求的数据（如下图）：
开发板运行后的画面如下：
开发板最新的固件版本：V0.9.06 下载地址：http://www.sky-walker.com.cn/MFRelease/firmware/mfv41_firmware_hy_redbull.rar
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源码/文档：http://www.sky-walker.com.cn/MFRelease/Sample/YFHttpClient.rar
MF快速入门：http://blog.csdn.net/yefanqiu/article/details/5340560
MF论坛：http://space.cnblogs.com/group/MFSoft/
