Question

I want to add some functionality to existing (closed-source) applications on Android. For example: adding an item in the context-menu.

Is this possible? My guess is to hack my way into the Dalvik VM, but I can’t find any information about it.

Answer 1

Is this possible?

Generally, no. If the “existing (closed-source) applications” have an API that they publish and document, you are welcome to use such an API. Or, if the “existing (closed-source) applications” are leveraging so-called implicit Intent actions, like ACTION_SEND, you can simply support those interfaces.

For example, many applications have some sort of “share” menu item or button, which brings up a list of applications capable of sharing the content the original app wishes to share. This is accomplished via ACTION_SEND, and if you create an activity set up to respond properly to ACTION_SEND requests, your activity can appear in this list automatically, no hacking required.

My guess is to hack my way into the Dalvik VM

Fortunately, that will not work. You cannot “hack [your] way into the Dalvik VM” running in another process.