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State of the union

The purpose of this document is to give anyone who reads it a quick overview of both the current state and the direction of the code. The community should try and update this document as the code evolves.

How we got here

  • App originally built in Java for Android 1.0/T-Mobile G1
  • Written at Google by graduate student interns and then University of Washington
  • Designed as a survey application backed by JavaRosa (which deals with XForm forms) communicating with OpenRosa servers
  • Many different contributors/styles/eras over 10+ year lifetime
  • App wasn't built with a TDD workflow or with automated testing
  • Lots of work in the last few years to add more tests and clean up code using coverage measurement and static checks

Where we are now

  • App written in a mixture of Java and Kotlin
  • App has mixture of unit tests (JUnit), Robolectric tests (Junit + Robolectric) and Espresso tests but coverage is far from complete
  • UI is "iconic" (old) but with a lot of inconsistencies and quirks and is best adapted to small screens (although often used on tablets)
  • A lot of code lives in between one "god" Activity (FormEntryActivity) and a process singleton (FormController)
  • Core form entry flow uses custom side-to-side swipe view (in FormEntryActivity made up of ODKView)
  • Questions are rendered using a view "framework" of implementations inheriting from QuestionWidget (which is documented at in WIDGETS.MD)
  • Async/reactivity handled with a mixture of callbacks, LiveData and Rx
  • App stores data in flat files indexed in SQLite
  • Access to data in SQLite happens through repository objects which deal in data/domain objects (FormsRepository and Form for example)
  • Settings for the app use Android's Preferences abstraction
  • App uses Material Theming so Material components are preferred over custom or platform ones.
  • Dagger is used to inject "black box" objects such as Activity and just uses a very basic setup
  • Http is handled using OkHttp3 and https client abstractions are generally wrapped in Android's AsyncTask (and some Rx)
  • Geo activities use three engines (Mapbox, osmdroid, Google Maps) depending on the selected basemap even though Mapbox could do everything osmdroid does
  • Code goes through static analysis using CheckStyle, PMD, ktlint and Android Lint
  • Forms get into the app from three different sources (Open Rosa servers, Google Drive and disk) but the logic for this is disparate and they don't sit behind a common interface
  • Instances are linked to the forms they are instances of through formid and version. However, the same formid and version combination could represent multiple forms in storage
  • SharedPreferences is wrapped in app's own Settings abstraction

Where we're going

  • General effort to increase test coverage and quality while working on anything and pushing more for tests in PR review
  • Slowly moving responsibilities out of FormEntryActivity
  • Writing pretty much all new code in Kotlin
  • Writing new code using a multi-module approach (feature modules, mini frameworks etc) and breaking old code out into modules when opportunities come up
  • Trying to remove technical debt flagged with @Deprecated
  • Replacing Rx (and other async work such as AsyncTask) with LiveData + Scheduler abstraction
  • Gradually removing use of CursorLoader (all remaining uses are in CursorLoaderFactory)