"R cannot be resolved to a variable"?
for me, the best solution to suggest to people that have problems with the "R" file would be to try the next steps (order doesn't matter) :
update ADT & SDK , Eclipse and Java (both 1.6 and the latest one).
EDIT: now the ADT supports Java 1.7 . link here.
remove gen folder , and create it again .
do a clean-project.
right click the project and choose android-tools -> fix-project-properties .
right click the project and choose properties -> java-build-path -> order-and-export. make sure the order is :
Android 4.4 (always the latest version)
Android private libraries
android dependencies
your library project/s if needed
yourAppProject/gen
yourAppProject/src
make sure all files in the res folder's subfolders have names that are ok : only lowercase letters, digits and underscore ("_") .
always make sure the targetSdk is pointed to the latest API (currently 19) , and set it in the project.properties file
try to run Lint and read its warnings. they might help you out.
make sure your project compiles on 1.6 java and not a different version.
restart eclipse.
Check your AndroidManifest.xml file, see if the package name is correct. If you copied an example it is likely this is wrong and the source of your problem.
1) see if the xml files in the Package Explorer tree have an error-icon if they do, fix errors and R-class will be generated.
example hint: FILL_PARENT was renamed MATCH_PARENT in API Level 8; so if you're targeting platform 2.1 (api 7), change all occurences back to "fill_parent"
2) if you added "import android.R;" trying to do a quick-fix, remove that line
I had the same problem. I didn't have any lines stating "import something.R". Cleaning and rebuilding also didn't solve the issue.
It turned out to be because of the name of a layout xml file. Those files can only contain lowercase letters, or numbers, or underscores. When I changed the filename (and everything that refers to it) from myLayout.xml to my_layout.xml, everything worked.