A Healthy Dose of Gradle

Chicago Roboto 2017

Gradle is the official build system for Android but few ever go beyond editing dependencies or copy-pasting code from stackoverflow. However, it is possible to have a build that is both fast and tailored to your needs.

This session aims to make you a better developer by taking back control of your build.

We will be covering concepts like the build phases (Initialization, Configuration, Execution), the task graph and the plugins that are available for you. We will look at how to extend an existing build by creating custom tasks, developing our own simple plugins and learning how to debug and test them. And since no one likes a slow build, we will use the Gradle Profiler to troubleshoot performance problems and talk about the usual root causes for neverending builds.

Transcript

1. A Healthy Dose of Gradle Philippe Breault @pbreault
2. Intro • Google Developer Expert Android • Software Engineer @ American Express* • Android since 2010 * Opinions and views on products, services and/or resources expressed in this presentation are mine alone and do not necessarily reflect the views of my employer.
4. Title
5. Build from Eclipse •Needs a developer to build •Build process was in someone’s head •Environment can change
6. Release Checklist •Clean workspace •Change version •Create tag •Run Tests •etc
7. Never send a human to do a machine’s job
8. Ant •Codify the build process •Execute sequentially at will •It could be run on CI <project> <target name="clean"> <delete dir="build"/> </target> <target name="compile"> <mkdir dir="build/classes"/> <javac srcdir="src" destdir="build/classes"/> </target> <target name="jar"> <mkdir dir="build/jar"/> <jar destfile="build/jar/HelloWorld.jar" basedir="build/classes"> <manifest> <attribute name="Main-Class" value="oata.HelloWorld"/> </manifest> </jar> </target> <target name="run"> <java jar="build/jar/HelloWorld.jar" fork="true"/> </target> </project>
9. Shortcomings •XML •Variants/application id •Need to install ant •No dependency management
10. Shortcomings Completely separated from the IDE
11. Gradle to the rescue Groovy based
12. Gradle to the rescue Gradle Wrapper
13. Gradle to the rescue Android Studio Tooling Api Gradle Linked to the IDE
14. Understanding
15. Inputs Gradle Outputs
16. Project task task task task task
17. task (action) Inputs Outputs
18. compileJava *.java *.class
19. Plugins Gradle Android Plugin Java Plugin
41. Nice Features • Manifest Entries • AAR support • Add resources • Add java fields
42. Build Variants Flavor + Build Type == Variant e.g. paidDebug, paidRelease
43. Build Variants assembleDemoDebug assembleFullDebug assembleDemoRelease assembleFullRelease
44. Build Lifecycle Init Configure Execute setup multi project runs the gradle script, creates tasks run tasks
45. Build Lifecycle 1. Run settings.xml 2. Add build.gradle 3. Add app/build.gradle 4. Run build.gradle 5. Run app/build.gradle 6. Generates tasks 5. Run the task Init Configure Execute Root !"" app # $"" build.gradle !"" build.gradle $"" settings.gradle
46. Extending
47. task hello { doLast { println "Hello World"} } $./gradlew hello :hello Hello World BUILD SUCCESSFUL Total time: 0.584 secs
48. Groovy methods don’t need semi colons or parentheses System.out.println(“Hello World”); println(“Hello World”); println(“Hello World) println “Hello World”
49. Closures doLast({ println "Hello World" }) doLast() { println "Hello World" } doLast { println "Hello World" }
50. task hello { doLast { println "Hello World"} }
51. The documentation
52. task hello { doLast { println “Hey there” } } task goodbye(dependsOn: hello) { doLast { println “See ya" } } $./gradlew goodbye :hello Hey There :goodbye See ya BUILD SUCCESSFUL Total time: 0.713 secs
53. Map Literals def map = new HashMap() map.put(“firstName", "Philippe") map.put("lastName", "Breault") def map = [firstName: "Philippe", lastName:"Breault"]
54. Named Arguments def printStuff(Map params) { println params.firstName println params.lastName } printStuff(firstName: "Philippe", lastName: "Breault") apply plugin: 'com.android.application'
55. task goodbye(dependsOn: hello) { doLast { println "goodbye" } } Named Arguments
57. task clean(type: Delete) { delete buildDir }
59. Available Tasks •Copy •Delete •Sync •Jar •Ant •Exec •zip •FindBugs •Etc
60. $ ./gradlew greet :greet Hello everyone! BUILD SUCCESSFUL Total time: 0.731 secs task greet(type: GreeterTask) { whom = "everyone" }
61. class GreeterTask extends DefaultTask { public String whom = "world" @TaskAction def greet() { println "Hello $whom!" } }
62. // copy text files and upper case their content task uppercase(type: UpperCaseTask) { source = "src/main/resources" }
63. class UpperCaseTask extends DefaultTask { def source = "src/main/resources" def destination = "${project.buildDir}/uppercased" @TaskAction def upperCaseAllTheThings() { project.file(source).listFiles().each { original -> def target = new File(project.file(destination), original.name) target.parentFile.mkdirs() target.text = original.text.toUpperCase() } }
64. Where is the good old ‘UP-TO-DATE’ ? :uppercase BUILD SUCCESSFUL Total time: 0.666 secs
65. If inputs haven’t changed, the task is considered up to date Task Inputs Outputs
66. // Inputs @Input @InputFile @InputDirectory // Outputs @OutputFile @OutputFiles @OutputDirectory @OutputDirectories Annotate your inputs and outputs
67. class UpperCaseTask extends DefaultTask { def source = "src/main/resources" @InputDirectory File getSource() { project.file(source) } def destination = "${project.buildDir}/capitalized" @OutputDirectory File getDestination() { project.file(destination) } @TaskAction def upperCaseAllTheThings() { getSource().listFiles().each { original -> def target = new File(getDestination(), original.name) target.text = original.text.toUpperCase() } } }
68. ./gradlew uppercase :uppercase UP-TO-DATE BUILD SUCCESSFUL Total time: 0.644 secs
69. class UpperCaseTask extends DefaultTask { def source = "src/main/resources" @InputDirectory File getSource() { project.file(source) } def destination = "${project.buildDir}/uppercased" @OutputDirectory File getDestination() { project.file(destination) } @TaskAction def execute(IncrementalTaskInputs input) { // …. } }
70. @TaskAction def execute(IncrementalTaskInputs input) { input.outOfDate { changed -> println "${changed.file.name} is out of date" def targetFile = new File(getDestination(), changed.file.name) targetFile.text = changed.file.text.toUpperCase() } input.removed { removed -> println("${removed.file.name} was removed") new File(getDestination(), removed.file.name).delete() } }
71. Keep your build as clean as your production code
72. Organizing your Code In you build.gradle
73. Organizing your Code
74. Organizing your Code buildSrc
75. Plugins Making your build declarative
76. $./gradlew shout :shout YO YO YO WORLD! BUILD SUCCESSFUL Total time: 0.763 secs apply plugin: ShouterPlugin shouter { message = "yo yo yo world!" }
77. class ShouterPlugin implements Plugin<Project>{ @Override void apply(Project project) { project.extensions.create("shouter", ShouterPluginExtension) project.task('shout') { doLast { println project.shouter.message.toUpperCase() } } } } class ShouterPluginExtension { public String message }
78. class ShouterPlugin implements Plugin<Project>{ @Override void apply(Project project) { project.extensions.create("shouter", ShouterPluginExtension) project.task('shout') { doLast { println project.shouter.message.toUpperCase() } } } } class ShouterPluginExtension { public String message }
80. Profiling
81. ./gradlew assembleDebug --profile Built-in profiler
82. ./gradlew assembleDebug --profile Built-in profiler
83. Gradle build scan
84. Gradle build scan
85. Gradle Profiler
86. # Scenarios are run in alphabetical order clean_build { tasks = [":app:assembleDemoDebug"] cleanup-tasks = ["clean"] } incremental_java_file_change { tasks = [":app:assembleDemoDebug"] apply-non-abi-change-to = "app/src/main/java/com/developerphil/androidapp/MainActivity.java" } incremental_parallel_java_file_change { tasks = [":app:assembleDemoDebug"] gradle-args = ["--parallel", "--offline"] apply-non-abi-change-to = "app/src/main/java/com/developerphil/androidapp/MainActivity.java" }
88. Quick Wins TL;DR The less gradle has the do, the faster it will be
89. Don’t set dynamic values in the build config object buildConfigField 'String', 'GIT_SHA', "\"${readGitSha()}\"" buildConfigField 'String', 'BUILD_DATE', "\"${parseDate()}\""
90. Don’t run what you don’t need E.g. don’t make assembleDebug depend on check
91. Don’t configure what you don’t need // ./gradlew assembleDebug -DfastBuild=true ext.fastBuild = (System.getProperty("fastBuild", "false").toBoolean()) if (!ext.fastBuild) { apply plugin: ShouterPlugin shouter { message = "yo yo yo world!" } }
92. Use the parallel mode # Gradle.properties org.gradle.parallel=true # Or use: # ./gradlew assembleDebug --parallel
93. Reviewing
94. Gradle • Based on Groovy • Projects & tasks • Plugins
95. Read the Documentation • Google for • Gradle DSL • Gradle Android DSL
96. Keep it Clean • Use the buildSrc folder • Use plugins • Limit the imperative code in your build
97. Profile your build • Use ./gradlew —profile • Build scan • Gradle Profiler
98. Philippe Breault @pbreault The End