I had facing this issue alot of times. I was playing a realm a month ago and everything is fine. I wanted to play today and everytime I enter, controls, mobs, players and their g amertags, foodbar, hotbar, my doll, my inventory, scoreboard, and even the pause and chat button disappear. I tried reinstalling minecraft and restarting my device and nothing happened. However, i can still move and choose things in my hot bar but i don't see them.
Note:minecraft v1.9.0 - Samsung galaxy Tab E