I am trying to run Android sample applications using intellij idea and R.Java file is missing form notepad samples source directory.
Build -> Compile 'R.java'
or simply Ctrl+Shift+F9
.
In AndroidStudio use: Build -> Rebuild Project.
And remember, the generated R file is not in the project "gen" directory. It is in the "out" directory (drill down to your project).
Make sure you have the right settings: project structure -> Facets -> Android -> yourproject -> compiler
Check compile resources by IDE and Regenerate R.java when resources are changed.
This stole most of my morning, hopefully I'll save someone else some time:)
Use Build | Make. Actually, IDEA generates R.java file automatically every time you make a change in any XML file under the /res directory.
UPDATE: /gen directory must be present in the project and also configured as a Source root in IDEA module so that it can resolve the IDs in your source code.
If you are using IDEA 12 on Windows 7 (and probably Vista and 8), R.Java can be found at :
C:\Users\[username]\.IdeaIC12\system\compiler\[project].nnnnnnnn\.generated\aapt\[project].nnnnnnnn\production\[your\name\space]\R.java
Pay attention that, in current version of IDEA 12, the by-design behaviour is not to generate R.java in the generated sources project directory, but in an IDEA's system directory:
http://youtrack.jetbrains.com/issue/IDEA-99045
"It is behaviour of IDEA 12, it doesn't generate full R.java in gen folder, it generates it in the IDEA's system dir during compilation."
They intend to change this confusing behaviour, but if you're currently working in IDEA 12, look into ~/.IntelliJIdea12\system\compiler\YOUR_PROJECT_NAME.RANDOM_STRING\.generated\aapt\YOUR_PROJECT_NAME.RANDOM_STRING\production\package\R.java
for the actual generated source file.