Nowadays, energy efficiency is recognized as a core quality attribute of applications (apps) running on Android-powered devices constrained by their battery. Indeed, energy hogging apps are a liability to both the end-user and software developer. Yet, there are very few tools available to help developers increase the quality of their native code by ridding it of energy-related bugs. Android Studio is the official IDE for millions of developers worldwide and there's no better place to enforce green coding rules in everyday projects. Indeed, Android Studio provides a code scanning tool called Android lint that can be extended with lacking green checks in order to foster the design of more eco-responsible apps.

1. Enforcing Green Code
With Android Lint
Olivier Le Goaer @ A-MOBILE 2020
- September 21, 2020 - Melbourne, Australia -

2. Context of Work
✗ Green Software
– Beyond fast-paced hardware advances, foster
development of energy-efficient software
✗ Mobile Software
– Battery-powered device non-connected to permanent
power (e.g. SmartPhone)
– Overconsumption of mobile apps implies more frequent
charges and ultimately battery depletion

3. Greenness is a matter of quality
✗ Poorly designed apps may drain the battery
excessively
✗ Greenness is a quality attribute that may be
statically checked by a lint tool
✗ Ultimately, the quality level reached by apps
should be rewarded by a green badge/score

4. Green Bugs within Android apps
✗ Green bugs are symptoms that something may
be wrong with the app's battery usage
✗ Android-specific green bugs are not classic
code smells merely applied to Android
– Refactoring of “God Class”, “God Method”, and “Feature
Envy” is even counterproductive*
* An Empirical Study on the Impact of Android Code Smells on Resource Usage, Oliveira et al., SEKE 2018

5. Catalog of Android Green Bugs
✗ Define a catalog of smells that have an actual
impact on power consumption
✗ Energy-related smells reside in an Android
project, not only in source code (.java/.kt)
✗ 13 green bugs were described in the paper. The
latest catalog describes 26 bugs
– http://green.pauware.com/android-lint/

6. The 13 Android Green Bugs
Name Severity Scope
Everlasting Service ERROR Source code
Sensor Leak ERROR Source code
Internet In The Loop ERROR Source code
Dark UI WARNING Manifest, Style, Drawable
Sensor Coalesce WARNING Source code
Durable Wake Lock WARNING Source code
Uncompressed Data
Transmission
WARNING Source code
Rigid Alarm WARNING Source code, Gradle
Dirty Boot WARNING Source code, Manifest
Keep Screen On INFORMATIONAL Source code, Layout
Keep CPU On INFORMATIONAL Source code, Manifest
Battery-Efficient Location INFORMATIONAL Source code, Gradle
Bluetooth Low-Energy INFORMATIONAL Source code

7. Keep Screen On (example)
« To avoid draining
the battery, an Android
device that is left idle
quickly falls asleep.
However, there are
times when an
application needs to
wake up the screen and
keep it awake to
complete some work. »
[Doc]
Programmatically (Java)
Declaratively (xml)

8. Android Lint Framework
✗ Extensible Framework : add custom checks to
the 350 built-in checks
✗ Jetbrain UAST = AST unifying Java and Kotlin
✗ Complete scan of an Android project (code,
ressources, manifest, …)
✗ Both on-the-fly and manual inspections within
Android Studio IDE

9. Greenness is not performance
✗ Power-saving may be a side effect of
performance, but not necessarily so
✗ Greenness merits its full-fledged category
NEW

10. Implementation details
✗ Green Bugs are issues in a registry
✗ Issues are reported by detectors
✗ A detector implements one or more scanners
✗ Visitor-style programming (in Java or Kotlin)
✗ Utils avoid doing things « the hard way »

11. Live demo: Dark UI

12. Research: what's next?
✗ Discovering unexplainable green bugs
– As opposed to the current green bugs that are explained
by the Android Reference Documentation
✗ Green bugs assessment at large scale
– Runtime testbed and automated UI test for millions of
apps is still a scientific challenge

13. Tooling: what's next?
Green Linter
Web-based Backend
(Green Quality Gates)
+
Gamification
Score 3/5

14. Summary
✗ Green coding habits should be rewarded
✗ Real-life Android development is predominantly
native, either in Java or Kotlin, with Android
Studio IDE
✗ Static analysis applies to and scales for any
app under development
✗ Android developers trust Android Lint

15. Thank you for
your attention
- Questions? -