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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 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

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G E T S T R E A M . I O Library & SDK Lifecycles Design process 1. Define the problem 2. Research overall solutions 3. Verify the feasibility of the solutions 4. Define dependency relationships 5. Draw blueprints of the final usage in real-world projects 6. Design the interfaces

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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 Development Strategies Minimize API surfaces

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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

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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 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) } }

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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) } }

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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 public.xml

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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

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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 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) implementation implementation com.google.android.material.R (:material)

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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)

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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)

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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 Transitive dependency com.my.library.R (:material) (:library) com.google.android.material.R (:material) com.my.app.R (:material) (:library) (:app)

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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 :material (MDC) 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.

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

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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 projects 2260540000 bytes -> 2145380000 bytes (≈115 MB reduced) 100,000 projects 22605400000 bytes -> 21453800000 bytes (≈1.1 GB reduced) 1,000,000 projects 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 mavenCentral()

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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 🔗 https://bit.ly/3KU3Xk4

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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 Management

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G E T S T R E A M . I O Management Code formatting

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G E T S T R E A M . I O Management Code formatting

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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 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.