Tools:
https://github.com/patrickfav/uber-apk-signer
https://github.com/iBotPeaches/Apktool
How:
apktool d app-release.apk -o extracted_apk
Tools:
https://github.com/patrickfav/uber-apk-signer
https://github.com/iBotPeaches/Apktool
How:
apktool d app-release.apk -o extracted_apk