If you sneak and watch at a Villager there will appear a Button that says "open", if you press it there will.happsn nothing. I think that the developers are working on a trading system and that this button should not be visible for 0.16. Using the Archos cobalt 55 plus, android 5.1)
MCPE-17796
Villager Button
Resolved
Fixed
0
(Unassigned)
50152
Confirmed
Tablet - Android - Archos Platinum
Android 5.1
0.16.0, 0.16.2, 1.0.0.1
1.0.0
Retrieved
It turned out that this non-functioning "Open" button has nothing to do with trading. Any entity with a hidden inventory, i.e. a component "minecraft:inventory" whose "container_type" set to "" (default) has the same problem. While villagers are the only entities currently exist in vanilla with such an inventory, you can easily reproduce it with any other entities by modifying their components with a behavior pack.