is it even possible to modify .apk, by adding additional class to .dex and re-packing with modified manifest.xml??

Question

is it even possible to modify .apk, by adding additional class to .dex and re-packing with modified manifest.xml??

I know there are tools such as baksmali / smali to disassemble / re-assemble given classes.dex from .apk, but not sure limitation what could be modified from there on?

I'm trying to add additional activity, to modify starting launcher activity (may be from androidmanifest.xml) from original apk, then re-pack and sign to make complete single .apk... all need to be done out of build time, no raw source or build structure visible, only .apk as input... ANY IDEA?

Answer 1

Yes, the tools you mentioned (baksmali/smali) help you to both disassemble apks and modify and repackage the code later.

However, signing the modified apk in a way to make it update-compatible is unfeasible unless you have access to the private key that was used to sign the original apk.