# run-android

## Description

* Runs a MiniApp on an Android emulator or connected device  

## Syntax

`ern run-android`

**Options**

`--baseComposite <compositePath>`

* Git or File System path, to the custom Composite repository (refer to the \[custom Composite] documentation for more information).

`--descriptor, -d`

* complete native application descriptor

`--dev [true|false]`

* Enable or disable React Native dev support

`--extra/-e`

* Optional extra configuration specific to local container and runner
* Override the android build config during local container generation and runner project by passing `androidConfig` attributes
  * **As a json string** &#x20;

    For example `--extra '{"androidConfig": {"androidGradlePlugin": "3.2.1","buildToolsVersion": "28.0.3","compileSdkVersion": "28","gradleDistributionVersion": "4.6","minSdkVersion": "19","sourceCompatibility": "VERSION_1_8","supportLibraryVersion": "28.0.0","targetCompatibility": "VERSION_1_8","targetSdkVersion": "28"}}'`   &#x20;
  * **As a file path** &#x20;

    For example `--extra /Users/username/my-container-config.json` &#x20;

    In that case, the configuration will be read from the file. &#x20;
  * **As a Cauldron file path** &#x20;

    For example `--extra cauldron://config/container/my-container-config.json` &#x20;

    In that case, the configuration will be read from the file stored in Cauldron.  &#x20;

    For this way to work, the file must exist in Cauldron (you can add a file to the cauldron by using the \[ern cauldron add file] command).

`--host`

* Host or ip to launch the local packager on *(default: localhost)*

`--launchFlags <string>`

* Extra options passed to `am start` command when launching the application (correspond to the `Launch Flags` in Run/Debug Configurations of application in Android Studio, as can be seen on screenshot below)
* Make sure to use `=` on the command line to provide this option, and keep the string in quotes. For example `--launchFlags="--es aKey aStringValue --ei anotherKey 1"`

![Android Studio Run Config](https://3933244913-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-LF_waG_U-NeI1vhIUwJ%2F-LqnIijeK72sOcRgCDmf%2F-LqnImInlEjOrl_iLAY9%2Fandroid-studio-run-config.png?generation=1570671374625335\&alt=media)

`--mainMiniAppName`

* Name of the MiniApp to launch when starting the Runner application
* If you are running the command from the `MainApp` directory, only specify name of the `MiniApp` (Not the path).

`--miniapps/m`

* One or more MiniApps to combine in the Runner Container

`--port`

* Port on which the local packager should listen on *(default: 8081)*

`--usePreviousDevice/-u`

* Use the previously selected device to avoid prompt

## JavaScript engine

By default Electrode Native will run the MiniApp with a Container that uses JavaScriptCore engine. If you'd rather like to run the MiniApp with [Hermes](https://hermesengine.dev) engine, you should add the following inside the `ern` object of the MiniApp package.json :

```javascript
 "androidConfig": {
  "jsEngine": "hermes"
}
```

## Remarks

* You can launch the MiniApp located in the current working directory or on a connected Android device or running emulator if available. If a connected Android device is not available, the command prompts you to select an emulator to launch from the list of installed emulator images. &#x20;
* The first time you run this command from within a MiniApp directory, it generates an Android directory containing the Android runner application project. If the Android folder already exists (it is not the first run of the `ern run-android` command for this MiniApp), the existing runner project is used. &#x20;
* After the runner project is generated, you can safely make native code modifications to it, knowing that the next time the `ern run-android` command is issued, the project and your changes will remain. &#x20;
* If you want to regenerate the runner project from scratch, remove the Android directory. &#x20;
* The miniapp can be any Yarn package descriptor, including Git or other file system path schemes. &#x20;
* The `ern run-android` command is the `ern` equivalent of the `react-native run-android` command.
* If you are running the command from the `MainApp` directory, only specify name of the `MiniApp` (Not the path) in the `--mainMiniAppName` option.

\[custom Composite]: ./platform-parts/composite/index.md