Item sprites textures cause a huge lag in mcpe espacially when filling an empty hotbar or opening inventory or showing any block ui for example chest,furnace... In addition to lose more than 40% of the game fps,I tried hiding the hud and it helped a lot but I can't see other indicators lile health and hunger bar if I enabled it,and also when the game shows titles on the screen the same thing happens.
When I was playing the beta versions I saw 60fps on the statistics but when I do fill the hotbar,open the inventory the fps decreases to 30-40 and what makes it annoying that it happens in flat and void world.
So a filled hotbar is a lag source and I can't believe that item sprites textures causes this huge lag

To reproduce this:
1-you need a low or mid range android device and I have a mid range one with 4gb ram and an integrated graphic card that supports opengl 3.3 in addition to octa core cpu and I don't open any apps when playing.

2-open the game and create a new world
3-first you'll see that high framerate but when you do the stuff that I said before you'll face the drop.

The things that I mentioned in this bug report:
1-Putting items in the hotbar
2-Opening the inventory or using functionnal blocks(lag by their ui)
3-Showing a title on the screen using /titlecommand

If you couldn't fix this then add the ability to hide the hotbar from the screen.