depot/third_party/nixpkgs/doc/languages-frameworks/android.section.md

Android

The Android build environment provides three major features and a number of supporting features.

Deploying an Android SDK installation with plugins

The first use case is deploying the SDK with a desired set of plugins or subsets of an SDK.

with import <nixpkgs> {};

let
  androidComposition = androidenv.composeAndroidPackages {
    toolsVersion = "26.1.1";
    platformToolsVersion = "30.0.5";
    buildToolsVersions = [ "30.0.3" ];
    includeEmulator = false;
    emulatorVersion = "30.3.4";
    platformVersions = [ "28" "29" "30" ];
    includeSources = false;
    includeSystemImages = false;
    systemImageTypes = [ "google_apis_playstore" ];
    abiVersions = [ "armeabi-v7a" "arm64-v8a" ];
    cmakeVersions = [ "3.10.2" ];
    includeNDK = true;
    ndkVersions = ["22.0.7026061"];
    useGoogleAPIs = false;
    useGoogleTVAddOns = false;
    includeExtras = [
      "extras;google;gcm"
    ];
  };
in
androidComposition.androidsdk

The above function invocation states that we want an Android SDK with the above specified plugin versions. By default, most plugins are disabled. Notable exceptions are the tools, platform-tools and build-tools sub packages.

The following parameters are supported:

• toolsVersion, specifies the version of the tools package to use
• platformsToolsVersion specifies the version of the platform-tools plugin
• buildToolsVersions specifies the versions of the build-tools plugins to use.
• includeEmulator specifies whether to deploy the emulator package (false by default). When enabled, the version of the emulator to deploy can be specified by setting the emulatorVersion parameter.
• cmakeVersions specifies which CMake versions should be deployed.
• includeNDK specifies that the Android NDK bundle should be included. Defaults to: false.
• ndkVersions specifies the NDK versions that we want to use. These are linked under the ndk directory of the SDK root, and the first is linked under the ndk-bundle directory.
• ndkVersion is equivalent to specifying one entry in ndkVersions, and ndkVersions overrides this parameter if provided.
• includeExtras is an array of identifier strings referring to arbitrary add-on packages that should be installed.
• platformVersions specifies which platform SDK versions should be included.

For each platform version that has been specified, we can apply the following options:

• includeSystemImages specifies whether a system image for each platform SDK should be included.
• includeSources specifies whether the sources for each SDK version should be included.
• useGoogleAPIs specifies that for each selected platform version the Google API should be included.
• useGoogleTVAddOns specifies that for each selected platform version the Google TV add-on should be included.

For each requested system image we can specify the following options:

• systemImageTypes specifies what kind of system images should be included. Defaults to: default.
• abiVersions specifies what kind of ABI version of each system image should be included. Defaults to: armeabi-v7a.

Most of the function arguments have reasonable default settings.

You can specify license names:

• extraLicenses is a list of license names. You can get these names from repo.json or querypackages.sh licenses. The SDK license (android-sdk-license) is accepted for you if you set accept_license to true. If you are doing something like working with preview SDKs, you will want to add android-sdk-preview-license or whichever license applies here.

Additionally, you can override the repositories that composeAndroidPackages will pull from:

• repoJson specifies a path to a generated repo.json file. You can generate this by running generate.sh, which in turn will call into mkrepo.rb.
• repoXmls is an attribute set containing paths to repo XML files. If specified, it takes priority over repoJson, and will trigger a local build writing out a repo.json to the Nix store based on the given repository XMLs.

repoXmls = {
  packages = [ ./xml/repository2-1.xml ];
  images = [
    ./xml/android-sys-img2-1.xml
    ./xml/android-tv-sys-img2-1.xml
    ./xml/android-wear-sys-img2-1.xml
    ./xml/android-wear-cn-sys-img2-1.xml
    ./xml/google_apis-sys-img2-1.xml
    ./xml/google_apis_playstore-sys-img2-1.xml
  ];
  addons = [ ./xml/addon2-1.xml ];
};

When building the above expression with:

$ nix-build

The Android SDK gets deployed with all desired plugin versions.

We can also deploy subsets of the Android SDK. For example, to only the platform-tools package, you can evaluate the following expression:

with import <nixpkgs> {};

let
  androidComposition = androidenv.composeAndroidPackages {
    # ...
  };
in
androidComposition.platform-tools

Using predefined Android package compositions

In addition to composing an Android package set manually, it is also possible to use a predefined composition that contains all basic packages for a specific Android version, such as version 9.0 (API-level 28).

The following Nix expression can be used to deploy the entire SDK with all basic plugins:

with import <nixpkgs> {};

androidenv.androidPkgs_9_0.androidsdk

It is also possible to use one plugin only:

with import <nixpkgs> {};

androidenv.androidPkgs_9_0.platform-tools

Building an Android application

In addition to the SDK, it is also possible to build an Ant-based Android project and automatically deploy all the Android plugins that a project requires.

with import <nixpkgs> {};

androidenv.buildApp {
  name = "MyAndroidApp";
  src = ./myappsources;
  release = true;

  # If release is set to true, you need to specify the following parameters
  keyStore = ./keystore;
  keyAlias = "myfirstapp";
  keyStorePassword = "mykeystore";
  keyAliasPassword = "myfirstapp";

  # Any Android SDK parameters that install all the relevant plugins that a
  # build requires
  platformVersions = [ "24" ];

  # When we include the NDK, then ndk-build is invoked before Ant gets invoked
  includeNDK = true;
}

Aside from the app-specific build parameters (name, src, release and keystore parameters), the buildApp {} function supports all the function parameters that the SDK composition function (the function shown in the previous section) supports.

This build function is particularly useful when it is desired to use Hydra: the Nix-based continuous integration solution to build Android apps. An Android APK gets exposed as a build product and can be installed on any Android device with a web browser by navigating to the build result page.

Spawning emulator instances

For testing purposes, it can also be quite convenient to automatically generate scripts that spawn emulator instances with all desired configuration settings.

An emulator spawn script can be configured by invoking the emulateApp {} function:

with import <nixpkgs> {};

androidenv.emulateApp {
  name = "emulate-MyAndroidApp";
  platformVersion = "28";
  abiVersion = "x86"; # armeabi-v7a, mips, x86_64
  systemImageType = "google_apis_playstore";
}

Additional flags may be applied to the Android SDK's emulator through the runtime environment variable $NIX_ANDROID_EMULATOR_FLAGS.

It is also possible to specify an APK to deploy inside the emulator and the package and activity names to launch it:

with import <nixpkgs> {};

androidenv.emulateApp {
  name = "emulate-MyAndroidApp";
  platformVersion = "24";
  abiVersion = "armeabi-v7a"; # mips, x86, x86_64
  systemImageType = "default";
  useGoogleAPIs = false;
  app = ./MyApp.apk;
  package = "MyApp";
  activity = "MainActivity";
}

In addition to prebuilt APKs, you can also bind the APK parameter to a buildApp {} function invocation shown in the previous example.

Notes on environment variables in Android projects

• ANDROID_SDK_ROOT should point to the Android SDK. In your Nix expressions, this should be ${androidComposition.androidsdk}/libexec/android-sdk. Note that ANDROID_HOME is deprecated, but if you rely on tools that need it, you can export it too.
• ANDROID_NDK_ROOT should point to the Android NDK, if you're doing NDK development. In your Nix expressions, this should be ${ANDROID_SDK_ROOT}/ndk-bundle.

If you are running the Android Gradle plugin, you need to export GRADLE_OPTS to override aapt2 to point to the aapt2 binary in the Nix store as well, or use a FHS environment so the packaged aapt2 can run. If you don't want to use a FHS environment, something like this should work:

let
  buildToolsVersion = "30.0.3";

  # Use buildToolsVersion when you define androidComposition
  androidComposition = <...>;
in
pkgs.mkShell rec {
  ANDROID_SDK_ROOT = "${androidComposition.androidsdk}/libexec/android-sdk";
  ANDROID_NDK_ROOT = "${ANDROID_SDK_ROOT}/ndk-bundle";

  # Use the same buildToolsVersion here
  GRADLE_OPTS = "-Dorg.gradle.project.android.aapt2FromMavenOverride=${ANDROID_SDK_ROOT}/build-tools/${buildToolsVersion}/aapt2";
}

If you are using cmake, you need to add it to PATH in a shell hook or FHS env profile. The path is suffixed with a build number, but properly prefixed with the version. So, something like this should suffice:

let
  cmakeVersion = "3.10.2";

  # Use cmakeVersion when you define androidComposition
  androidComposition = <...>;
in
pkgs.mkShell rec {
  ANDROID_SDK_ROOT = "${androidComposition.androidsdk}/libexec/android-sdk";
  ANDROID_NDK_ROOT = "${ANDROID_SDK_ROOT}/ndk-bundle";

  # Use the same cmakeVersion here
  shellHook = ''
    export PATH="$(echo "$ANDROID_SDK_ROOT/cmake/${cmakeVersion}".*/bin):$PATH"
  '';
}

Note that running Android Studio with ANDROID_SDK_ROOT set will automatically write a local.properties file with sdk.dir set to $ANDROID_SDK_ROOT if one does not already exist. If you are using the NDK as well, you may have to add ndk.dir to this file.

An example shell.nix that does all this for you is provided in examples/shell.nix. This shell.nix includes a shell hook that overwrites local.properties with the correct sdk.dir and ndk.dir values. This will ensure that the SDK and NDK directories will both be correct when you run Android Studio inside nix-shell.

Notes on improving build.gradle compatibility

Ensure that your buildToolsVersion and ndkVersion match what is declared in androidenv. If you are using cmake, make sure its declared version is correct too.

Otherwise, you may get cryptic errors from aapt2 and the Android Gradle plugin warning that it cannot install the build tools because the SDK directory is not writeable.

android {
    buildToolsVersion "30.0.3"
    ndkVersion = "22.0.7026061"
    externalNativeBuild {
        cmake {
            version "3.10.2"
        }
    }
}

Querying the available versions of each plugin

repo.json provides all the options in one file now.

A shell script in the pkgs/development/mobile/androidenv/ subdirectory can be used to retrieve all possible options:

./querypackages.sh packages

The above command-line instruction queries all package versions in repo.json.

Updating the generated expressions

repo.json is generated from XML files that the Android Studio package manager uses. To update the expressions run the generate.sh script that is stored in the pkgs/development/mobile/androidenv/ subdirectory:

./generate.sh