Build

m CustomLocale

Install

New install

adb root && adb remount && adb reboot
adb wait-for-device && adb root && adb remount

APP_PATH="/system/priv-app/CustomLocale/"
adb shell mkdir ${APP_PATH} || true
adb push ${OUT}${APP_PATH} ${APP_PATH}
adb reboot

Reinstall

APP_PATH="/system/priv-app/CustomLocale/"
adb install -r ${OUT}${APP_PATH} ${APP_PATH}

How to use

Just launch the activity, or use following ADB command.

adb shell am broadcast -a com.android.intent.action.SET_LOCALE \
   --es com.android.intent.extra.LOCALE ${TARGET_LOCALE} com.android.customlocale2

${TARGET_LOCALE} can be either 2 chars (e.g. en, iw) or 5 chars (e.g. en_US, iw_IL)