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How to run an Expo app on an Android emulator

When developing an Expo app on a PC you need to be able to run the app on an Android emulator as you don’t have any iOS simulators to work with like you do on a Mac. I found the Expo instructions a little lacking in some detail, and as a Windows PC user primarily, I struggled to find all the information I needed in one place, to run my Expo app in an Android Emulator.

I’m presuming at this point that you’ve created an Expo project, and built your Expo app. You’ll need to download Android Studio and install it, and have at least one emulator configured.

So, to run your Expo app in an Android emulator :

  1. Start Expo by typing expo start on the command line.
  2. Open Android Studio.
  3. Open your project in Android Studio.
  4. Open the ‘AVD manager’ from the Android Studio toolbar.
  5. Run an Android emulator.
  6. Click ‘run on Android device/emulator‘ in the Expo client.

From Android Studio here is the open AVD Manager button:

To run an Android Emulator, click the play symbol next to the one you want to use from the AVD Manager window:

There’s a few problems you can find with each step, so here’s a few things to bear in mind if any of the above steps don’t work.

If you see this message:

“Couldn’t start project on Android: No Android connected device found, and no emulators could be started automatically. Please connect a device or create an emulator (https://docs.expo.io/workflow/android-studio-emulator). Then follow the instructions here to enable USB debugging: https://developer.android.com/studio/run/device.html#developer-device-options. If you are using Genymotion go to Settings -> ADB, select “Use custom Android SDK tools”, and point it at your Android SDK directory.”

…it means that steps 2 and 3 probably haven’t been done. It’s not a particularly obvious message and you’d be surprised ho easy it is to forget both steps.

If you see a message saying:

Couldn’t adb reverse: device ‘adb’ not found

… most of the time if I ignore this and click ‘Run in Android Emulator’ again after a few seconds it runs just fine.

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