Thanks for the recommendation. I will describe a little bit my opinion. There is the necessary minimum for all mobile platforms to write code: specialized text editors, some networking tools, primitive graphical editors.
I like this app too: you can directly create a new Java project edit, and run Java code, you can also develop games with powerful built-in tutorials, very suitable for beginners.
You can also test applications like Osulogin, but I suggest you have a powerful modern smartphone for that.