I have been using Android Studio in Spanish, and it bothers me that it highlights as incorrect words which are spelt correctly.
Can I add a Spanish dictionary to Android
In Android Studio (1.2.1.1 - 2.3.3) you can find this here:
File -> Settings -> Editor -> Spelling -> Dictionaries, and click "+" sign next to "Custom Dictionaries Folders" grid.
Important Note: You need to use UTF-8 character coding in your "language.dic" file if you would like to use an exotic language like Hungarian, Spanish, Portuguese, etc.