Solve the problem that does not support fixed under iOS

Our company has a fixed style at the bottom of the page, and whenever the keyboard pops up, iOS will get out of shape (Android doesn't have the problem, as far as I know).

I did a simple deal with the product's approval prior to this (method 1).

Method One:

Focus when the fixed block position into relative, this is the simplest way to deal with.

Here's my little demo.

<! DOCTYPE html>  
Method Two:
 
Position:absolute the position each time you scroll.
 
Here is my little demo,touch when the hidden processing, input focusout and window resize when the fixed position recalculation.
 
<! DOCTYPE html>  
The above is my processing method, perhaps there are deficiencies, welcome everyone to put forward valuable opinions and exchanges.