Out of technical curiosity, I wanted to inspect the internals of an Android app. I'm well acquainted with being able to download and inspect iOS apps on the Mac, so I was interested in how I might be able to perform the same task with an Android app and a Mac. Finding the answer proved to be a little more convoluted than I initially expected.
There are several tools and esoteric methods to try and download an APK to a Mac, but my initial cursory attempt did not meet with immediate success, so I investigated other routes. There are many options to transfer standard files (photos, documents, etc.) to and from an Android device using the venerable Android File Transfer app, but that did not allow the capability to transfer an app from the phone onto the computer.
I was already familiar with using adb to sideload an app onto an Android device, so I figured that the reverse might be a feasible solution. Indeed, this is possible. This took a couple of steps from the command line to copy the apk (named myapp in this example) onto the Mac.
- Get a list of all of the packages available on the device:
adb shell pm list packages - Search for the identifier of the app you want and run the following command to get its path:
adb shell pm path com.example.myapp - Finally, copy the apk file to the selected destination on your computer:
adb pull /data/app/com.example.myapp-1/base.apk path/to/destination/
Similar to how an iOS app's ipa file is just a loosely disguised zip file, the same applies to the apk file. One can use a simple command of unzip myapp.apk to dump the contents of the apk file for further inspection. However, some of the files, such as the XML files, might be saved in a binary format, so it is not read as easily as an unencrypted text file. This was a good start, but some further work was needed to be able to more thoroughly explore the package's contents.
Android Studio can also be used to open up an APK, but since I did not have that installed on my laptop, I opted for the recommended tool apktool. However, if you have Android Studio already available, that is the ideal route to take.
I installed a current version of Java and the apktool. Once it was in place, I was able to extract the contents of the APK using the command apktool d myapp-base.apk. This dumps the contents of the apk into a separate folder, making the xml files, assets and other support files readable.
I hope that this small tutorial proves useful for anyone else who is also interested in being able to take an app from an Android device, put it on a computer, and then inspect its contents to see how an app was constructed. Happy exploring!