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Understanding
Gradle for Android
Kevin Pelgrims
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About me
• Mobile Developer at Drivr
• Just launched Forward
• Working with Android since 2011
• .NET developer in a previous life
• Big interest in web technology
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Schedule
• The build file
• Groovy basics
• Back to the build file
• Custom tasks
• Tasks for Android
• Tips and tricks
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The build file
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The build file
apply plugin: 'com.android.application'
android {
compileSdkVersion 23
buildToolsVersion "23.1.0"
defaultConfig {
applicationId "com.muchgradle"
}
}
dependencies {
compile 'com.android.support:appcompat-v7:23.1.0'
}
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Groovy basics
To get Gradle, you need to get Groovy
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Verbosity
System.out.println("Hello, Java");
println("Hello, Java");
println("Hello, Java")
println "Hello, Java"
println 'Hello, Groovy'
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Dynamic typing
String name = "Andy"
def name = 'Andy'
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String interpolation
def name = 'Andy'
def greeting = "Hello, $name"
def name_size = "Your name is ${name.size()} characters long"
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Methods
public int square(int num) {
return num * num;
}
square(2);
def square(def num) {
num * num
}
square 4
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Closures
def square = { num ->
num * num
}
square 8
Closure square = {
it * it
}
square 16
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Closures
void runClosure(Closure closure) {
closure()
}
runClosure({ println 'Yo!'})
runClosure() { println 'Yo!'}
runClosure { println 'Yo!'}
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Lists
List list = [1, 2, 3, 4, 5]
list.each { element ->
println element
}
list.each { println it }
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Maps
Map map = [one:1, two:2, three:3]
map.get('one')
map['two']
map.three
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Maps
void print(Map args, String message) {
println args
println message
}
print(one:1, two:2, three:3, 'hello')
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The build file
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Back to the build file
apply plugin: 'com.android.application'
android {
compileSdkVersion 23
buildToolsVersion "23.1.0"
defaultConfig {
applicationId "com.muchgradle"
}
}
dependencies {
compile 'com.android.support:appcompat-v7:23.1.0'
}
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Back to the build file
apply plugin: 'com.android.application'
project.apply([plugin: 'com.android.application']);
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Back to the build file
dependencies {
compile 'com.android.support:appcompat-v7:23.1.0'
}
project.dependencies({
add('compile', 'com.android.support:appcompat-v7:23.1.0', {
// Configuration statements
});
});
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Back to the build file
android {
compileSdkVersion 23
buildToolsVersion "23.1.0"
defaultConfig {
applicationId "com.muchgradle"
}
}
Android plugin:
https://developer.android.com/tools/building/plugin-for-gradle.html
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Custom tasks
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Gradle build lifecycle
Initialization
Discover all modules
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Gradle build lifecycle
Initialization
Configuration
Configure project objects
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Gradle build lifecycle
Initialization
Configuration
Execution
Execute selected tasks
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Defining a task
task hello {
doLast {
println 'Hello, world!'
}
}
task hello << {
println 'Hello, world!'
}
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Defining a task
task hello {
println 'Configuration'
doLast {
println 'Goodbye'
}
doFirst {
println 'Hello'
}
}
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Ordering task actions
task hello {
doFirst { println 'Not really first' }
doFirst { println 'First' }
doLast { println 'Not really last' }
doLast { println 'Last' }
}
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Ordering tasks (1)
task task1 << {
println 'Task 1'
}
task task2 << {
println 'Task 2'
}
task2.mustRunAfter task1
> gradlew task2 task1
task1
task2
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Ordering tasks (2)
task task1 << {
println 'Task 1'
}
task task2 << {
println 'Task 2'
}
task2.dependsOn task1
> gradlew task2
task1
task2
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Android tasks
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Hooking into the Android plugin
android.applicationVariants.all { variant ->
println variant
}
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Hooking into the Android plugin
task hello << {
println 'Hello'
}
android.applicationVariants.all { variant ->
variant.assemble.dependsOn hello
}
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Automatically renaming APKs
android.applicationVariants.all { variant ->
variant.outputs.each { output ->
}
}
def file = output.outputFile
output.outputFile = new File(file.parent,
file.name.replace(".apk", "${variant.versionName}.apk"))
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Tips and tricks
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The Gradle Wrapper
• It’s there by default
• It’s everywhere
• It’s always the right version
• You can use different versions of Gradle for different projects
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Speeding up the build
• Use the latest version of Gradle
distributionUrl=https\://services.gradle.org/distributions/
gradle-2.8-all.zip
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Speeding up the build
• Use the latest version of Gradle
• Change your Gradle properties
org.gradle.parallel=true
org.gradle.daemon=true
org.gradle.jvmargs=-Xms256m -Xmx1024m
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Speeding up the build
• Use the latest version of Gradle
• Change your Gradle properties
• Build modules separately
gradlew :app:build :moduledirectoryname:build
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Speeding up the build
• Use the latest version of Gradle
• Change your Gradle properties
• Build modules separately
• Exclude modules from the build
gradlew assemble -x :libraryproject:assemble
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Speeding up the build
• Use the latest version of Gradle
• Change your Gradle properties
• Build modules separately
• Exclude modules from the build
• Do some profiling
gradlew task --profile
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Optimizing the APK
• ProGuard
android {
buildTypes {
release {
minifyEnabled true
proguardFiles getDefaultProguardFile
('proguard-android.txt'), 'proguard-rules.pro
...
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Optimizing the APK
• ProGuard
• Automatic resource shrinking
android {
buildTypes {
release {
minifyEnabled true
shrinkResources true
...
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Optimizing the APK
• ProGuard
• Automatic resource shrinking
• Manual resource shrinking
android {
defaultConfig {
resConfigs "en", "da", "nl"
}
}
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Optimizing the APK
• ProGuard
• Automatic resource shrinking
• Manual resource shrinking
android {
defaultConfig {
resConfigs "hdpi", "xhdpi", "xxhdpi", "xxxhdpi"
}
}
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Resources
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Resources
• Groovy SDK
• http://www.groovy-lang.org/download.html
• Gradle DSL
• https://docs.gradle.org/current/dsl/
• Android plugin documentation
• https://developer.android.com/tools/building/plugin-for-gradle.html
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Resources
I wrote a book!
https://www.packtpub.com/
application-development/gradle-
android
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Understanding
Gradle for Android
twitter.com/kevinpelgrims
google.com/+kevinpelgrims
kevinpelgrims.com