What knowledge is needed to write such an application (see picture)?

Question

Java

Hello!
Interested in mobile development. As the first application, I want to write a similarity of the famous game 4 pictures 1 word, which would then be put on Google Play.
My question is the following: what knowledge is needed to write such an application? What to study first? What to focus more on? (android api or java graphical libraries)
There is experience in creating programs with a graphical interface, only in C ++ and using SDL2

Answer 1

Well if you want

upload to Google Play

,
it would be logical to use the Android SDK.
In this case, graphics
engines such as LibGDX will be redundant. Standard
android ui elements will suffice.
But, if you want to make a cross-platform game with a good design
and interface, then take a look at LibGDX.
Links to standard courses (free, blue button):
Android by Google
LibGDX and 2d Platformer