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# Gradle project

Host Platform Support (Platform support)
macOS | Windows | Linux
--- | --- | ---
x86‑64 | arm64 | x86 | x86‑64 | arm64 | x86 | x86‑64 | arm | arm64
● | ○ |  | ● |  | △ | ● | △ | △

When generating an Android project, Briefcase produces a Gradle project.

## Environment

Gradle requires an install of a Java 17 JDK and the Android SDK.

If the methods below fail to find an Android SDK or Java JDK, Briefcase will download and install an isolated copy in its data directory.

### Java JDK

If you have an existing install of a Java 17 JDK, it will be used by Briefcase if the `JAVA_HOME` environment variable is set. On macOS, if `JAVA_HOME` is not set, Briefcase will use the `/usr/libexec/java_home` tool to find an existing JDK install.

### Android SDK

If you have an existing install of the Android SDK, it will be used by Briefcase if the `ANDROID_HOME` environment variable is set. If `ANDROID_HOME` is not present in the environment, Briefcase will honor the deprecated `ANDROID_SDK_ROOT` environment variable. Additionally, an existing SDK install must have version 12.0 of Command-line Tools installed; this version can be installed in the SDK Manager in Android Studio.

## Packaging format

Briefcase supports three packaging formats for an Android app:

1. An AAB bundle (the default output of `briefcase package android`, or by using `briefcase package android -p aab`); or

2. A Release APK (by using `briefcase package android -p apk`); or

3. A Debug APK (by using `briefcase package android -p debug-apk`).

## Icon format

Android projects use `.png` format icons, in round, square and adaptive variants. An application must provide the icons in the following sizes, for 3 variants:

- `round`:

  - 48px (`mdpi`; baseline resolution)

  - 72px (`hdpi`; 1.5x scale)

  - 96px (`xhdpi`; 2x scale)

  - 144px (`xxhdpi`; 3x scale)

  - 192px (`xxxhdpi`; 4x scale)

- `square`:

  - 48px (`mdpi`; baseline resolution)

  - 72px (`hdpi`; 1.5x scale)

  - 96px (`xhdpi`; 2x scale)

  - 144px (`xxhdpi`; 3x scale)

  - 192px (`xxxhdpi`; 4x scale)

  - 320px (`mdpi`; baseline resolution for splash screen)

  - 480px (`hdpi`; 1.5x scale for splash screen)

  - 640px (`xhdpi`; 2x scale for splash screen)

  - 960px (`xxhdpi`; 3x scale for splash screen)

  - 1280px (`xxxhdpi`; 4x scale for splash screen)

- `adaptive`:

  - 108px (`mdpi`; baseline resolution; 66px drawable area)

  - 162px (`hdpi`; 1.5x scale; 99px drawable area)

  - 216px (`xhdpi`; 2x scale; 132px drawable area)

  - 324px (`xxhdpi`; 3x scale; 198px drawable area)

  - 432px (`xxxhdpi`; 4x scale; 264px drawable area)

The `round` and `square` icons should include their background color in the image. The `adaptive` icons should have a transparent background; the icon image should be centered in the overall image, and should not exceed the drawable area. The background color of the adaptive icon will be the value specified with `splash_background_color`.

The icon will also be used to populate the splash screen. You can specify a background color for the splash screen using the `splash_background_color` configuration setting.

Android projects do not support installer images.

## Colors

Android allows for some customization of the colors used by your app:

- `base_theme` is used to set the base Android theme.

- `accent_color` is used as a subtle highlight throughout your app to call attention to key elements. It’s used on things like form labels and inputs.

- `primary_color` is the main branding color of the app and is used to color the app bar in the main window.

- `primary_color_dark` is used alongside the primary color to color the status bar at the top of the screen.

- `splash_background_color` is the color of the splash background that displays while an app is loading.

## Additional options

The following options can be provided at the command line when producing Android projects:

### run

#### `-d <device>` / `--device <device>`

The device or emulator to target. Can be specified as:

- `@` followed by an AVD name (e.g., `@beePhone`); or

- a device ID (a hexadecimal identifier associated with a specific hardware device); or

- a JSON dictionary specifying the properties of a device that will be created. This dictionary must have, at a minimum, an AVD name:

      $ briefcase run -d '{"avd":"new-device"}'

  You may also specify:

  - `device_type` (e.g., `pixel`) - the type of device to emulate

  - `skin` (e.g., `pixel_3a`) - the skin to apply to the emulator

  - `system_image` (e.g., `system-images;android-31;default;arm64-v8a`) - the Android system image to use in the emulator.

  If any of these attributes are not specified, they will fall back to reasonable defaults.

#### `--Xemulator=<value>`

A configuration argument to be passed to the emulator on startup. For example, to start the emulator in “headless” mode (i.e., without a display window), specify `--Xemulator=-no-window`. See the Android documentation for details on the full list of options that can be provided.

You may specify multiple `--Xemulator` arguments; each one specifies a single argument to pass to the emulator, in the order they are specified.

#### `--shutdown-on-exit`

Instruct Briefcase to shut down the emulator when the run finishes. This is especially useful if you are running in headless mode, as the emulator will continue to run in the background, but there will be no visual manifestation that it is running. It may also be useful as a cleanup mechanism when running in a CI configuration.

## Application configuration

The following options can be added to the `tool.briefcase.app.<appname>.android` section of your `pyproject.toml` file.

### `android_manifest_attrs_extra_content`

Additional attributes that will be added verbatim to the `<manifest>` declaration of the `AndroidManifest.xml` of your app.

### `android_manifest_extra_content`

Additional content that will be added verbatim just before the closing `</manifest>` declaration of the `AndroidManifest.xml` of your app.

### `android_manifest_application_attrs_extra_content`

Additional attributes that will be added verbatim to the `<application>` declaration of the `AndroidManifest.xml` of your app.

### `android_manifest_application_extra_content`

Additional content that will be added verbatim just before the closing `</application>` declaration of the `AndroidManifest.xml` of your app.

### `android_manifest_activity_attrs_extra_content`

Additional attributes that will be added verbatim to the `<activity>` declaration of the `AndroidManifest.xml` of your app.

### `android_manifest_activity_extra_content`

Additional content that will be added verbatim just before the closing `</activity>` declaration of the `AndroidManifest.xml` of your app.

### `base_theme`

The base theme for the application. Defaults to `Theme.AppCompat.Light.DarkActionBar`

### `build_gradle_dependencies`

The list of libraries that should be linked into the Android application. Each library should be a versioned Maven package specifier. If unspecified, three libraries will be linked into the app:

- `androidx.appcompat:appcompat:1.0.2`

- `androidx.constraintlayout:constraintlayout:1.1.3`

- `androidx.swiperefreshlayout:swiperefreshlayout:1.1.0`

### `build_gradle_extra_content`

A string providing additional Gradle settings to use when building your app. This will be added verbatim to the end of your `app/build.gradle` file.

### `feature`

A property whose sub-properties define the features that will be marked as required by the final app. Each entry will be converted into a `<uses-feature>` declaration in your app’s `AndroidManifest.xml`, with the feature name matching the name of the sub-attribute.

For example, specifying:

    feature."android.hardware.bluetooth" = true

will result in an `AndroidManifest.xml` declaration of:

    <uses-feature android:name="android.hardware.bluetooth" android:required="true">

The use of some cross-platform permissions will imply the addition of features; see the discussion on Android permissions for more details.

### `permission`

A property whose sub-properties define the platform-specific permissions that will be marked as required by the final app. Each entry will be converted into a `<uses-permission>` declaration in your app’s `AndroidManifest.xml`, with the feature name matching the name of the sub-attribute.

For example, specifying:

    permission."android.permission.HIGH_SAMPLING_RATE_SENSORS" = true

will result in an `AndroidManifest.xml` declaration of:

    <uses-permission android:name="android.permission.HIGH_SAMPLING_RATE_SENSORS">

### `version_code`

In addition to a version number, Android projects require a version “code”. This code is an integer version of your version number that must increase with every new release pushed to the Play Store.

Briefcase will attempt to generate a version code by combining the version number with the build number. It does this by using each part of the main version number (padded to 3 digits if necessary) and the build number as 2 significant digits of the final version code:

> - Version `1.0`, build 1 becomes `1000001` (i.e, `1`, `00`, `00`, `01`)

> - Version `1.2`, build 37 becomes `1020037` (i.e., `1`, `02`, `00`, `37`)

> - Version `1.2.37`, build 42 becomes `1023742` (i.e, `1`, `02`, `37`, `42`)

> - Version `2020.6`, build 4 becomes `2020060004` (i.e., `2020`, `06`, `00`, `04`)

If you want to manually specify a version code by defining `version_code` in your application configuration. If provided, this value will override any auto-generated value.

## Permissions

Briefcase cross platform permissions map to `<uses-permission>` declarations in the app’s `AppManifest.xml`:

- `camera`: `android.permission.CAMERA`

- `microphone`: `android.permission.RECORD_AUDIO`

- `coarse_location`: `android.permission.ACCESS_COARSE_LOCATION`

- `fine_location`: `android.permission.ACCESS_FINE_LOCATION`

- `background_location`: `android.permission.ACCESS_BACKGROUND_LOCATION`

- `photo_library`: `android.permission.READ_MEDIA_VISUAL_USER_SELECTED`

Every application will be automatically granted the `android.permission.INTERNET` and `android.permission.NETWORK_STATE` permissions.

Specifying a `camera` permission will result in the following non-required `feature` definitions being implicitly added to your app:

- `android.hardware.camera`,

- `android.hardware.camera.any`,

- `android.hardware.camera.front`,

- `android.hardware.camera.external` and

- `android.hardware.camera.autofocus`.

Specifying the `coarse_location`, `fine_location` or `background_location` permissions will result in the following non-required `feature` declarations being implicitly added to your app:

- `android.hardware.location.network`

- `android.hardware.location.gps`

This is done to ensure that an app is not prevented from installing if the device doesn’t have the given features. You can make the feature explicitly required by manually defining these feature requirements. For example, to make GPS hardware required, you could add the following to the Android section of your `pyproject.toml`:

    feature."android.hardware.location.gps" = True

## Platform quirks

### Availability of third-party packages

Briefcase is able to use third-party packages in Android apps. As long as the package is available on PyPI, or you can provide a wheel file for the package, it can be added to the `requires` declaration in your `pyproject.toml` file and used by your app at runtime.

If the package is pure Python (i.e., it does not contain a binary library), that’s all you need to do. To check whether a package is pure Python, look at the PyPI downloads page for the project; if the wheels provided are have a `-py3-none-any.whl` suffix, then they are pure Python wheels. If the wheels have version and platform-specific extensions (e.g., `-cp311-cp311-macosx_11_0_universal2.whl`), then the wheel contains a binary component.

If the package contains a binary component, that wheel needs to be compiled for Android. PyPI does not currently support uploading Android-compatible wheels, so you can’t rely on PyPI to provide those wheels. Briefcase uses a secondary repository to provide pre-compiled Android wheels.

This repository is maintained by the BeeWare project, and as a result, it does not have binary wheels for every package that is available on PyPI, or even every version of every package that is on PyPI. If you see any of the following messages when building an app for a mobile platform, then the package (or this version of it) probably isn’t supported yet:

- The error “Chaquopy cannot compile native code”

- A reference to downloading a `.tar.gz` version of the package

- A reference to `Building wheels for collected packages: <package>`

It is usually possible to compile any binary package wheels for Android, depending on the requirements of the package itself. If the package has a dependency on other binary libraries (e.g., something like `libjpeg` that isn’t written in Python), those libraries will need to be compiled for Android as well. However, if the library requires build tools that don’t support Android, such as a compiler that can’t target Android, or a PEP517 build system that doesn’t support cross-compilation, it may not be possible to build an Android wheel.

The Chaquopy repository contains tools to assist with cross-compiling Android binary wheels. This repository contains recipes for building the packages that are stored in the secondary package repository. Contributions of new package recipes are welcome, and can be submitted as pull requests. Or, if you have a particular package that you’d like us to support, please visit the issue tracker and provide details about that package.

While it is possible to use briefcase package android to produce an APK or AAB file for distribution, the file is not usable as-is. It must be signed regardless of whether you’re distributing your app through the Play Store, or via loading the APK directly. For details on how to manually sign your code, see the instructions on signing an Android App Bundle.```