Practical Modularisation for Android Developers

by Jordan Terry

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Practical modularisation for Android developers Jordan Terry 1

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Agenda ● Introduction ● What is modularisation? ● What is your codebase? ● Cohesion, Coupling & Gradle ● Build times ● Reusability ● Defining a strategy ● Questions? 2

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3 Introduction 🇹 Then Now 2015 2018 2021 @JordNullable

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What is modularisation? 4

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5 What is modularisation? Large system Modules

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7 Android modularisation Large System Modules Codebase Gradle Modules

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Talking about modularisation 8

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The beneﬁts of modularisation 9 Build Times Reusability

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What is your codebase? 10 ● Define a way to measure modularisation ● Apply that to your codebase

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11 Monolithic Modular What is your codebase? You are somewhere here…

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12 Monolithic Modular What is your codebase? = code base with a module that takes more time to compile than other modules = code base with no modules that take more time to compile than the sum of other modules

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What is your codebase? 13 Monolithic Modular

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14 Monolithic Very Modular What is your codebase? Modular

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Cohesion, Coupling & Gradle 16

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High Cohesion Low Cohesion Cohesion 17 Low Cohesion High Cohesion

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High Coupling Low Coupling Coupling 18 Low Coupling High Coupling

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Gradle 19 ● Module definition ● Connecting Modules ● Incremental Compilation

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20 import ':app' import ':login' import ':profile' import ':networking' import ':okhttp' settings.gradle.kts app/ -> login/ -> src/ -> build.gradle.kts -> profile/ -> src/ -> build.gradle.kts -> networking/ -> src/ -> build.gradle.kts -> okhttp/ -> src/ -> build.gradle.kts -> settings.gradle.kts app/ -> login/ -> src/ -> build.gradle.kts -> profile/ -> src/ -> build.gradle.kts -> networking/ -> src/ -> build.gradle.kts -> okhttp/ -> src/ -> build.gradle.kts -> settings.gradle.kts app/ -> login/ -> src/ -> build.gradle.kts -> profile/ -> src/ -> build.gradle.kts -> networking/ -> src/ -> build.gradle.kts -> okhttp/ -> src/ -> build.gradle.kts -> settings.gradle.kts app/ -> login/ -> src/ -> build.gradle.kts -> profile/ -> src/ -> build.gradle.kts -> networking/ -> src/ -> build.gradle.kts -> okhttp/ -> src/ -> build.gradle.kts -> settings.gradle.kts build.gradle.kts plugins { id("kotlin-android") } android { ... } dependencies { ... } Deﬁning Modules

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21 :networking :login :profile :okhttp :app Deﬁning modules

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dependencies { implementation project(":login") implementation project(":profile") } 22 app/build.gradle.kts Connecting modules

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23 :networking :login :profile :okhttp :app Connecting Modules

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:profile :profile 24 :profile Incremental compilation

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:login :profile :profile :login :networking :networking 25 :okhttp :app Incremental compilation

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The beneﬁts of modularisation 26 Build Times Reusability

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Incremental Build times 27 ● How important are build times? ● When incremental build times go wrong ● Some tips on cohesion

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XKCD 303 - https://xkcd.com/303/ 28 Build Times

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@vRallev on Twitter - https://mobile.twitter.com/vRallev/status/1485430862850125824 29 Build Times

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@softwarejameson on Twitter - https://twitter.com/softwarejameson/status/1455971162060697613?lang=en 30 Build Times

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Build times 600 engineers * $1.42/minutes * 42 builds/week * 44 work weeks/year = $1,600,000/year 31 Gradle vs Maven: Performance Comparison - https://gradle.org/gradle-vs-maven-performance/ Money Saved Equation

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:timelines :profile :login :network models 32 Build times - comparing structures :app :timelines :login :profile :networking :networking :network models

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:timelines :login :login models :profile models :timeline models :profile :networking 33 Build times - comparing structures :app :timelines :login :profile :networking :login models :profile models :timeline models :json

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Reusability 34 ● What are reusable components ● Reusable libraries ● Reusable modules

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Reusability 35 OkHttp Play Billing Toast API

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:timelines :profile :okhttp-4 :login Reusability - Third Parties 36 :timelines :login :profile :okhttp-3 :okhttp-4 :networking :networking :okhttp-3

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:navigation :navigation jetpack :navigation compose :login :timelines :timelines :login :profile :profile Reusability - APIs & Implementations 37 :navigation :api :navigation: impl compose :navigation: impl jetpack :navigation :impl

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A modularisation strategy 38 ● Training ● Discipline ○ Cohesion & Coupling

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Coming up with a plan 39 :foundation :feature :feature :feature :feature High Cohesion Low Coupling