Minecraft Pocket Edition: How to double things.

First you must get what you want to double and put it in the chest.

Then you must close the chest and open it again to get what you put in before.

Now you must walk away and when you get close to the chest, you leave the Minecraft application and close it.

When you go to the Minecraft world, you will have the things you wanted to double in the inventory and in the chest.