Руководство по gradle

Contents

1. 1 Introduction
   1. 1.1 Why Gradle?
   2. 1.2 Requirements
2. 2 Basic Project Setup
   1. 2.1 Simple build files
   2. 2.2 Project Structure
      1. 2.2.1 Configuring the Structure
   3. 2.3 Build Tasks
      1. 2.3.1 General Tasks
      2. 2.3.2 Java project tasks
      3. 2.3.3 Android tasks
   4. 2.4 Basic Build Customization
      1. 2.4.1 Manifest entries
      2. 2.4.2 Build Types
      3. 2.4.3 Signing Configurations
3. 3 Dependencies, Android Libraries and Multi-project setup
   1. 3.1 Dependencies on binary packages
      1. 3.1.1 Local packages
      2. 3.1.2 Remote artifacts
   2. 3.2 Multi project setup
   3. 3.3 Library projects
      1. 3.3.1 Creating a Library Project
      2. 3.3.2 Differences between a Project and a Library Project
      3. 3.3.3 Referencing a Library
      4. 3.3.4 Library Publication
4. 4 Testing
   1. 4.1 Unit testing
   2. 4.2 Basics and Configuration
   3. 4.3 Resolving conflicts between main and test APK
   4. 4.4 Running tests
   5. 4.5 Testing Android Libraries
   6. 4.6 Test reports
      1. 4.6.1 Multi-projects reports
   7. 4.7 Lint support
5. 5 Build Variants
   1. 5.1 Product flavors
   2. 5.2 Build Type + Product Flavor = Build Variant
   3. 5.3 Product Flavor Configuration
   4. 5.4 Sourcesets and Dependencies
   5. 5.5 Building and Tasks
   6. 5.6 Multi-flavor variants
   7. 5.7 Testing
   8. 5.8 BuildConfig
   9. 5.9 Filtering Variants
6. 6 Advanced Build Customization
   1. 6.1 Running ProGuard
   2. 6.2 Shrinking Resources
   3. 6.3 Setting language level

If you are looking for a full list of options available in build.gradle files, please see the DSL reference.

The goals of the new build system are:

• Make it easy to reuse code and resources
• Make it easy to create several variants of an application, either for multi-apk distribution or for different flavors of an application
• Make it easy to configure, extend and customize the build process
• Good IDE integration

Gradle is an advanced build system as well as an advanced build toolkit allowing to create custom build logic through plugins. Here are some of its features that made us choose Gradle:

• Domain Specific Language (DSL) based on Groovy, used to describe and manipulate the build logic
• Build files are Groovy based and allow mixing of declarative elements through the DSL and using code to manipulate the DSL elements to provide custom logic.
• Built-in dependency management through Maven and/or Ivy.
• Very flexible. Allows using best practices but doesn’t force its own way of doing things.
• Plugins can expose their own DSL and their own API for build files to use.
• Good Tooling API allowing IDE integration

Requirements

Basic Project Setup

A Gradle project describes its build in a file called build.gradle located in the root folder of the project. (See Gradle User Guide for an overview of the build system itself.)

Simple build files

buildscript {
    repositories {
        jcenter()
    }

    dependencies {
        classpath 'com.android.tools.build:gradle:1.3.1'
    }
}

apply plugin: 'com.android.application'

android {
    compileSdkVersion 23
    buildToolsVersion "23.1.0"
}

There are 3 main areas to this Android build file:

buildscript { … } configures the code driving the build. In this case, this declares that it uses the jCenter repository, and that there is a classpath dependency on a Maven artifact. This artifact is the library that contains the Android plugin for Gradle in version 1.3.1. Note: This only affects the code running the build, not the project. The project itself needs to declare its own repositories and dependencies. This will be covered later.

Then, the

com.android.application plugin is applied. This is the plugin used for building Android applications.

Finally,

android { … } configures all the parameters for the android build. This is the entry point for the Android DSL. By default, only the compilation target, and the version of the build-tools are needed. This is done with the compileSdkVersion and buildtoolsVersion properties.

The compilation target is the same as the target property in the project.properties file of the old build system. This new property can either be assigned a int (the api level) or a string with the same value as the previous target property.

Important: You should only apply the

com.android.application plugin. Applying the java plugin as well will result in a build error.

Note: You will also need a local.properties file to set the location of the SDK in the same way that the existing SDK requires, using the

sdk.dir property.
Alternatively, you can set an environment variable called ANDROID_HOME. There is no differences between the two methods, you can use the one you prefer. Example local.properties file:

Inside each of these directories there are subdirectories for each source component. For both the Java and Android plugin, the location of the Java source code and the Java resources are:

• java/
• resources/

For the Android plugin, extra files and folders specific to Android:

• AndroidManifest.xml
• res/
• assets/
• aidl/
• rs/
• jni/
• jniLibs/

This means that *.java files for the main source set are located in src/main/java and the main manifest is src/main/AndroidManifest.xml

Note: src/androidTest/AndroidManifest.xml is not needed as it is created automatically.

Configuring the Structure

android {
    sourceSets {
        main {
            manifest.srcFile 'AndroidManifest.xml'
            java.srcDirs = ['src']
            resources.srcDirs = ['src']
            aidl.srcDirs = ['src']
            renderscript.srcDirs = ['src']
            res.srcDirs = ['res']
            assets.srcDirs = ['assets']
        }

        androidTest.setRoot('tests')
    }
}

• assemble
  The task to assemble the output(s) of the project.
• check
  The task to run all the checks.
• build
  This task does both assemble and check.
• clean
  This task cleans the output of the project.

The tasks assemble, check and build don’t actually do anything. They are «anchor» tasks for the plugins to add dependent tasks that actually do the work.

This allows you to always call the same task(s) no matter what the type of project is, or what plugins are applied. For instance, applying the findbugs plugin will create a new task and make check depend on it, making it be called whenever the check task is called.

From the command line you can get the high level task running the following command:

Running the build task twice without making changes to your project, will make Gradle report all tasks as UP-TO-DATE, meaning no work was required. This allows tasks to properly depend on each other without requiring unnecessary build operations.

Here are the two most important tasks created by the java plugin, dependencies of the main anchor tasks:

• assemble
• jar
  This task creates the output.
• check
• test
  This task runs the tests.

The jar task itself will depend directly and indirectly on other tasks: classes for instance will compile the Java code. The tests are compiled with testClasses, but it is rarely useful to call this as test depends on it (as well as classes).

In general, you will probably only ever call assemble or check, and ignore the other tasks. You can see the full set of tasks and their descriptions for the Java plugin here.

Android tasks

The Android plugin uses the same convention to stay compatible with other plugins, and adds an additional anchor task:

• assemble
  The task to assemble the output(s) of the project.
• check
  The task to run all the checks.
• connectedCheck
  Runs checks that requires a connected device or emulator. they will run on all connected devices in parallel.
• deviceCheck
  Runs checks using APIs to connect to remote devices. This is used on CI servers.
• build
  This task does both assemble and check
• clean
  This task cleans the output of the project.

The new anchor tasks are necessary in order to be able to run regular checks without needing a connected device. Note that build does not depend on deviceCheck, or connectedCheck.

An Android project has at least two outputs: a debug APK and a release APK. Each of these has its own anchor task to facilitate building them separately:

• assemble
• assembleDebug
• assembleRelease

They both depend on other tasks that execute the multiple steps needed to build an APK. The assemble task depends on both, so calling it will build both APKs.

Tip: Gradle support camel case shortcuts for task names on the command line. For instance:

as long as no other task matches ‘aR’

The check anchor tasks have their own dependencies:

• check
• lint
• connectedCheck
• connectedAndroidTest
• deviceCheck
• This depends on tasks created when other plugins implement test extension points.

Finally, the plugin creates tasks for installing and uninstalling all build types (debug, release, test), as long as they can be installed (which requires signing), e.g.

• installDebug
• installRelease
• uninstallAll
• uninstallDebug
• uninstallRelease
• uninstallDebugAndroidTest

The Android plugin provides a broad DSL to customize most things directly from the build system.

Manifest entries

Through the DSL it is possible to configure the most important manifest entries, like these:

• minSdkVersion
• targetSdkVersion
• versionCode
• versionName
• applicationId (the effective packageName — see ApplicationId versus PackageName for more information)
• testApplicationId (used by the test APK)
• testInstrumentationRunner

Example:

android {
    compileSdkVersion 23
    buildToolsVersion "23.0.1"

    defaultConfig {
        versionCode 12
        versionName "2.0"
        minSdkVersion 16
        targetSdkVersion 23
    }
}

The power of putting these manifest properties in the build file is that the values can be chosen dynamically. For instance, one could be reading the version name from a file or using other custom logic:

def computeVersionName() {
    ...
}

android {
    compileSdkVersion 23
    buildToolsVersion "23.0.1"

    defaultConfig {
        versionCode 12
        versionName computeVersionName()
        minSdkVersion 16
        targetSdkVersion 23
    }
}

This configuration is done through an object called a BuildType. By default, 2 instances are created, a debug and a release one. The Android plugin allows customizing those two instances as well as creating other Build Types. This is done with the buildTypes DSL container:

android {
    buildTypes {
        debug {
            applicationIdSuffix ".debug"
        }


        jnidebug {
            initWith(buildTypes.debug)
            applicationIdSuffix ".jnidebug"
            jniDebuggable true
        }
    }
}

Like any other source sets, the location of the build type source set can be relocated:

Additionally, for each Build Type, a new assemble<BuildTypeName> task is created, e.g. assembleDebug. The assembleDebug and assembleRelease tasks have already been mentioned, and this is where they come from. When the debug and release Build Types are pre-created, their tasks are automatically created as well. According to this rule, build.gradle snippet above will also generate an assembleJnidebug task, and assemble would be made to depend on it the same way it depends on the assembleDebug and assembleRelease tasks.

Tip: remember that you can type

gradle aJ to run the assembleJnidebug task.

Possible use case:

• 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).

The code/resources of the BuildType are used in the following way:

• 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.

Signing Configurations

• A keystore
• A keystore password
• A key alias name
• A key password
• The store type

The location, as well as the key name, both passwords and store type form together a Signing Configuration. By default, there is a debug configuration that is setup to use a debug keystore, with a known password and a default key with a known password.
The debug keystore is located in $HOME/.android/debug.keystore, and is created if not present. The debug Build Type is set to use this debug SigningConfig automatically.

It is possible to create other configurations or customize the default built-in one. This is done through the signingConfigs DSL container:

android {
    signingConfigs {
        debug {
            storeFile file("debug.keystore")
        }

        myConfig {
            storeFile file("other.keystore")
            storePassword "android"
            keyAlias "androiddebugkey"
            keyPassword "android"
        }
    }

    buildTypes {
        foo {
            signingConfig signingConfigs.myConfig
        }
    }
}

The above snippet changes the location of the debug keystore to be at the root of the project. This automatically impacts any Build Types that are set to using it, in this case the debug Build Type. It also creates a new Signing Config and a new Build Type that uses the new configuration.

Note: Only debug keystores located in the default location will be automatically created. Changing the location of the debug keystore will not create it on-demand. Creating a SigningConfig with a different name that uses the default debug keystore location will create it automatically. In other words, it’s tied to the location of the keystore, not the name of the configuration.

Note: Location of keystores are usually relative to the root of the project, but could be absolute paths, thought it is not recommended (except for the debug one since it is automatically created).

Gradle projects can have dependencies on other components. These components can be external binary packages, or other Gradle projects.

Dependencies on binary packages

Local packages

To configure a dependency on an external library jar, you need to add a dependency on the compile configuration. The snippet below adds a dependency on all jars inside the libs directory.

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
}

android {
    ...
}

Note: the dependencies DSL element is part of the standard Gradle API and does not belong inside the android element.

The compile configuration is used to compile the main application. Everything in it is added to the compilation classpath and also packaged in the final APK. There are other possible configurations to add dependencies to:

• compile: main application
• androidTestCompile: test application
• debugCompile: debug Build Type
• releaseCompile: release Build Type.

Because it’s not possible to build an APK that does not have an associated Build Type, the APK is always configured with two (or more) configurations: compile and <buildtype>Compile. Creating a new Build Type automatically creates a new configuration based on its name. This can be useful if the debug version needs to use a custom library (to report crashes for instance), while the release doesn’t, or if they rely on different versions of the same library (see Gradle documentation on details of how version conflicts are handled).

Remote artifacts

repositories {
     jcenter()
}

dependencies {
    compile 'com.google.guava:guava:18.0'
}

android {
    ...
}

Note: jcenter() is a shortcut to specifying the URL of the repository. Gradle supports both remote and local repositories.
Note: Gradle will follow all dependencies transitively. This means that if a dependency has dependencies of its own, those are pulled in as well.

For more information about setting up dependencies, read the Gradle user guide here, and DSL documentation here.

Multi project setup

Each projects will have its own build.gradle declaring how it gets built. Additionally, there will be a file called settings.gradle at the root declaring the projects. This gives the following structure:

The content of settings.gradle is very simple. It defines which folder is actually a Gradle project:

The :app project is likely to depend on the libraries, and this is done by declaring the following dependencies:

More general information about multi-project setup here.

Library projects

buildscript {
    repositories {
        jcenter()
    }

    dependencies {
        classpath 'com.android.tools.build:gradle:1.3.1'
    }
}

apply plugin: 'com.android.library'

android {
    compileSdkVersion 23
    buildToolsVersion «23.0.1»
}

This creates a library project that uses API 23 to compile. SourceSets, build types and dependencies are handled the same as they are in an application project and can be customized the same way.

Differences between a Project and a Library Project

Referencing a library is done the same way any other project is referenced:

Note: if you have more than one library, then the order will be important. This is similar to the old build system where the order of the dependencies in the project.properties file was important.

Library Publication

android {
    defaultPublishConfig "flavor1Debug"
}

It is also possible to publish all variants of a library. We are planning to allow this while using a normal project-to-project dependency (like shown above), but this is not possible right now due to limitations in Gradle (we are working toward fixing those as well).

android {
    publishNonDefault true
}

dependencies {
    flavor1Compile project(path: ':lib1', configuration: 'flavor1Release')
    flavor2Compile project(path: ':lib1', configuration: 'flavor2Release')
}

Important: Note that the published configuration is a full variant, including the build type, and needs to be referenced as such. 

There are a few values that can be configured for the test app, in order to configure the <instrumentation> node (see the DSL reference for details)

• testApplicationId
• testInstrumentationRunner

• testHandleProfiling

• testFunctionalTest

As seen previously, those are configured in the defaultConfig object:

The value of the targetPackage attribute of the instrumentation node in the test application manifest is automatically filled with the package name of the tested app, even if it is customized through the defaultConfig and/or the Build Type objects. This is one of the reason this part of the manifest is generated automatically.

Additionally, the androidTest source set can be configured to have its own dependencies. By default, the application and its own dependencies are added to the test app classpath, but this can be extended with the snippet below:

The test app is built by the assembleAndroidTest task. It is not a dependency of the main assemble task, and is instead called automatically when the tests are set to run.

Currently only one Build Type is tested. By default it is the debug Build Type, but this can be reconfigured with:

• Ensure the app and the test app are built (depending on assembleDebug and assembleDebugAndroidTest).
• Install both apps.
• Run the tests.
• Uninstall both apps.

If more than one device is connected, all tests are run in parallel on all connected devices. If one of the test fails, on any device, the build will fail.

The value of android.testOptions.resultsDir is evaluated with Project.file(String)

In a multi project setup with application(s) and library(ies) projects, when running all tests at the same time, it might be useful to generate a single reports for all tests.

To do this, a different plugin is available in the same artifact. It can be applied with:

buildscript {
    repositories {
        jcenter()
    }

    dependencies {
        classpath 'com.android.tools.build:gradle:0.5.6'
    }
}

apply plugin: 'android-reporting'

This should be applied to the root project, ie in build.gradle next to settings.gradle

Then from the root folder, the following command line will run all the tests and aggregate the reports:

Note: the —continue option ensure that all tests, from all sub-projects will be run even if one of them fails. Without it the first failing test will interrupt the run and not all projects may have their tests run.

Lint support

One goal of the new build system is to enable creating different versions of the same application.

There are two main use cases:

1. Different versions of the same application
   For instance, a free/demo version vs the “pro” paid application.
2. Same application packaged differently for multi-apk in Google Play Store.
   See http://developer.android.com/google/play/publishing/multiple-apks.html for more information.
3. A combination of 1. and 2. 

The goal was to be able to generate these different APKs from the same project, as opposed to using a single Library Projects and 2+ Application Projects.

Product flavors

A product flavor defines a customized version of the application build by the project. A single project can have different flavors which change the generated application.

This new concept is designed to help when the differences are very minimum. If the answer to “Is this the same application?” is yes, then this is probably the way to go over Library Projects.

Product flavors are declared using a productFlavors DSL container:

android {
    ....

    productFlavors {
        flavor1 {
            ...
        }

        flavor2 {
            ...
        }
    }
}

Note: The name of the flavors cannot collide with existing Build Type names, or with the androidTest and test source sets.

Build Type + Product Flavor = Build Variant

As we have seen before, each Build Type generates a new APK. Product Flavors do the same: the output of the project becomes all possible combinations of Build Types and, if applicable, Product Flavors. Each (Build Type, Product Flavor) combination is called a Build Variant. For instance, with the default debug and release Build Types, the above example generates four Build Variants:

• Flavor1 — debug
• Flavor1 — release
• Flavor2 — debug
• Flavor2 — release

Projects with no flavors still have Build Variants, but the single default flavor/config is used, nameless, making the list of variants similar to the list of Build Types.

Product Flavor Configuration

Each flavors is configured with a closure:

android {
    ...

    defaultConfig {
        minSdkVersion 8
        versionCode 10
    }

    productFlavors {
        flavor1 {
            applicationId "com.example.flavor1"
            versionCode 20
         }

         flavor2 {
             applicationId "com.example.flavor2"
             minSdkVersion 14
         }
    }
}

Note that the android.productFlavors.* objects are of type ProductFlavor which is the same type as the android.defaultConfig object. This means they share the same properties.

defaultConfig provides the base configuration for all flavors and each flavor can override any value. In the example above, the configurations end up being:

• flavor1
• applicationId: com.example.flavor1
• minSdkVersion: 8
• versionCode: 20
• flavor2
• applicationId: com.example.flavor2
• minSdkVersion: 14
• versionCode: 10

Usually, the Build Type configuration is an overlay over the other configuration. For instance, the Build Type‘s applicationIdSuffix is appended to the Product Flavor‘s applicationId. There are cases where a setting is settable on both the Build Type and the Product Flavor. In this case, it’s is on a case by case basis. For instance, signingConfig is one of these properties. This enables either having all release packages share the same SigningConfig, by setting android.buildTypes.release.signingConfig, or have each release package use their own SigningConfig by setting each android.productFlavors.*.signingConfig objects separately.

Sourcesets and Dependencies

Similar to Build Types, Product Flavors also contribute code and resources through their own sourceSets. The above example creates four sourceSets:

• android.sourceSets.flavor1
  Location src/flavor1/
• android.sourceSets.flavor2
  Location src/flavor2/
• android.sourceSets.androidTestFlavor1
  Location src/androidTestFlavor1/
• android.sourceSets.androidTestFlavor2
  Location src/androidTestFlavor2/

Those sourceSets are used to build the APK, alongside android.sourceSets.main and the Build Type sourceSet. The following rules are used when dealing with all the sourcesets used to build a single APK:

• All source code (src/*/java) are used together as multiple folders generating a single output.
• Manifests are all merged together into a single manifest. This allows Product Flavors to have different components and/or permissions, similarly to Build Types.
• All resources (Android res and assets) are used using overlay priority where the Build Type overrides the Product Flavor, which overrides the main sourceSet.
• Each Build Variant generates its own R class (or other generated source code) from the resources. Nothing is shared between variants.

• android.sourceSets.flavor1Debug
  Location src/flavor1Debug/
• android.sourceSets.flavor1Release
  Location src/flavor1Release/
• android.sourceSets.flavor2Debug
  Location src/flavor2Debug/
• android.sourceSets.flavor2Release
  Location src/flavor2Release/

These have higher priority than the build type sourcesets, and allow customization at the variant level.

Building and Tasks

We previously saw that each Build Type creates its own assemble<name> task, but that Build Variants are a combination of Build Type and Product Flavor.

When Product Flavors are used, more assemble-type tasks are created. These are:

1. assemble<Variant Name>
2. assemble<Build Type Name>
3. assemble<Product Flavor Name>

#1 allows directly building a single variant. For instance assembleFlavor1Debug.

#2 allows building all APKs for a given Build Type. For instance assembleDebug will build both

Flavor1Debug and Flavor2Debug variants.

#3 allows building all APKs for a given flavor. For instance assembleFlavor1 will build both

Flavor1Debug and Flavor1Release variants.

The task assemble will build all possible variants.

In some case, one may want to create several versions of the same apps based on more than one criteria.
For instance, multi-apk support in Google Play supports 4 different filters. Creating different APKs split on each filter requires being able to use more than one dimension of Product Flavors.

Consider the example of a game that has a demo and a paid version and wants to use the ABI filter in the multi-apk support. With 3 ABIs and two versions of the application, 6 APKs needs to be generated (not counting the variants introduced by the different Build Types).
However, the code of the paid version is the same for all three ABIs, so creating simply 6 flavors is not the way to go.
Instead, there are two dimensions of flavors, and variants should automatically build all possible combinations.

This feature is implemented using Flavor Dimensions. Flavors are assigned to a specific dimension:

abi > version > defaultConfig

Multi-flavors projects also have additional sourcesets, similar to the variant sourcesets but without the build type:

These allow customization at the flavor-combination level. They have higher priority than the basic flavor sourcesets, but lower priority than the build type sourcesets.

Testing

Testing multi-flavors project is very similar to simpler projects.

The androidTest sourceset is used for common tests across all flavors, while each flavor can also have its own tests.

As mentioned above, sourceSets to test each flavor are created:

• android.sourceSets.androidTestFlavor1
  Location src/androidTestFlavor1/
• android.sourceSets.androidTestFlavor2
  Location src/androidTestFlavor2/

Similarly, those can have their own dependencies:

Running the tests can be done through the main deviceCheck anchor task, or the main androidTest tasks which acts as an anchor task when flavors are used.

Each flavor has its own task to run tests: androidTest

<VariantName>. For instance:

• androidTestFlavor1Debug
• androidTestFlavor2Debug

Similarly, test APK building tasks and install/uninstall tasks are per variant:

• assembleFlavor1Test
• installFlavor1Debug
• installFlavor1Test
• uninstallFlavor1Debug
• …

Finally the HTML report generation supports aggregation by flavor.
The location of the test results and reports is as follows, first for the per flavor version, and then for the aggregated one:

• build/androidTest-results/flavors/<FlavorName>
• build/androidTest-results/all/
• build/reports/androidTests/flavors<FlavorName>
• build/reports/androidTests/all/

Customizing either path, will only change the root folder and still create sub folders per-flavor and aggregated results/reports.

private void javaCode() {
    if (BuildConfig.FLAVOR.equals("paidapp")) {
        doIt();
    else {
        showOnlyInPaidAppDialog();
    }
}

• boolean DEBUG – if the build is debuggable.
• int VERSION_CODE
• String VERSION_NAME
• String APPLICATION_ID
• String BUILD_TYPE – name of the build type, e.g. «release»
• String FLAVOR – name of the flavor, e.g. «paidapp»

If the project uses flavor dimensions, additional values are generated. Using the example above, here’s an example BuildConfig:

Filtering Variants

When you add dimensions and flavors, you can end up with variants that don’t make sense. For example you may define a flavor that uses your Web API and a flavor that uses hard-coded fake data, for faster testing. The second flavor is only useful for development, but not in release builds. You can remove this variant using the variantFilter closure, like this:

With the configuration above, your project will have only three variants:

android.applicationVariants.all { variant ->
   ....
}

First, Gradle is meant to have the tasks be only configured for input/output location and possible optional flags. So here, the tasks only define (some of) the inputs/outputs.

Second, the input for most of those tasks is non-trivial, often coming from mixing values from the sourceSets, the Build Types, and the Product Flavors. To keep build files simple to read and understand, the goal is to let developers modify the build by tweak these objects through the DSL, rather than diving deep in the inputs and options of the tasks and changing them.

Setting language level

You can use the compileOptions block to choose the language level used by the compiler. The default is chosen based on the compileSdkVersion value.