Notes - Build a Modular Android App Architecture (Google I/O'19)

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本記事は、Build a Modular Android App Architecture (Google I/O'19)の記事です。

Why Modularize your app?

• People can specialize in certain sections of the application
• Maintainability
  • grouping layouts based on features
• Faster compilation
• Faster CI
  • Only modified module and the modules that depend on that module need to be tested.
  • How we do it in AndroidX
    • Discover dependency graph
    • Find changed fines from Git History
    • Execute all testes of affected modules
    • URL: goo.gle/androidx-dependency-tracker
• Good for business
  • Smaller APKs using the Android App bundle
• Isolated feature testing

How to modularize?

Dynamic Feature Module

• App can't depend on modules; modules depend on app
• onDemand="false", onDemand="true"
• Feature Modularization

Layer modularization

• Plaid Features
  • Persistence
  • API client / Authentication
  • Custom Styling Library
  • Feed UI
  • Post UI

Isolation via modules

• api vs implementation
  • if module is provided through api all of the public api are available for all the modules depending on that module.
  • if module is provided through implementation then all the modules depending on that module cannot see any public api

Feature modularization

• Encapsulation
• Possibility for dynamic delivery

Layer modularization

• Isolation to your app
• Structure to your app

If you are starting from the monolithic app

• Start with layer modularization

Working with dynamic feature modules

• Navigation
  • starting activity
    • setClassName
  • starting fragment
  • Class.forName()..
    • Needs ProGuard
    • No runtime performance hits

=> Currently working on it with navigation jetpack library to make this navigation as natural as possible.

Databases

• One common database
  • Pros
    • Very easy to maintain database connection
    • Easy to share tables
  • Cons
    • No isolation between modules
    • Feature specific entities are in shared domain
• One database per module
  • Pros
    • Isolation between modules
  • Cons
    • Database connection maintenance
    • Duplicate data
• A hybrid approach

A bright feature with Room

• Multi-module databases with room
  • Separate databases combined at runtime
  • Cross-module database queries
• Not available yet

Android free modules

The benefits of it will be..

• Faster tests
• Minimize dependencies
• Separation of concerns
• Better abstractions

But do not do this if ..

• you don't have a use case for it / do not use it
• you don't have time; abstraction takes time

TL;DR

• Start re-writing your application in modules
• Just options
• Always keep your customers and users in your mind

所感・まとめ・個人的に印象に残ったことなど

• モジュール化することでCIでのテスト実行時間も短縮できそう
• DFM対応のプロジェクトの画面遷移の実装方法は、今後Navigation Architecture Componentsでより自然な形に改善されそう
• Roomには今後マルチモジュールを見据えた機能が追加されそう
• アーキテクチャが良いからという理由で☆5つをくれるユーザーはいないよ！何するにしてもユーザーのこと考えてね！が刺さった

以上です！