'R cannot be resolved to a variable' - gen folder is empty

Question

I\'ve got an error:

R cannot be resolved to a variable

in line:

setContentView(R.layout.main);

but I can\'t r

Answer 1

Make sure that you are extending Activity class

Answer 2

What you really need to do it just install "build-tools" from sdk manager, and r.java will be generated automatically in gen folder :)

Answer 3

Check your res/ folder in order to be sure that every file it contains has no error. If any error exists R can not be generated.

Answer 4

Clean your project once. It should build that file again automatically. Go to Project->Clean Of course, it will work ony if your xml files are syntactically correct!

Answer 5

Simple

Check that you have the same SDK - build version with your AndroidManifest and project.properties version.

Answer 6

Try this: comment setContentView(R.layout.main); and the build/clean your project again. Then uncomment the commented line. This issue should not be seen then.