I have a mobile web page of the following format:
header - logo etc - absolute positioned
content - scrollable, absolute positioned
footer, 40px abs
I found a CSS solution that works very well.
You can do a css query for a window screen of 300px height o less, that is the mostly screen height of phones with the software keyboard displayed. It works very fast and very well. For example
@media screen and (max-height: 300px) {
#myinputtext{
position: absolute;
top: 50px;
}
}