How to create a license key as downloadable and test it on Android

Question

I am sure this is pretty simple, but I don’t know what to look for in order to get a short tutorial. I want to create an application and download it for free on the Android Market. Then I want to create one or more applications that are only license keys that open certain functions in a free application. What is the best way for a free app to check if there are paid apps on the device? Is there an easy way to check by package name, or do I need to create a content provider in paid applications that a free application can call to verify validity?

Or there may be some kind of global memory space (for example, preferences in the application) that all applications can read / write.

I know one solution that will work, and that I could easily implement - each paid application calls a web service the first time it starts and registers this IMEI phone. This will work, but requires Internet access, which may or may not be convenient for my application.

As with most Android issues, there is more than one way to get rid of a cat. I'm looking for what you guys think is the best (and safest) approach.

Answer 1

, "" . , , google.

, :

List<ApplicationInfo> list = context.getPackageManager().getInstalledApplications(PackageManager.GET_META_DATA);

ApplicationInfo, packageName .