An APK file is a package that contains all the code and resources of a software program. It includes the assets directory with the application's assets, an arsc file with precompiled resources such as strings, colors, or styles, and the application manifest. The resources are compiled with the asset packaging tool and its output is an APK file with all the resources except the code. The Java code generated with the APK is assigned a unique ID, allowing it to use the resource during compilation.
The APK file format was created so that developers could deliver software to devices in a single compressed file. The APK Analyzer provides the file browser with file sizes and their relative percentage of the total APK size. Apktool is a comprehensive solution for dismantling Android applications that have more functions than the APK Analyzer. It allows you to edit disassembled data and convert it back into a functional APK file.
The biggest benefit of using Apktool is the ability to edit this disassembled data and convert it back into a functional APK file. It also ensures that all the uncompressed data in the APK file is aligned with a four-byte limit to improve runtime performance when accessing large binary data, such as images. The final APK file can be used for testing (debugging builds) or can be published in the wild, either through a distribution platform such as Google Play, or as a standalone APK package that users can download secondarily. Although APKs can be obtained from the Google Play Store, there are several reasons why you might need to extract them from the applications that you have installed on your device.