Is it possible to hack an app by reverse engineering the apk?

Question

I have learned from this post Reverse engineering from an APK file to a project that it is possible to get the java files from an apk. Does this mean a hacker can see my code?

Answer 1

Yes, but if seeing your code makes your app less secure, then your app's security model was flawed from the beginning. Any code or data that users shouldn't have access to should be run or stored only on your server, not on the users' devices.

Also, beware of snake oil obfuscators that claim to make it impossible to reverse-engineer your code. None of these work; anything your device can execute can be reverse-engineered with enough effort (except maybe SGX, but that doesn't exist on phones).