How to detect size of keyboard on device

I want to place a text field exact above the keyboard for that I need to set it position dynamically. For that I need to know keyboard size. Please help me, few people on forum telling it is not possible.  

Please vote for this feature: http://feedback.coronalabs.com/forums/188732-corona-sdk-feature-requests-feedback/suggestions/4267410-get-keyboard-height

Please vote for this feature: http://feedback.coronalabs.com/forums/188732-corona-sdk-feature-requests-feedback/suggestions/4267410-get-keyboard-height