android - Create Free/Paid versions of Application from same code

Question

So I'm coming down to release-time for my application. We plan on releasing two versions, a free ad-based play-to-unlock version, and a paid fully unlocked version. I have the code set up that I can simply set a flag on startup to enable/disable ads and lock/unlock all the features. So literally only one line of code will execute differently between these versions.

In order to release two separate applications, they require different package names, so my question is this: Is there an easy way to refactor my application's package name? Eclipse's refactoring tool doesn't resolve the generated R file, or any XML references in layout and manifest files. I've attempted to make a new project using the original as source, but I can't reference the assets and resources, and I'm looking to avoid duplicating any of my code and assets. It's not a huge pain to refactor it manually, but I feel there must be a better way to do it. Anybody have an elegant solution to this?

Edit/Answered:

For my situation I find it perfectly acceptable to just use Project -> Android Tools -> Rename Application Package. I wasn't aware this existed, and I feel like an idiot for posting this now. Thanks for everyone's answers and comments, feel free to vote this closed.

Answer 1

It's very simple by using build.gradle in Android Studio. Read about productFlavors. It is a very usefull feature. Just simply add following lines in build.gradle:

productFlavors {
    lite {
        packageName = 'com.project.test.app'
        versionCode 1
        versionName '1.0.0'
    }
    pro {
        packageName = 'com.project.testpro.app'
        versionCode 1
        versionName '1.0.0'
    }
}

In this example I add two product flavors: first for lite version and second for full version. Each version has his own versionCode and versionName (for Google Play publication).

In code just check BuildConfig.FLAVOR:

if (BuildConfig.FLAVOR == "lite") {
   // add some ads or restrict functionallity

}

For running and testing on device use "Build Variants" tab in Android Studio to switch between versions: