Continuous integration and delivery for Android apps

1266 words

Recently, I created a native Android app called Noice. It started out as a weekend project but as I began to write it from scratch, I found so many new things to learn. So the original goal that should have been achieved within two to three days, ended up taking one and a half weeks.

During this time period, I focused on four different goals

  • Creating a beautiful Android app to play background noises
  • Getting better at writing Kotlin code
  • Learning about automated testing of Android components
  • Setting up continuous integration and delivery to automate testing and ease the process of deployment

The fourth and the final goal is a topic of interest for developers in almost every field. This post doesn’t emphasise much on how to do it, rather it focuses on the concepts and techniques involved.

Continuous Integration

As usual, from Wikipedia:

In software engineering, continuous integration (CI) is the practice of merging all developers’ working copies to a shared mainline several times a day.

In a nutshell, Continuous Integration is a practice where a mainline copy of the source code is maintained, e.g., master branch in a git repo, and any developer who wants to make changes to mainline can acquire their own copy, e.g., by creating a new branch in a git repo, and work on it. Once the changes are made, developers need to make sure that all automated tests are passing, and then they can merge their changes to the mainline, e.g., by creating a pull request on GitHub.

To ensure consistent builds and agility in the workflow, it is often recommended automating software build process along with automated testing, using an online CI Environment such as Travis CI, Jenkins, or Circle CI, etc.

Continuous Delivery and Deployments

Again, from Wikipedia:

Continuous delivery is the ability to deliver software that can be deployed at any time through manual releases; this is in contrast to continuous deployment which uses automated deployments.

Continuous Delivery is a practice where maintainers can release software using a trigger, e.g., with a push of a button or perhaps a terminal command. To setup Continuous Delivery, Continuous Integration is a mandate.

Continuous Deployment builds on continuous delivery and ensures automated software release with every change to mainline. There are no explicit triggers here. Changes to mainline act as implicit triggers to ensure complete autonomy.

Moreover, Continuous deployments are physible in projects such as web applications where a user doesn’t need to manually update the software every time a new update is released since releases happen very often in this scenario. Due to this, Continuous Delivery is more practical in scenarios where the software needs to be manually updated by a user.

Continuous Integration for Android apps

Before moving on to the good stuff, Continuous integration is required to make sure we’re not in an integration hell, although it’s highly unlikely for projects of the size of Noice.

To setup Continuous Integration, I used Travis CI which is free for open source projects. Following is a gist of configuration for the CI job used to run automated tests, that runs on every commit to mainline.

  • Line 1: Specifies which stage is this in the whole CI pipeline.
  • Line 2, 3: Tells Travis CI to set an environment variable. In this case, the exported variable reflects the path at which the code coverage report will be generated.
  • Line 4: Tells Travis what script to run. In this case, it is to run automated tests using the Gradle build tool.
  • Line 5: Uploads the generated code coverage report to a hosted service called CodeCov.

With the above configuration, Travis runs automated unit tests for every change that is made to the mainline branch. If any test case is failing, Travis reports it back to the developer in order to fix it. You can check out the sample output of some failing test cases here and test cases themselves here!

I chose not to include a build job in my CI pipeline to get faster results because running automated tests on Android applications implicitly builds a test APK. But it doesn’t mean that you should do this too!

Continuous Delivery for Android apps

Like I said before, continuous deployments are not very practical in environments where users manually need to update the software. For this reason alone, I chose to work with Continuous Delivery in this project.

To setup Continuous Delivery, the first thing I did was to set up a fresh job in Travis CI that uses Fastlane to build and push APK to the Play Store.


Fastlane is a tool from Google to build Android or iOS apps and deploy them to App Store or Play Store with a single command. Of course, it needs its own configuration to perform these actions but it is fairly straight forward. Its documentation has a dedicated section on setting it up for Android deployments.

In addition to building applications, Fastlane can also be configured to automatically capture screenshots from apps and upload them to respective stores. I chose not to use this option because it required a lot of change in my existing setup and screenshots for Noice aren’t supposed to change very often.

I’m leaving out the install and setup instructions. Here’s the Fastfile

First lane, beta, uses a Gradle task to build the signed Android app. And then it uses Fastlane’s upload_to_playstore action to perform the deployment. The app is signed using Gradle and not Fastlane.

The second lane, production, doesn’t build any binaries. Instead, it promotes the latest beta version present on the Play Store to production using the track_promote_to parameter of upload_to_playstore action.

Configuring the deployment job for Travis

My Travis configuration for deployment job was fairly simple given Fastlane did all the heavy lifting of uploading built binaries to the Play Store.

  • Line 2-5: Encrypted environment variables that contain passwords for certificate that is used by Gradle to sign built Android app
  • Line 7, 8: Decrypts an encrypted tar archive that holds the signing certificate and a Google Service Account key to be used by Fastlane.
  • Line 9, 10, 12: Installs Fastlane in Travis environment
  • Line 14, 15: Figures out whether the current release is a beta release (explained later).
  • Line 16: Uses Fastlane to build the Android app and perform deployment
  • Line 17: Cleans up secure files

Above deployment job only runs if the Travis build was triggered when a git tag was pushed to GitHub. You may want to check out the full Travis configuration for the sake of clarity.

Release Trigger

As I mentioned before, Continuous Delivery needs an explicit trigger to perform deployments. In Noice, I used git tags as release triggers.

Whenever I want to release a new version of Noice to the Play Store, I create a new tag using git tag command, push it to GitHub and then Travis starts the CI pipeline to perform all the necessary actions.

I use the 0.0.0-rc format in tag names to release the current version to beta users. Here, rc means Release Candidate. 0.0.0 format is for releasing to production. This is what Line 14 and 15 determine in deployment job.


No matter what kind of project you’re working on, the concepts of Continuous Integration, Delivery, and Deployments are the same. Same CI tools are employed to perform all the actions, just with different build tools.

If you still have a few minutes to spare, please check out Noice on GitHub. If you like what you see, give it a thumbs-up. Alternatively, you can also rate it on the Play Store.