docs/android_emulator.md

# Using an Android Emulator
Always use x86 emulators. Although arm emulators exist, they are so slow that
they are not worth your time. 

## Building for Emulation
You need to target the correct architecture via GN args:
```
target_cpu = "x86"
```

## Creating an Emulator Image
By far the easiest way to set up emulator images is to use Android Studio.
If you don't have an [Android Studio project](android_studio.md) already, you
can create a blank one to be able to reach the Virtual Device Manager screen.

Refer to: https://developer.android.com/studio/run/managing-avds.html

Where files live:
 * System partition images are stored within the sdk directory.
 * Emulator configs and data partition images are stored within
   `~/.android/avd/`.

When creating images:
 * Choose a skin with a small screen for better performance (unless you care
   about testing large screens).
 * Under "Advanced":
   * Set internal storage to 4000MB (component builds are really big).
    * Set SD card to 1000MB (our tests push a lot of files to /sdcard).

Known issues:
 * Our test & installer scripts do not work with pre-MR1 Jelly Bean.
 * Component builds do not work on pre-KitKat (due to the OS having a max
   number of shared libraries).
 * Jelly Bean and KitKat images sometimes forget to mount /sdcard :(.
   * This causes tests to fail.
   * To ensure it's there: `adb -s emulator-5554 shell mount` (look for /sdcard)
   * Can often be fixed by editing `~/.android/avd/YOUR_DEVICE/config.ini`.
     * Look for `hw.sdCard=no` and set it to `yes`

## Starting an Emulator from the Command Line
Refer to: https://developer.android.com/studio/run/emulator-commandline.html.

Note: Ctrl-C will gracefully close an emulator.

If running under remote desktop:
```
sudo apt-get install virtualgl
vglrun ~/Android/Sdk/tools/emulator @EMULATOR_ID
```

## Using an Emulator
 * Emulators show up just like devices via `adb devices`
   * Device serials will look like "emulator-5554", "emulator-5556", etc.