I try to understand how a .apk file is built from source code. I know that with Android Studio or with the command gradlew the build can be done easily. The Android Sdk provides multiple tools that are used to build a .apk, which most of them I know what they do:
d8: java byte code to dalvik bytecode
aapt2: Compile resources and link them. This tool creates a .apk file of compiled resources. (It also creates R.java to reference the resources in the code.)
apksigner: Takes the .apk and signs it. Otherwise, it cannot be installed on an Android device.
zipalign: aligns uncompressed data of the .apk
The last two tools are used on the apk, which already contains all files. What I do not understand is how compiled code and compiled resources are combined? Before aapt2 was a thing the packaging was done with aapt, but it is not even listed on Androids Documentation. However, aapt is still in the Android Sdk build-tools. The new aapt2 has no option for packaging.
So, the question is which command-line tools and in which order are used to create a complete .apk from source code? Thank you!
EDIT: What I am looking for would be similar to this, where a .apk is created with the command-line step by step. Only the answer uses the old aapt, which I think is not used anymore.
EDIT 2:
Thanks to Allen Shaw for giving me the missing information. I was now able to compile an app with aapt2. The answer to my question was simply to zip the aapt2 output and the classes.dex.
You may also use aapt2 command
aapt2 link -o output.apk
reference the google document here
Add .dex file into apk:
zip -ur app-debug.apk classes.dex