Building Android Apps with Gradle

Gradle • Build automation tool, builds upon Maven and Ant • Uses build.gradle files for configuration ! PROTIP • Use the gradle wrapper http://www.gradle.org/

Gradle android plugin Build with `./gradlew clean assemble` ! Android Tasks • assemble • clean • connectedCheck • deviceCheck • check • build ! ./gradlew tasks --all http://tools.android.com/ tech-docs/new-build-system/ user-guide

Basic App Structure Project ├── app │ ├── build.gradle │ ├── keystore │ ├── libs │ │ └── *.jar │ └── src └── build.gradle

Top level build file Project ├── app │ ├── build.gradle │ ├── keystore │ ├── libs │ │ └── *.jar │ └── src └── build.gradle Add configuration options common to all sub-projects/modules. ! task wrapper(type: Wrapper) { gradleVersion = '1.8' }

Module build file Main application build file. It would contain information such as dependencies, plugins, etc. With the Android plugin, you can define additional properties for your application, such as package name, version code, etc. Project ├── app │ ├── build.gradle │ ├── keystore │ ├── libs │ │ └── *.jar │ └── src └── build.gradle

Sample build.gradle for an Android app https://github.com/f2prateek/android-device-frame- generator/blob/master/app/build.gradle

Basic App Structure My build.gradle is configured to pick up all jars in this folder. Use this for dependencies not available via published repositories. ! compile fileTree(dir: 'libs', include: '*.jar') . ├── app │ ├── build.gradle │ ├── keystore │ ├── libs │ │ └── *.jar │ └── src └── build.gradle

Sources Project ├── app │ ├── build.gradle │ ├── keystore │ ├── libs │ │ └── *.jar │ └── src └── build.gradle

Sources │ └── src │ ├── debug │ │ └── AndroidManifest.xml │ ├── instrumentTest │ │ ├── AndroidManifest.xml │ │ └── java │ ├── main │ │ ├── AndroidManifest.xml │ │ ├── java │ │ └── res │ └── release │ ├── AndroidManifest.xml │ └── res │ └── values │ └── analytics.xml

Main Source Set │ └── src │ ├── debug │ │ └── AndroidManifest.xml │ ├── instrumentTest │ │ ├── AndroidManifest.xml │ │ └── java │ ├── main │ │ ├── AndroidManifest.xml │ │ ├── java │ │ └── res │ └── release │ ├── AndroidManifest.xml │ └── res │ └── values │ └── analytics.xml The default source set. Stick to this if you want no build customization.

Instrument Tests Source Sets │ └── src │ ├── debug │ │ └── AndroidManifest.xml │ ├── instrumentTest │ │ ├── AndroidManifest.xml │ │ └── java │ ├── main │ │ ├── AndroidManifest.xml │ │ ├── java │ │ └── res │ └── release │ ├── AndroidManifest.xml │ └── res │ └── values │ └── analytics.xml

Build Types │ └── src │ ├── debug │ │ └── AndroidManifest.xml │ ├── instrumentTest │ │ ├── AndroidManifest.xml │ │ └── java │ ├── main │ │ ├── AndroidManifest.xml │ │ ├── java │ │ └── res │ └── release │ ├── AndroidManifest.xml │ └── res │ └── values │ └── analytics.xml The Android plugin gives you release and debug configurations for free. Simply create a source folder for each configuration and get started with basic build customization.

Build Types Some added tasks: • assembleDebug • assembleRelease ! ./gradlew assembleRelease OR ./gradlew aR Each configuration creates some appropriate corresponding tasks.

Android Configuration defaultConfig { minSdkVersion 14 targetSdkVersion 19 packageName "com.f2prateek.dfg" versionCode versionMajor * 10000 + versionMinor * 1000 + versionPatch * 100 + versionBuild versionName "${versionMajor}.${versionMinor}.${versionPatch}" buildConfig """\ public static final int VERSION_MAJOR = ${versionMajor}.; """ } def versionMajor = 2 def versionMinor = 0 def versionPatch = 0 def versionBuild = 1

Android Configuration This sample : • Defines minSdkVersion and maxSdkVersion • Defines package name • Defines version code and version name • Adds version name to BuildConfig (access it with BuildConfig.VERSION_MAJOR, no need for a Context!). Next version of the build tools will have more information out of the box, such as package name, version name, version code, etc.

Customizing Builds debug { packageNameSuffix ".debug" versionNameSuffix "-debug" } release { signingConfig signingConfigs.release }

Customizing Builds This sample : • Adds a suffix to the package name for debug build types • Adds a suffix to the version name for debug build types • Configures release build types to use a signing configuration that is shown in the next slide

Customizing Builds : Merging • All build types share code from the main source set • The manifest is merged into the app manifest • The code acts as just another source folder • The resources are overlayed over the main resources, replacing existing values

Customizing Builds : Uses • Permissions in debug mode only, but not in release mode • Custom implementation for debugging • Different resources for debug mode (for instance when a resource value is tied to the signing certificate)

Custom Build Types beta.initWith(buildTypes.release) beta { versionNameSuffix "-beta" } sourceSets.beta.setRoot('src/release') This creates a custom build type named ‘beta’, initializing it from the properties of the release build type. By default, it would have it’s source set under ‘src/beta’. Here I manually set the source set to be under ‘src/ release’. The only difference between the two versions in my case is that beta has a suffix in it’s version name.

Signing packages signingConfigs { release { storeFile file("keystore") storePassword "notYourRealPassword" keyAlias "keystore" keyPassword "notYourRealPassword" } } task askForPasswords << { def storePassword = new String(System.console().readLine("\n\$ Enter keystore password: ")) def keyPassword = new String(System.console().readLine("\n\$ Enter key alias password: ")) android.signingConfigs.release.storePassword = storePassword android.signingConfigs.release.keyPassword = keyPassword } ! tasks.whenTaskAdded { theTask -> if (theTask.name.equals("validateReleaseSigning")) { theTask.dependsOn "askForPasswords" } }

Signing packages This uses a file ‘keystore’ with an alias ‘keystore’. It asks for a password for both via the command line. Alternatively, you can make it pick up system properties, or pick them up in a file like signing.properties

Renaming the .apk file applicationVariants.all { variant -> apk = variant.packageApplication.outputFile; newName = apk.name.replace(".apk", "-v${defaultConfig.versionName}-${versionBuild}.apk"); newName = newName.replace("app", "${defaultConfig.packageName}"); variant.packageApplication.outputFile = new File(apk.parentFile, newName); if (variant.zipAlign) { variant.zipAlign.outputFile = new File(apk.parentFile, newName.replace("-unaligned", "")); } }

Renaming the .apk file Produces the following apk’s • com.f2prateek.dfg-beta-unaligned-v2.0.0-1.apk • com.f2prateek.dfg-beta-v2.0.0-1.apk • com.f2prateek.dfg-debug-unaligned-v2.0.0-1.apk • com.f2prateek.dfg-release-unaligned-v2.0.0-1.apk • com.f2prateek.dfg-release-v2.0.0-1.apk

Checkstyle (thank Jake Wharton!) apply plugin: 'checkstyle' ! checkstyle { configFile project.file('../checkstyle.xml') showViolations true } ! android.applicationVariants.all { variant -> def name = variant.buildType.name def checkstyle = project.tasks.create "checkstyle${name.capitalize()}", Checkstyle checkstyle.dependsOn variant.javaCompile checkstyle.source variant.javaCompile.source checkstyle.classpath = project.fileTree(variant.javaCompile.destinationDir) checkstyle.exclude('**/BuildConfig.java') checkstyle.exclude('**/R.java') project.tasks.getByName("check").dependsOn checkstyle }

Checkstyle for library projects apply plugin: 'checkstyle' ! checkstyle { configFile project.file('../checkstyle.xml') showViolations true } ! android.libraryVariants.all { variant -> def name = variant.buildType.name def checkstyle = project.tasks.create "checkstyle${name.capitalize()}", Checkstyle checkstyle.dependsOn variant.javaCompile checkstyle.source variant.javaCompile.source checkstyle.classpath = project.fileTree(variant.javaCompile.destinationDir) checkstyle.exclude('**/BuildConfig.java') checkstyle.exclude('**/R.java') project.tasks.getByName("check").dependsOn checkstyle }

Sample of Manifest in release, debug and main https://github.com/f2prateek/ android-device-frame-generator