If you get the error of "Type R cannot be resolved to a variable" after Android SDK and ADT updated. Try to find and install any available update in Android SDK.
In my case, after update Android SDK Tools rev 22, and also ADT. I get error of "Type R cannot be resolved to a variable" in my projects, and any new project!
- Start Android SDK Manager again. Two more update available, Android SDK Platform-tools and Android SDK Build-tools. It was not available in the previous update.
- Install the update packages.
- Close and restart Eclipse.
- Problem solved.