Khaista Pashto Dari Keyboard is a great keyboard application by The Sher Labs. It helps you change between Dari, Pashto and English with just a swipe on the spacebar.
* Choose between different themes
* Switch between Dari, Pashto and English
* Easy Step by Step guide to setup
* and more...
Instructions on how to install it; https://www.youtube.com/watch?v=sr7j-Zu2c8g