James Darbyshire

12 May 2012

Resources in MonoTouch assembly

In my experience, I found that adding resources into a MonoTouch project can be slightly confusing - if you have not done it before.

I had a requirement to embed images into a project… easy you may say. Add a solution folder into the solution, add your images into the folder and give them a build action of ‘Content’. Duh… Why bother with a blog post? I hear the crowd mutter.

Well… It on the surface it is easy. The process is:

  1. Right click on the solution, and select “Add > Add Files”
  2. Select your image and click “open”
  3. Choose to “Copy the file to the directory”
  4. Set the Build Action to “Content” (In the properties panel)

Done… You can access the image by loading it using a directive which is relative to the root of the app. In this case it would be:

_Resources\Xamarin_Logo.png

Meaning I can access the image with the following code:

UIImage myImage = UIImage.FromFile("_Resources\Xamarin_Logo.png");

A short interlude

At this point, it is probably wise to diverge from the main point and do a little explaining… You see that I have named the folder “_Resources” and not “Resources” - there is a reason, I am not just being awkward. The folder name “Resources” is a reserved name, and MonoTouch will throw the following error at compile time if you name the folder “Resources”:

Resources/Xamarin_Logo.png: Error: The folder name ‘Resources’ is reserved and cannot used for Content files (ResourcesExample)

Doh… I solve this by adding an underscore to the beginning of the folder name. You could change this to “Images” or “Boyakasha” or, indeed, anything else you wanted, it would still work… Just don’t use a reserved name! (Boyakasha hasn’t been coined by the Mono compiler… yet)

Back to the point

My point is that, I am used to embedding images as resources into my .Net projects and accessing them as objects rather than as a string location to a directory. I think this is better because:

  • Strongly typed
  • I can change the Resource file, and all associated images will be changed at the same time
  • I can transform the image before showing it (e.g. resize, remove sharp corners to please the office health and safety officer etc.)
  • I do this by creating a static class in my project named “Resources”, which has the definition of each Image which I will use in my project as a static property of type UIImage.
public static UIImage XamarinLogo {
	get {
		return UIImage.FromFile("_Resources/Xamarin_Logo.png");
	}
}

This now means that, as long as I include the namespace of the static “Resources” class in my code, I can reference that image using “Resources.XamarinLogo”. Magic!

Check out the source code for an example of this being used in a MonoTouch.Dialog sample app.


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