# create assets folder in the current project
$ mkdir android/app/src/main/assets

# create bundle script
$ react-native bundle --platform android --dev false --entry-file index.js --bundle-output android/app/src/main/assets/index.android.bundle --assets-dest android/app/src/main/res/

# execute command to run android to create debug apk
$ react-native run-android

# Or change to android folder
$ cd android

# build debug apk
$ ./gradlew assembleDebug

# build release/unsigned apk
$ ./gradlew assembleRelease