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

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/

MF开发板：http://item.taobao.com/item.htm?id=7117999726

网络开发板：http://item.taobao.com/item.htm?id=10919470266

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