com.android.builder.testing.api.DeviceException: No connected devices

Question

Scanning folders for symlinks in /home/sino/Desktop/we-clone/node_modules (4ms)
Starting JS server...
Building and installing the app on the device (cd android &         


        

Answer 1

If you have android studio installed(if not install it) launch android studio with a dummy project, go to Tools -> AVD Manager. Make sure that you create a virtual device and start it.

Note: To create this virtual device you will need to download and install a compatible OS (compatible with your project's Android SDK version - SDK version can be found inside build.gradle file) on it before launching. AVD Manager will guide you with the process.

Another thing, you may be using a real Android device not an emulator and still get this message. If your device is connected through USB to your laptop you need to first enable the developer options:

If using stock Android, go to Settings > About phone > Build number. On a Samsung Galaxy device, go to Settings > About device > Build number. On an HTC device, go to Settings > About > Software information > More > Build number. On an LG device, go to Settings > About phone > Software info > Build number. Tap Build number seven times. After the first few taps, you should see the steps counting down until you unlock the developer options. Once activated, you will see a message that reads, “You are now a developer!” Go back to Settings, where you’ll find a Developer options entry in the menu. (https://www.digitaltrends.com/mobile/how-to-get-developer-options-on-android/)

Then inside developer options, you should enable USB debugging.

Answer 2

You'll need to have an Android Emulator running or a physical device connected and in usb debugging mode.

See https://facebook.github.io/react-native/docs/getting-started.html#preparing-the-android-device for more information.