Question

When developing Android applications in Eclipse often you will get errors asociated with the R file, like

R cannot be resolved to a variable  

or

id cannot be resolved or is not a field 

I am posting this question+answer to try to provide a complete and general look at the common mistakes an android beginner might encounter. If anyone thinks they can provide a better overview, or would like to add, edit or comment, feel free to do so.

Answer 1

There are basicaly 4 different things that could be wrong.

• there is an error in one of your resource xml files. This should be indicated either in Problems or in LintWarnings.
• a specific, but very common error, is that one of your resource files contains an improper character, namely capital letters.
• you are importing R.android, which is a collection of android’s own identifiers, not identifiers of your own resources.

If any of these are the cause of your problems. Do NOT import the R file. it’s located in the same package as the root of your project.

• However, another cause of the problem might be, that you have source code in different packages in your project.
  In that case you DO need to import mypackage.R or mypackage.*. Just like you would import any other class from a different package.