Which API should I use? – Using the .NET Compact Framework.

Blogger : MSDN Blogs
All posts : All posts by MSDN Blogs
Category : SAP BW and BIW
Blogged date : 2008 Oct 09

A couple of days ago I published an article which talked about a session I’m presenting at ESC East on choosing an API for your embedded device – The plan is to show building a FrameIt enabled Picture Frame (RSS Feed with image enclosures).

The application has three parts.

Pull down the FrameIt XML feed
Parse the XML feed – pull out the enclosures (URL to an image)
Pull down the images and display them on the screen

I’ve written a simple application that clearly shows each of the three phases – Here’s the application running on the desktop.

Here’s the same code (no source code changes) running on the Windows CE 6.0 Emulator

And now the code…

1. Get the RSS Feed from FrameIt http://demofeed.frameit.com

   1:              WebRequest request = WebRequest.Create("http://demofeed.frameit.com");

   2:              WebResponse response = request.GetResponse();

   3:              StreamReader sr = new StreamReader(response.GetResponseStream());

   4:              string str=sr.ReadToEnd();

   5:              textBox1.Text = str;

   6:              response.Close();

   7:              StreamWriter sw = new StreamWriter(strXMLFile);

   8:              sw.Write(str);

   9:              sw.Close();

2. Parse the XML – In this case I’m building an ArrayList of the Image URLs.

   1:          private void ParseXML(string strFilename)

   2:          {

   3:              string strURL = null;

   4:              iArrayListPointer = 0;

5:

   6:              Console.WriteLine("Parsing - " + strFilename);

   7:              if (File.Exists(strFilename))

   8:              {

   9:                  XmlTextReader reader = new XmlTextReader(strFilename);

  10:                  while (reader.Read())

  11:                  {

  12:                      switch (reader.NodeType)

  13:                      {

  14:                          case XmlNodeType.Element: // The node is an element.

  15:                              if (reader.Name == "enclosure")

  16:                              {

  17:                                  Console.WriteLine("enclosure...");

  18:                                  if (reader.AttributeCount > 0)

  19:                                  {

  20:                                      strURL = reader.GetAttribute("url");

  21:                                      if (null != strURL)

  22:                                      {

  23:                                          Console.WriteLine("strURL == " + strURL);

  24:                                          ar.Add(strURL);

  25:                                      }

  26:                                  }

  27:                              }

  28:                              Console.Write("<" + reader.Name);

  29:                              Console.WriteLine(">");

  30:                              break;

  31:                      }

  32:                  }

  33:                  Console.WriteLine("---------------------------------------");

  34:              }

  35:          }

3. Now get the image (store in the local file system, so we don’t need to get it every time we display the image), and display the image in a PictureBox.

   1:          private void GetAndDisplayImage(string strURL,int iIndex)

   2:          {

3:

   4:              string strFile= @"c:\demo\foo"+iIndex.ToString()+".jpg";

   5:              if (!File.Exists(strFile))

   6:              {

   7:                  WebRequest request = WebRequest.Create(strURL);

   8:                  WebResponse response = request.GetResponse();

   9:                  long iFileSize = response.ContentLength;

  10:                  BinaryReader br = new BinaryReader(response.GetResponseStream());

  11:                  FileStream fs = new FileStream(strFile, System.IO.FileMode.CreateNew);

  12:                  BinaryWriter bw = new BinaryWriter(fs);

  13:                  byte[] bArray = new byte[iFileSize];

  14:                  int iRead = 0;

  15:                  do

  16:                  {

  17:                      iRead = br.Read(bArray, 0, Convert.ToInt32(iFileSize));

  18:                      bw.Write(bArray, 0, iRead);

  19:                  }

  20:                  while (iRead > 0);

  21:                  bw.Flush();

  22:                  bw.Close();

  23:                  fs.Close();

  24:                  br.Close();

  25:                  response.Close();

  26:              }

  27:              pictureBox1.Image = new Bitmap(strFile);

  28:          }

Next step is to reproduce the same three steps in Native/Win32 code (rolls up sleeves), makes sure that Coffee cup is full… Look out for the next post coming soon (at least before ESC East).

- Mike

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