The resources in an Adroid APK file are compressed and stored in binary format.
Apktool (https://ibotpeaches.github.io/Apktool/) is an instrument for reverse engineering 3rd party, closed, binary Android apps. It can decode resources to its original form.
You may use this website to extract and research assets and the manifest file. To produce Java source code, try Android apk decompiler
Please, only use it for legitimate purposes.
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