8. Mobile Application Development with Android

Mobile applications backed by cloud-based RESTful services have emerged as the primary face of computing in terms of massive consumer participation. Jason Christensen described this system architecture in his OOPSLA 2009 presentation [http://www.slideshare.net/jasonc411/oopsla-2009-combining-rest-and-cloud-a-practitioners-report]. Therefore, not only do we find it important to cover this system architecture in the curriculum, but we also see this architecture as a very effective context for teaching various important computer science topics:

• (real-world) software architecture

  • dependency inversion principle (DIP)
  • model-view-adapter architectural pattern (MVA)
  • testability
  • etc.

• concurrent, parallel, and distributed computing topics (PDC/TCPP/EduPar)

  • events
  • timers (one-shot and recurring)
  • background threads
  • offloading tasks to the cloud

• embedded/resource-conscious computing

  • limitations of the device
  • capabilities of the device (numerous sensors)

Konstantin drew the inspiration to use Android instead of Swing as a context for teaching these topics from the mobile computing session at SIGCSE 2012 in Raleigh [http://www.sigcse.org/sigcse2012].

Furthermore, we have found the cost of switching from, say, Java Swing to Android minimal. Besides, Android matters in the real world: it is a widely used technology, and mobile app development skills are in increasing demand.

While our overall goals are similar to those of the Sofia framework project [http://sofia.cs.vt.edu/sofia-2114/book], we discuss here a language-based approach but are planning to enhance the practice of Android development in Scala through additional support classes.

As mentioned above, current and future focus has been on these courses:

• COMP 313/413: Intermediate Object-Oriented Development [http://laufer.cs.luc.edu/teaching/313] (focusing on software design and architecture), using Java with Android since fall 2012, considering the addition of Scala down the road
• COMP 373/473: Advanced Object-Oriented Development [http://laufer.cs.luc.edu/teaching/473], using Scala since spring 2010, planning to add Android in spring 2014

8.1. Tools

There are two sbt plugins for developing Android:

• https://github.com/pfn/android-sdk-plugin
• http://fxthomas.github.io/android-plugin

The rapidly evolving topic of developing Android apps in Scala is the subject of this discussion forum:

• https://groups.google.com/forum/#!topic/scala-on-android

After some experimentation, we have found pfn’s plugin [https://github.com/pfn/android-sdk-plugin] to be easier to use and have adopted it for our Scala-based Android development.

8.2. Examples

The learning objectives of each example are stated in the example’s readme.

• Clickcounter app [https://bitbucket.org/loyolachicagocs_plsystems/clickcounter-android-scala]
• Prime checker app [https://bitbucket.org/loyolachicagocs_plsystems/primenumbers-android-scala]
• Prime checker web service [https://bitbucket.org/loyolachicagocs_distributed/primenumbers-spray-scala]

8.3. Lab Assignment

Format

Pair project

Time

10 minutes

Deliverable

An enhancement of this clickcounter app [https://bitbucket.org/loyolachicagocs_plsystems/clickcounter-android-scala] that addresses at least one following additional functional requirements:

• New user story: a max (^) button as the analogous dual to the reset (0) button.
• Retaining application state during rotation (see here to find out how to rotate the emulator [http://stackoverflow.com/questions/3916096/android-avd-rotate-portrait-landscape-how]).

Nonfunctional requirements

• You should update the tests and the rest of the existing code accordingly.
• You should implement the onSaveInstanceState and onRestoreInstanceState application lifecycle methods (see [http://developer.android.com/guide/components/activities.html#SavingActivityState] for details. The system passes this method a Bundle in which you can save state information about the activity as name-value pairs, using methods such as putString() and putInt().