In this project, I created an app with multiple flavors that uses multiple libraries and Google Cloud Endpoints. The finished app consists of four modules. A Java library that provides jokes, a Google Cloud Endpoints (GCE) project that serves those jokes, an Android Library containing an activity for displaying jokes, and an Android app that fetches jokes from the GCE module and passes them to the Android Library for display.
As Android projects grow in complexity, it becomes necessary to customize the behavior of the Gradle build tool, allowing automation of repetitive tasks. Particularly, factoring functionality into libraries and creating product flavors allow for much bigger projects with minimal added complexity.
I learnt the role of Gradle in building Android Apps and how to use Gradle to manage apps of increasing complexity. I learnt to:
- Add free and paid flavors to an app, and set up your build to share code between them
- Factor reusable functionality into a Java library
- Factor reusable Android functionality into an Android library
- Configure a multi project build to compile your libraries and app
- Use the Gradle App Engine plugin to deploy a backend
- Configure an integration test suite that runs against the local App Engine development server
This is the starting point for the final project, which is provided to me in the course repository. It contains an activity with a banner ad and a button that purports to tell a joke, but actually just complains. The banner ad was set up following the instructions here:
https://developers.google.com/mobile-ads-sdk/docs/admob/android/quick-start
(You may need to download the Google Repository from the Extras section of the Android SDK Manager.)
My first task was to create a Java library that provides jokes. Create a new Gradle Java project either using the Android Studio wizard, or by hand. Then introduce a project dependency between my app and the new Java Library.
I made the button display a toast showing a joke retrieved from your Java joke telling library.
Created an Android Library containing an Activity that displays a joke passed to it as an intent extra. Wired up project dependencies so that the button can passes the joke from the Java Library to the Android Library.
This next task was be pretty tricky. Instead of pulling jokes directly from our Java library, I had to set up a Google Cloud Endpoints development server, and pull our jokes from there.
(I followed instructions from here: https://github.com/GoogleCloudPlatform/gradle-appengine-templates/tree/master/HelloEndpoints)
I introduced a project dependency between the Java library and the GCE module, and modifid the GCE starter code to pull jokes from the Java library. Then I created an Async task to retrieve jokes. Made the button kick off a task to retrieve a joke, then launch the activity from your Android Library to display it.
Added code to test that your Async task successfully retrieves a non-empty string.
Added free and paid product flavors to your app. Removed the ad (and any other irrelevant dependencies) from the paid flavor.
To tie it all together, I create a Gradle task that:
- Launches the GCE local development server
- Runs all tests
- Shuts the server down again
- Project contains a Java library for supplying jokes
- Project contains an Android library with an activity that displays jokes passed to it as intent extras.
- Project contains a Google Cloud Endpoints module that supplies jokes from the Java library. Project loads jokes from GCE module via an async task.
- Project contains connected tests to verify that the async task is indeed loading jokes.
- Project contains paid/free flavors. The paid flavor has no ads, and no unnecessary dependencies.
- App retrieves jokes from Google Cloud Endpoints module and displays them via an Activity from the Android Library.