As you know, one of usage of file certificate is used to access HTTPS from HTTP. If your current host is HTTPS but you still access using HTTP , so by using file certificate it will be redirecting to HTTPS automatically.
Before you adding file certificate to Retrofit 2.0 make you using OKHTTP 3 for your client. So here is the method that you can use for adding file certificate to Retrofit 2.0 :
First import the following package :
Here the method that i use in my project, write the following method (you can modify the method as you wish) :
That's all, hope it helps and works. Thank you.