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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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