How to fix Expected Android API level 21+ but was 19 in Android

Question

In my application i want get data from server, for get connect to server i used Retrofit, OkHttp.
But when running application, show me

Answer 1

Use version 3.11.0 for api level below 21

 implementation 'com.squareup.okhttp3:okhttp:3.11.0'
 implementation 'com.squareup.okhttp3:logging-interceptor:3.11.0'