Is it advantageously to have multiple modules in an Android Studio Project over having only a single large app-module?
I know about Android Modules in general and the advantages of SOLID so my focus is especially considering build performance. As gradle can do incremental builds, and if only one module changes, those other modules don't need to be processed?
Is this noticeable or is there even a considerable amount of overhead?
A project with multiple Gradle modules is known as a multi-module project. In a multi-module project that ships as a single APK with no feature modules, it's common to have an app module that can depend on most modules of your project and a base or core module that the rest of the modules usually depend on.
Modules provide a container for your app's source code, resource files, and app level settings, such as the module-level build file and Android manifest file. Each module can be independently built, tested, and debugged. Android Studio uses modules to make it easy to add new devices to your project.
An Android library is structurally the same as an Android app module. It can include everything needed to build an app, including source code, resource files, and an Android manifest.
Wikipedia. You can think of modularization like turn some of your packages into small reusable pieces of code across your application. The modules you are going to create can be android libraries, pure kotlin/java libraries, more app modules, wearable modules, auto modules etc.
It is of great advantage to have multiple modules rather than to create a single large app-module. Following are the key points:
You can have a look for more on android developer resource
How modularization can speed up your Android app’s built time
App modularization and module lazy loading at Instagram and beyond
Modularizing Android Applications by Mauin
Survey on how Android developers were modularising their apps
There was an article on Medium yesterday, which exactly adresses my question:
https://medium.com/@nikita.kozlov/how-modularisation-affects-build-time-of-an-android-application-43a984ce9968#.at4n9imbe
tl;dr:
First and most important, the hypothesis was correct, modularising project can significantly speed up build process, but not for all configurations.
Second, if splitting is done in a wrong way, then build time will be drastically increased, because Gradle build both, release and debug version of library modules.
Third, working in test-driven way is much easier for a project with multiple modules, because building a small library module is way faster then the whole project.
Forth, doing many things in parallel slows down the build. So having more powerful hardware is a good idea.
Below you can find results of all experiments described in this article
Addressed at Google I/O '17: https://youtu.be/Hx_rwS1NTiI?t=23m17s
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