Is it possible to learn Runtime SDK for Android (ESRI) directly without going for learning Android Studio? I am familiar with the terms of Java and Android Studio but not an expert at Android Studio.
Try the tutorial at https://developers.arcgis.com/android/latest/guide/develop-your-first-map-app.htm. It walks you through all the clicks on Android Studio so you don't have to be an expert to get started. However, it's a good idea to get to know Android Studio if you plan to do modern Android development.