After learned java, what is the next step to make android apps?

Answer 1

Building an Android app comes down to two major skills/languages: Java and Android. Java is the language used in Android, but the Android part encompasses learning XML for the design of the app, learning the concepts of Android, and using the concepts programmatically with Java.

Once you learn Java and XML (XML is really easy to get used to, and you should learn the language as you program your app rather than learning it beforehand like you would with Java), you need to learn how to connect these two using Android principles :)
@Sololearn

Answer 2

Programming language:-XML, Java Core
IDE:- Android Studio,Genymotion emulator
Complete above requirements and begin developing...
Best of luck