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G E T S T R E A M . I O Becoming an Android Librarian

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G E T S T R E A M . I O skydoves @github_skydoves Android Developer Advocate @ Stream Jaewoong Eum

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G E T S T R E A M . I O Open-Source Libraries

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G E T S T R E A M . I O Open-Source Libraries

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G E T S T R E A M . I O Library & SDK Lifecycles Design Develop Prepare Release

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G E T S T R E A M . I O Library & SDK Lifecycles Design Develop Prepare Release Design process

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G E T S T R E A M . I O Library & SDK Lifecycles Design process 1. Define a problem 2. Research overall ideas 3. Verify the feasibility of your ideas 4. Investigate dependencies 5. Draw blueprints of application interfaces 6. Design the application interfaces

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G E T S T R E A M . I O Library & SDK Lifecycles Design Develop Prepare Release Development strategies

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G E T S T R E A M . I O Development Strategies Minimize API surfaces Module Public Interface

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G E T S T R E A M . I O Development Strategies Minimize API surfaces Client Client Client Client

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G E T S T R E A M . I O Development Strategies Minimize API surfaces Client Client Client Client

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G E T S T R E A M . I O Development Strategies Minimize API surfaces Client Client Client Client

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G E T S T R E A M . I O Development Strategies Minimize API surfaces Public Internal

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G E T S T R E A M . I O Development Strategies Minimize API surfaces Client Client Client Client Public Internal

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G E T S T R E A M . I O Development Strategies Minimize API surfaces Client Client Client Client

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G E T S T R E A M . I O Development Strategies Minimize API surfaces Client Client Client Client

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G E T S T R E A M . I O Development Strategies Minimize API surfaces private internal importance protected public

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G E T S T R E A M . I O Development Strategies Minimize API surfaces private internal importance protected public Client Client Client

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G E T S T R E A M . I O Development Strategies Minimize API surfaces class ApiResponseCallAdapter constructor( val resultType: Type ) : CallAdapter>> { override fun responseType(): Type { return resultType } override fun adapt(call: Call): Call> { return ApiResponseCallDelegate(call) } } Client

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G E T S T R E A M . I O Development Strategies Minimize API surfaces internal class ApiResponseCallAdapter constructor( private val resultType: Type ) : CallAdapter>> { override fun responseType(): Type { return resultType } override fun adapt(call: Call): Call> { return ApiResponseCallDelegate(call) } } Client

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G E T S T R E A M . I O Development Strategies Minimize API surfaces fun Context.dp2Px(dp: Int): Int { val scale = resources.displayMetrics.density return (dp * scale).toInt() } fun Context.px2Sp(px: Int): Int { val scale = resources.displayMetrics.scaledDensity return (px / scale).toInt() } val px = context.dp2Px(dp = 22) val sp = context.px2Sp(px = 22)

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G E T S T R E A M . I O Development Strategies Minimize API surfaces internal fun Context.dp2Px(dp: Int): Int { val scale = resources.displayMetrics.density return (dp * scale).toInt() } internal fun Context.px2Sp(px: Int): Int { val scale = resources.displayMetrics.scaledDensity return (px / scale).toInt() } val px = context.dp2Px(dp = 22) // Unresolved reference val sp = context.px2Sp(px = 22) // Unresolved reference

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G E T S T R E A M . I O Development Strategies Minimize API surfaces internal fun Context.dp2Px(dp: Int): Int { val scale = resources.displayMetrics.density return (dp * scale).toInt() } internal fun Context.px2Sp(px: Int): Int { val scale = resources.displayMetrics.scaledDensity return (px / scale).toInt() } int px = ContextExtensionKt.dp2Px(context, 11); int sp = ContextExtensionKt.px2Sp(context, 11);

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G E T S T R E A M . I O Development Strategies Minimize API surfaces @JvmSynthetic internal fun Context.dp2Px(dp: Int): Int { val scale = resources.displayMetrics.density return (dp * scale).toInt() } @JvmSynthetic internal fun Context.px2Sp(px: Int): Int { val scale = resources.displayMetrics.scaledDensity return (px / scale).toInt() } int px = ContextExtensionKt.dp2Px(context, 11); // Unresolved reference int sp = ContextExtensionKt.px2Sp(context, 11); // Unresolved reference

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G E T S T R E A M . I O Development Strategies Explicit API mode

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G E T S T R E A M . I O Development Strategies Explicit API mode

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G E T S T R E A M . I O Development Strategies Explicit API mode

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G E T S T R E A M . I O Development Strategies Explicit API mode

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G E T S T R E A M . I O Development Strategies Explicit API mode

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G E T S T R E A M . I O Development Strategies Binary Compatibility Validator

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G E T S T R E A M . I O Development Strategies Binary Compatibility Validator build.gradle module.gradle On terminal

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G E T S T R E A M . I O Development Strategies Binary Compatibility Validator module.api

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G E T S T R E A M . I O Development Strategies Binary Compatibility Validator

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G E T S T R E A M . I O Development Strategies Metalava

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G E T S T R E A M . I O Development Strategies Exposing resources /classes.jar /res/ /R.txt /public.txt /assets/ /libs/name.jar /jni/abi_name/name.so /proguard.txt /lint.jar /api.jar AAR file

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G E T S T R E A M . I O Development Strategies Exposing resources /classes.jar /res/ /R.txt /public.txt /assets/ /libs/name.jar /jni/abi_name/name.so /proguard.txt /lint.jar /api.jar AAR file res/drawable res/layout res/menu res/values res/xml res/raw res/anim res/animator res/mipmap res/font string.xml colors.xml styles.xml dimens.xml arrays.xml … /res/ /res/values/

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G E T S T R E A M . I O Development Strategies Exposing resources #FFFFFF #000000 #57A8D8 #FBC02D Library (colors.xml) Project val whiteColor = ContextCompat.getColor(this, R.color.white) binding.myView.setBackgroundColor(whiteColor)

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G E T S T R E A M . I O Development Strategies Exposing resources #FFFFFF #000000 #57A8D8 #FBC02D Library (colors.xml) val whiteColor = ContextCompat.getColor(this, R.color.white) binding.myView.setBackgroundColor(whiteColor) Project compile error!

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G E T S T R E A M . I O Development Strategies Exposing resources

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G E T S T R E A M . I O Development Strategies Exposing resources

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G E T S T R E A M . I O Development Strategies Exposing resources

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G E T S T R E A M . I O Development Strategies Exposing resources Project (XML) Project (code)

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G E T S T R E A M . I O Development Strategies Exposing resources Project (XML) Project (code)

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G E T S T R E A M . I O Development Strategies Exposing resources

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G E T S T R E A M . I O Development Strategies Exposing resources

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G E T S T R E A M . I O Development Strategies Exposing resources Library (layout_balloon.xml) Library (Balloon.Builder.kt)

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G E T S T R E A M . I O Development Strategies Exposing resources ● Some issues have been reported in Crashlytics. ● But the reports were not helpful at all. ● Occasionally the library behaves very weirdly. ● Also it’s really difficult to reproduce.

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G E T S T R E A M . I O Development Strategies Exposing resources Perhaps..?

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G E T S T R E A M . I O Development Strategies Exposing resources … Library (layout_balloon.xml) Project (layout_balloon.xml) ...

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G E T S T R E A M . I O Development Strategies Exposing resources … Library (layout_balloon.xml) // wrong behaviors Project (layout_balloon.xml) // runtime error! ...

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G E T S T R E A M . I O Development Strategies Resource prefix resourcePrefix

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G E T S T R E A M . I O Development Strategies Resource prefix resourcePrefix

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G E T S T R E A M . I O Development Strategies Resource prefix build.gradle

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G E T S T R E A M . I O Development Strategies Resource prefix layout_balloon.xml attrs.xml

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G E T S T R E A M . I O Development Strategies Resource prefix

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G E T S T R E A M . I O Development Strategies R class Non transitive R class

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G E T S T R E A M . I O Development Strategies Non transitive R class

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G E T S T R E A M . I O Development Strategies Non transitive R class

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G E T S T R E A M . I O Development Strategies Non transitive R class :app :library :material (MDC) implementation implementation

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G E T S T R E A M . I O Development Strategies Non transitive R class :app :library :material (MDC) com.google.android.material.R (:material) implementation implementation

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G E T S T R E A M . I O Development Strategies Non transitive R class :app :library :material (MDC) com.my.library.R (:material) (:library) com.google.android.material.R (:material) implementation implementation

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G E T S T R E A M . I O Development Strategies Non transitive R class :app :library :material (MDC) com.my.library.R (:material) (:library) com.google.android.material.R (:material) com.my.app.R (:material) (:library) (:app) implementation implementation

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G E T S T R E A M . I O Development Strategies Non transitive R class :app :library :material (MDC) Transitive dependency com.my.library.R (:material) (:library) com.google.android.material.R (:material) com.my.app.R (:material) (:library) (:app) implementation implementation

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G E T S T R E A M . I O Development Strategies Non transitive R class com.my.library.R (:material) (:library)

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G E T S T R E A M . I O Development Strategies Non transitive R class

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G E T S T R E A M . I O Development Strategies Non transitive R class :app :library :material (MDC) implementation implementation com.my.library.R (:material) (:library) com.google.android.material.R (:material) com.my.app.R (:material) (:library) (:app) Wow, a million of LoC in R classes in a minute!

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G E T S T R E A M . I O Development Strategies Non transitive R class Dex format has 64K limit for methods and fields references! 64K (65,536 = 64 x 1024 (2^10))

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G E T S T R E A M . I O Development Strategies Non transitive R class

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G E T S T R E A M . I O Development Strategies Non transitive R class android.nonTransitiveRClass=true gradle.properties

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G E T S T R E A M . I O Development Strategies Non transitive R class :app :library implementation implementation com.my.library.R (:library) com.google.android.material.R (:material) com.my.app.R (:app) Refer to its own resources without pulling resources from dependencies. nonTransitiveRclass :material (MDC)

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G E T S T R E A M . I O Development Strategies Non transitive R class Before After (enabled non transitive R class)

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G E T S T R E A M . I O Development Strategies Non transitive R class aar size diff 226054 bytes -> 214538 bytes (11516 bytes reduced) 10,000 end-users 2260540000 bytes -> 2145380000 bytes (≈115 MB reduced) 100,000 end-users 22605400000 bytes -> 21453800000 bytes (≈1.1 GB reduced) 1,000,000 end-users 226054000000 bytes -> 214538000000 bytes (≈10 GB reduced) 100,000,000 end-users 22605400000000 bytes -> 21453800000000 bytes (≈1 TB reduced)

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G E T S T R E A M . I O Development Strategies Non transitive R class :app :feature1 :feature2 :feature3 com.my.app.R (:feature1) (:feature2) (:feature3) (:app) Unresolved reference

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G E T S T R E A M . I O Development Strategies Non transitive R class :app :feature1 :feature2 :feature3 com.my.app.R (:feature1) (:feature2) (:feature3) (:app) full name package import with namespacing

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G E T S T R E A M . I O Library & SDK Lifecycles Design Develop Prepare Release

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G E T S T R E A M . I O Preparation Documentation (KDoc)

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G E T S T R E A M . I O Preparation Documentation (Dokka) ./gradlew dokkaHtml ./gradlew dokkaHtmlMultiModule ./gradlew dokkaJavadoc

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G E T S T R E A M . I O Preparation Documentation (README)

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G E T S T R E A M . I O Library & SDK Lifecycles Design Develop Prepare Release

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G E T S T R E A M . I O Release Maven

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G E T S T R E A M . I O Release Maven repositories mavenCentral() google() jcenter()

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G E T S T R E A M . I O Release Maven central repository 1. Registering a Sonatype account 2. Generating a GPG key pair 3. Setting up publication in your project a. Maven publishing setup with Gradle b. Signing artifacts with GPG key c. Configure pom files d. Per-module Gradle setup 4. Publish to sonatype repository 5. Evaluate and close the ticket on staging repositories

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G E T S T R E A M . I O Release Maven central repository 🔗 https://bit.ly/386yJt1

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G E T S T R E A M . I O Release Jitpack maven { url 'https://jitpack.io' }

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G E T S T R E A M . I O Library & SDK Lifecycles Design Develop Prepare Release Verification

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G E T S T R E A M . I O Verifying and Marketing Community

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G E T S T R E A M . I O Verifying and Marketing Technical contents

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G E T S T R E A M . I O Verifying and Marketing Example projects Codes speak louder than words!

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G E T S T R E A M . I O Blog Post 🔗 https://bit.ly/3Qim5ZB

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G E T S T R E A M . I O https://github.com/skydoves jaewoong.eum@getstream.io https://twitter.com/github_skydoves https://medium.com/@skydoves Contact

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G E T S T R E A M . I O Thank you.