How to hide translator API key in android

If i were you i will rent a server (maybe amazon) and create a database and insert our api key with simple encrypted string (hash etc.).

ID - Name - androidKey - key

1 - GoogleAPI - AJKBSASHUA9 - yourAPIKey
2 - YandexAPI - 5A6S5D6A53C - yourAPIKey
.
.
.

Then you can create a service which is run by your android packageName;

http://example.com/API/getAPIKey/
?packageName="yourPackageName"
&androidKey="AJKBSASHUA9"

And if you use POST method it is safe for you.