Our second Twitter giveaway contest has finished. We’re glad to announce the nicks of the 4 winners, one of each will get a free redeem code for the full Little Racers game:
Congratulations to all of them! Each one should have received their code on a direct message via Twitter. The codes will have a validity of three months, if they haven’t been used by then it we’ll consider them as available for future promotions.
Little Racers has just reached 2,500 sales on Xbox Live Indie Games! To celebrate it, we’re giving away 4 free codes of the game.
If you’re interested in receiving one of these free codes, all you have to do is retweet our message on Twitter. On September 12th, we’ll pick the winners at random. Codes will be sent via direct message on Twitter.
Meanwhile, you can try the game on your Xbox 360 and have some fun playing the demo version!
During the first stages of Little Racers development, I found the need of parsing XML data during the game load. The XNA Content Pipeline system includes XML Parsing, but it uses it in a very particular way. I won’t go much further in the way XNA parses XML because, to be sincere, I’ve not tried it enough to test wether it’s good or not.
My first impression was that it was too strict (probably due to optimization and type safe issues), moreover during parse I would need access to some data structures that only were available at runtime, so I preferred to store plain XML and parse it during game load.
This can be done by extending the content pipeline and adding a new type. To do this we’ll need to add two new projects to our solution.
The first project we’ll create is the one which has the class that stores our xml plain text. I’ve called it XmlSource.It will have two classes in total.
This class is a very simple one. It simply has a string with the xml plain text:
[sourcecode language=’csharp’]
public class XmlSource
{
public XmlSource(string xmlCode)
{
this.xmlCode = xmlCode;
}
private string xmlCode;
public string XmlCode { get { return xmlCode; } }
}
[/sourcecode]
This class extends ContentTypeReader and simply creates an XmlSource instance from its binary representation. In our case, the binary representation wil be a simple string, so the read is straightforward.
[sourcecode language=’csharp’]
public class XmlSourceReader : ContentTypeReader
{
///
protected override XmlSource Read(ContentReader input, XmlSource existingInstance)
{
string xmlData = input.ReadString();
return new XmlSource(xmlData);
}
}
[/sourcecode]
With this, our first project is finished. This project is platform-independant (The Xbox needs to read the binary data) and will have to be referenced from every project that uses the XmlSource class, including the second project we’re making:
The second project(I called it XmlDocumentImporter) is a project of type “Content Pipeline Extension Library”. This project is referenced from the Content projects, and converts the source text file to binary data that will be saved in the .xnb files.
This project has 2 files:
This file converts the XML source file into an XmlSource instance, that will be further converted into binary data
[sourcecode language=’csharp’]
[ContentImporter(“.xml”, DisplayName = “Xml Source Importer”)]
class XmlSourceImporter : ContentImporter
{
public override XmlSource Import(string filename, ContentImporterContext context)
{
string sourceCode = System.IO.File.ReadAllText(filename);
return new XmlSource(sourceCode);
}
}
[/sourcecode]
This file converts an XmlSource into binary data, as opposed to XmlSourceReader
[sourcecode language=’csharp’]
[ContentTypeWriter]
class XmlSourceWriter : ContentTypeWriter
{
protected override void Write(ContentWriter output, XmlSource value)
{
/*StringWriter sw=new StringWriter();
value.Save(sw);
string content = sw.ToString();*/
output.Write(value.XmlCode);
}
public override string GetRuntimeType(TargetPlatform targetPlatform)
{
return typeof(XmlDocument).AssemblyQualifiedName;
}
public override string GetRuntimeReader(TargetPlatform targetPlatform)
{
return typeof(XmlDocumentReader).AssemblyQualifiedName;
}
}
[/sourcecode]
Once both projects set up (remember to add reference to XmlSourceImporter from the Content project), we can add .xml files to the content project. Under “Content importer”, we’ll need to select “Xml Source importer”, instead of the default XNA one.
Once done this, the program sould compile ok. Loading XML from the program now is very easy:
[sourcecode language=’csharp’]
XmlSource xs = Content.Load
XmlDocument xd = new XmlDocument();
xd.LoadXml(xs.XmlCode);
[/sourcecode]
I know this can be a little confusing, i’ll upload some binaries if someone asks for them.
PS: Here they are: Plain Xml Content Importer