Learn Dynamic Code Loading (DCL)

We recently designed and implemented a new Android library that eases the proper implementation of Android apps that rely on dynamic code loading (DCL).

With this experiment, we want to determine whether our work actually helps Android developers! Your help will be incredibly useful to evaluate and improve our research effort!

This experiment is structured in two parts. First, we will ask you to implement a specific functionality using one of the standard Android API (no worries, we will provide all the details later! :-)). Second, we will ask you to implement the same functionality, using the new library we designed.

Our goal is to evaluate how our library helps an Android developer in writing a functionality based on dynamic code loading. We are currently interested in evaluating several aspects, such as efficiency, code readability, security, and maintainability of the code.

For this experiment, we will give you a toy application to play with, and we will ask you to implement several additional functionalities (again, all the details later). Note: Even if the application is not a real, full-fledge Android app, we ask you to treat such app as if it would be your most successful app on the Google official app store, with millions of users!

Again, you will play with a toy example, but, for the purpose of this experiment, treat as it were real! We stress this point as playing a toy app might lead you to write sloppy/hacky code. This, unfortunately, will invalidate the results of this experiment! So, once again, be ready to write code you can be proud of!! :-)

Alright, let's start!

Requirements

Double check that you are set with these tools:

1. Android Studio + Gradle: You must have a working version of this IDE installed on your machine. In the case that you do not, you can get the latest running version by following instructions reported here.

2. Git: In order to move properly between the different branches that I have set up, you will need this version control system. Grab the latest version of it here; in case you are completely new to Git, you may prefer to first become confident with it before moving on. On the net you may find several good tutorials for Git, a cool one is Try Git but there are just so many of them..

Phase 1

You will practice how to use the DexClassLoader class by filling in the missing parts in a simple skeleton application, in order to download code from a remote location and execute it.

Note: do not read/continue to Phase 2 until you are done with this one! No spoilers!

Here is a walk through on what you are expected to do:

• Clone this repository on your local machine by typing the following command in a terminal.

    $ git clone https://github.com/lukeFalsina/learnDCL.git

• Create a first branch called dcl and invoke checkout on it to change branch. You will use this branch to save your first implementation of the sample app project.

    $ cd learnDCL
    $ git branch dcl
    $ git checkout dcl

• Open the project contained in the root folder with Android Studio.
• Read carefully the class MainActivity.java in the app module. Parts of the code are purposely missing: I expect you to implement them :) Follow the step-by-step instructions in the comments of the Java class to understand exactly what to do. Please bear in mind that you are expected to write a secure, working application.
• Perform this simple "Repack" test:
  • Run your working app as it is now and see how it behaves.
  • Once done, modify the string APK_CONTAINER_URL inside the MainActivity.java class from its current value to

    https://dl.dropboxusercontent.com/u/28681922/HelperAppRepack.apk

* Save and run again the application.
* Can you spoil any difference between the two executions? What is the
  final outcome in this second test case compared to the first one?

• Once done, just commit your changes (git commit) on your LOCAL machine (so, no git push) and remember (or even write down) the outcome of the previous "Repack" test since we will ask you about it later on.

Phase 2

For this phase, we will ask you to implement a very similar functionality, this time by using our new library! The library you will need to use is called Grab'n run (GNR), which is available at http://www.grabnrun.org.

Here are the details on how to continue!

• Now checkout the secure branch and then create a new branch called securedcl. This new branch will record your second implementation of the example application.

    $ git checkout secure
    $ git branch securedcl
    $ git checkout securedcl

• If you turn back your attention to the Android Studio editor, you will notice that the code that you have just implemented vanished and it was substituted by a different implementation of the MainActivity.java class.

• Now go through the comments to understand exactly what you are supposed to do. Basically, you will now implement the same application you did before but this time you will learn how to use Grab'n Run (GNR) APIs instead of the native DexClassLoader APIs.

• Once your app works correctly again, perform the same "Repack" test explained before.

  • Can you notice any difference between this execution of the test and the one that you did before? If yes, awesome ;)

• Once more, remember to commit and keep in mind the outcome of the second run of the "Repack" test.

Phase 3

In addition to your code, we would like to be able to re-construct your build files. So:

• Zip your "learnDCL" folder and send it to lfalsina@gmail.com (To speed up the process, before compressing the folder, you may clean the builds from your project. To achieve this, simply type and execute in the same terminal you used before ./gradlew clean).
• Complete this form on your experiment with DCL and Grab'n Run.

Thanks in advance for your time playing with this tutorial and I hope you enjoyed it!

In case you get stuck or you have questions and/or suggestions, you are more than welcome to contact me by email :)

Happy coding :D

Luca