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Don't be ashamed of your gradle.build files anymore Madis Pink, Droidcon Boston 2017

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Don't be ashamed of your gradle.build files anymore Madis Pink, Droidcon Boston 2017

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Don't be ashamed of your gradle.build files anymore Madis Pink, Droidcon Boston 2017

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Don't be ashamed of your build.gradle files anymore Madis Pink, Droidcon Boston 2017

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Don't be ashamed of your build.gradle files anymore Madis Pink, Droidcon Boston 2017

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I always end up googling for examples, and then modifying them until they coincidentally happen to do what I need1. 1 /u/sacundim commenting on Gradle. From Reddit.

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The principle of least surprise

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The fine print

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Standard Android Gradle project structure . ├── build.gradle ├── app │ └── build.gradle └── lib └── build.gradle

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Standard Android Gradle project structure . ├── build.gradle <-- root project ├── app │ └── build.gradle └── lib └── build.gradle

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Standard Android Gradle project structure . ├── build.gradle ├── app │ └── build.gradle <-- app (sub-)project └── lib └── build.gradle

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Standard Android Gradle project structure . ├── build.gradle ├── app │ └── build.gradle └── lib └── build.gradle <-- library (sub-)project

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Things you can do with the root project

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The buildscript classpath buildscript { repositories { jcenter() } dependencies { classpath 'com.android.tools.build:gradle:2.3.1' } } Make plugins and classes available to the project buildscript and all it's subprojects

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The buildscript classpath def buildTime = new Date().format("yyyy-mm-dd'T'HH:mm:ssZ") android { defaultConfig { buildConfigField "String", "BUILD_TIME", "\"${buildTime}\"" } }

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The buildscript classpath buildscript { repositories { jcenter() } dependencies { classpath 'com.android.tools.build:gradle:2.3.1' classpath 'joda-time:joda-time:2.9.9' } }

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The buildscript classpath import org.joda.time.DateTime // ... android { defaultConfig { // using joda-time in our buildscripts buildConfigField "String", "BUILD_TIME", "\"${DateTime.now()}\"" } }

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The buildscript classpath Only have the buildscript {} block in the root project

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ext (ExtraPropertiesExtension)

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ext (ExtraPropertiesExtension) In root: ext { compileSdk = 25 } In app/lib: android { compileSdkVersion rootProject.ext.compileSdk }

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ext (ExtraPropertiesExtension) In root: ext { supportLibVersion = '25.3.1' appCompat = "com.android.support:appcompat-v7:${supportLibVersion}" cardView = "com.android.support:cardview-v7:${supportLibVersion}" }

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ext (ExtraPropertiesExtension) In app/lib: dependencies { compile rootProject.ext.appCompat compile rootProject.ext.cardView }

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ext (ExtraPropertiesExtension) In app/lib: dependencies { compile appCompat compile cardView }

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Configuring multiple projects in one go

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Configuring multiple projects in one go In root: allprojects { println "In project ${path}" }

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Configuring multiple projects in one go In root: allprojects { println "In project ${path}" } $ ./gradlew help In project : In project :app In project :lib # ..help output omitted..

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Configuring multiple projects in one go allprojects { repositories { jcenter() } }

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Configuring multiple projects in one go allprojects { repositories { jcenter() maven { url "https://jitpack.io" } maven { url 'https://acmecorp.example.com/internal/repository' } } }

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Configuring multiple projects in one go allprojects { plugins.withId('com.android.application') { android { buildToolsVersion '25.0.2' compileSdkVersion 25 } } }

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Subproject gradle files

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Ordering within Gradle files import foo.Bar

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Ordering within Gradle files import foo.Bar apply plugin: 'foo'

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Ordering within Gradle files import foo.Bar apply plugin: 'foo' configurations { }

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Ordering within Gradle files import foo.Bar apply plugin: 'foo' configurations { } android { }

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Ordering within Gradle files import foo.Bar apply plugin: 'foo' configurations { } android { } dependencies { }

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Ordering within Gradle files import foo.Bar apply plugin: 'foo' configurations { } android { } dependencies { } task custom(type: CustomTask) { }

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Be consistent

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Do not repeat configuration blocks dependencies { compile rootProject.ext.appCompat } android { // like 300 lines of android config } dependencies { compile rootProject.ext.cardView }

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Organizing repetitive config

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Organizing repetitive config apply plugin: 'checkstyle' tasks.create("checkstyle", Checkstyle) { tasks.check.dependsOn it source 'src' include '**/*.java' configFile file("${rootDir}/checkstyle.xml") classpath = files() }

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Organizing repetitive config apply plugin: 'checkstyle' apply plugin: 'findbugs' tasks.create("checkstyle", Checkstyle) { tasks.check.dependsOn it source 'src' include '**/*.java' configFile file("${rootDir}/checkstyle.xml") classpath = files() } tasks.create("findbugs", FindBugs) { /* ... */ }

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Organizing repetitive config apply plugin: 'checkstyle' apply plugin: 'findbugs' apply plugin: 'pmd' tasks.create("checkstyle", Checkstyle) { tasks.check.dependsOn it source 'src' include '**/*.java' configFile file("${rootDir}/checkstyle.xml") classpath = files() } tasks.create("findbugs", FindBugs) { /* ... */ } tasks.create("pmd", Pmd) { /* ... */ }

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Organizing repetitive config apply from: "${rootDir}/quality.gradle"

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buildSrc

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buildSrc def gitHash(project) { def stdout = new ByteArrayOutputStream() project.exec { workingDir project.rootDir commandLine 'git', 'rev-parse', '--short', 'HEAD' standardOutput = stdout } return stdout.toString().trim() } // prints f559b99 println gitHash(project)

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buildSrc . ├── build.gradle ├── app │ └── build.gradle └── lib └── build.gradle

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buildSrc . ├── build.gradle ├── buildSrc <-- buildSrc meta-project │ └── src/main/groovy ├── app │ └── build.gradle └── lib └── build.gradle

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buildSrc/src/main/groovy package pink.madis.gradle class Git { static hash(project) { def stdout = new ByteArrayOutputStream() project.exec { workingDir project.rootDir commandLine 'git', 'rev-parse', '--short', 'HEAD' standardOutput = stdout } return stdout.toString().trim() } }

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buildSrc import pink.madis.gradle.Git // ... // prints f559b99 println Git.hash(project)

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buildSrc/src/main/java package pink.madis.gradle; import org.gradle.api.Project; import java.io.ByteArrayOutputStream; public class Git { public static String hash(Project project) { ByteArrayOutputStream stdout = new ByteArrayOutputStream(); project.exec(spec -> { spec.workingDir(project.getRootDir()); spec.commandLine("git", "rev-parse", "--short", "head"); spec.setStandardOutput(stdout); }); return stdout.toString().trim(); } }

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Java, yaaaay \o/

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buildSrc public class Deps { private static final String supportLibVersion = "25.3.1"; public static final String appCompat = "com.android.support:appcompat-v7:" + supportLibVersion; public static final String cardView = "com.android.support:cardview-v7:" + supportLibVersion; }

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buildSrc import pink.madis.gradle.Deps // ... dependencies { compile Deps.appCompat // <-- clickable & autocompletable compile Deps.cardView }

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Writing plugins

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Writing plugins package org.gradle.api public interface Plugin { void apply(T target) }

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Writing plugins package org.gradle.api public interface Plugin { void apply(Project target) }

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Writing plugins class CheckstylePlugin implements Plugin { @Override void apply(Project project) { project.with { // move the quality.gradle contents here } } }

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Writing plugins class CheckstylePlugin implements Plugin { @Override void apply(Project project) { project.with { apply plugin: 'checkstyle' tasks.create("checkstyle", Checkstyle) { tasks.check.dependsOn it source 'src' include '**/*.java' configFile file("${rootDir}/checkstyle.xml") classpath = files() } } } }

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Writing plugins project.with { apply plugin: 'checkstyle' } // same as project.apply plugin: 'checkstyle'

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Writing plugins class CheckstylePlugin implements Plugin { @Override void apply(Project project) { project.apply plugin: 'checkstyle' project.tasks.create("checkstyle", Checkstyle) { project.tasks.check.dependsOn it source 'src' include '**/*.java' configFile project.file("${rootDir}/checkstyle.xml") classpath = project.files() } } }

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Writing plugins public class CheckstylePlugin implements Plugin { @Override public void apply(Project project) { project.apply(Collections.singletonMap("plugin", "checkstyle")); project.getTasks().create("checkstyle", Checkstyle.class, task -> { project.getTasks().getByName("check").dependsOn(task); task.source("src"); task.include("**/*.java"); task.setConfigFile(new File(project.getRootDir(), "checkstyle.xml")); task.setClasspath(project.files()); }); } }

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Writing plugins replace apply from: "${rootDir}/quality.gradle" with apply plugin: pink.madis.gradle.CheckStylePlugin

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Writing plugins build.gradle ↓ quality.gradle ↓ CheckstylePlugin

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TL;DR → Use ext {} in root project to share constants

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TL;DR → Use ext {} in root project to share constants → Configure common things like repositories with allprojects {}

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TL;DR → Use ext {} in root project to share constants → Configure common things like repositories with allprojects {} → Extract common configuration to separate files (and eventually plugins)

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TL;DR → Use ext {} in root project to share constants → Configure common things like repositories with allprojects {} → Extract common configuration to separate files (and eventually plugins) → Take advantage of buildSrc

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TL;DR → Use ext {} in root project to share constants → Configure common things like repositories with allprojects {} → Extract common configuration to separate files (and eventually plugins) → Take advantage of buildSrc → Prefer Java where possible

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Thanks! Questions? Twitter: @madisp Slides: speakerdeck.com/madisp