To know currency faster than anybody you can open ADC - Currency Rate. ADC - Currency Rate will give you realtime currency rate. Currency data is taken from fixer.io. ADC - Currency Rate is developed for education purpose. ADC - Currency Rate use some android framework :
1. Retrofit
2. Gson
Feel free to use it and learn about this. Source code link https://github.com/adikwidiasmono/ADC-CurrencyRate . For detail please contact me at adik.widiasmono@gmail.com