Multiple APK's Interacting with each other

Question

Recently I came across a few apps (such as Clockworkmod's Rom Manager) where in order to get the pro version you had to download another APK. However once this APK was downloaded Rom Manager automatically knew this APK existed and added new functionality's. For example another app is the Astro app in which you can extend it by downloading modules from the Market.

Now I know how to check for the existence of another app, and I also know how to interact between apps via services. However my question is,it seemed like Clockwork and these other apps are using different apks for a plug-in type architecture. How does one do that? Have they predefined an entire plugin architecture and service model so whenever a new apk is installed the main app can check if its a module and call commands on it? Or is there something else going on?

Answer 1

I think these apps just know their plugins and how to use them. Plugins are separated to save some space or to add paid functionalities to free apps. Note that there are no 3rd party plugins to these apps - all of them was created by apps authors.

Actually I think it is technically possible to create real plugin system for Android apps. You could search for installed plugins using broadcast receivers, then talk with them through some API. However adding extensibility through plugins isn't trivial task, so I don't think it makes much sense to create such apps for mobile devices.