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 already, you can create a blank one to be able to reach the Virtual Device Manager screen.

Refer to:

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

Cloning an Image

Running tests on two emulators is twice as fast as running on one. Rather than use the UI to create additional avds, you can clone an existing one via:

tools/android/emulator/ \
    --source-ini ~/.android/avd/EMULATOR_ID.ini \
    --dest-ini ~/.android/avd/EMULATOR_ID_CLONED.ini \
    --display-name "Cloned Emulator"

Starting an Emulator from the Command Line

Refer to:

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.