Building next gen android library with gradle

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Building next-gen Android library with GradleAnton RutkevichAndroid developer

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About me

3+ years of Android developmentMobile game-dev experience

At Yandex:Android developmentContinuous Integration

At Google Developer Group Minsk:Co-organizerSpeaker

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Old-style library projects The past, the present…

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What’s wrong?

• Hard to update• Hard to distribute• Eclipse, eclipse…

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Gradle & The New Build SystemThe present, the future…

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Gradle - build automation evolved

• Build scripts on Groovy• Flexible build setup• Runs everywhere (Java required)• Dependency management

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Dependency management

• Maven artifacts• Local artifacts• Library projects

dependencies {compile

‘com.google.code.gson:gson:2.2.4’compile fileTree(dir: ‘libs’,

include: ‘*.jar’)

compile project(‘:my-library’)}

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The New Build System

• Brings Gradle features to Android builds

• Provides Android Studio integration

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.aar format

• Zip archive• Structure is similar to old-style library project

• /AndroidManifest.xml• /classes.jar• /res/• /R.txt• /assets/• /libs/*.jar• /jni/<abi>/*.so• /proguard.txt

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A good library

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Self sufficient

• plain java jar-file ?

• maven plain java jar?

• maven Android jar ?

- dependencies

+/- obfuscation

- AndroidManifest.xml

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Friendly

• Does not create conflicts with other

libraries

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Stable

• Behavior does not change over time

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Building next-gen Android libraryThe right way

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Key components

/AndroidManifest.xml/classes.jar/res//R.txt/assets//libs/*.jar/jni/<abi>/*.so/proguard.txt

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Resources

Lint will warn you!

android {resourcePrefix 'mylib_'

}

Use resource prefix for library resources

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Obfuscation. DON’Ts for library

-repackageclasses ‘’

-allowaccessmodification// hidden -> public

a.classb.class…

DEX

a.classb.class…

first.jar second.jar

error: duplicate class

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Obfuscation. Rules for users

Will be packaged into aar

defaultConfig {consumerProguardFiles ‘pro-consumer.txt’

}

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Dependencies. Stable vs dynamic versions

Stable versions give stable builds

dependencies {// 1.6.0 only compile

‘com.squareup.okhttp:okhttp:1.6.0’// Latest versioncompile ‘com.squareup.okhttp:okhttp:+’

}

Dynamic versions do not require redeploy

Use stable versions for library dependencies

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Dependencies. Maven only!

What’s wrong with local jars?

libs/ lib-1.0.jar

libs/ lib-1.0.jar

first.aar second.aar

DEX

error: duplicate class

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Manifest. Static values

Will be copies into app’s manifest file ‘as is’.

<uses-permission android:name="android.permission.INTERNET" />

<application><activity

android:name="com.my.app.SomeActivity”/></application>

Include required values only!

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Manifest. Dynamic values 1

defaultConfig {manifestPlaceholders

= [ userAppPackage: "\${packageName}” ]}

<uses-permission android:name="$

{userAppPackage}.LIB_PERMISSION" />

Library’s build.gradle

Library’s AndroidManifest.xml

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Manifest. Dynamic values 2

<uses-permission android:name="$

{packageName}.LIB_PERMISSION" />

Will give

in library’s aar AndroidManifest.xml

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Manifest. Dynamic values 3

Library’s aar AndroidManifest.xml

Application’s build.gradle

<uses-permission android:name="$

{packageName}.LIB_PERMISSION" />

defaultConfig {packageName = "com.my.app”

}

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How to use itdepending on your build system

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Case 1. Using Eclipse, etc

1. Unzip aar 2. Attach as library project3. Add classes.jar (and libs/) to classpath4. Add native libraries5. Add proguard entries6. …

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Case 2. Using Gradle & local aar

project-folder/build.gradlerepo/library-1.0.aar

repositories {flatDir { dirs ‘repo’ }

}dependencies {

compile ‘com.company:library:1.0@aar’}

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Case 3. Using Gradle & Maven

dependencies {compile ‘com.company:library:1.0’// orcompile ‘com.company:library:1.0@aar’

}

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What’s next?

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Uncovered topics

• Maven Central publication

• Multiple library variant generation

• Native libraries

• …

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Thank you for your attention!

Anton Rutkevich

antonrut@yandex-team.ruanton.rutkevich@gmail.com