Qt 5 virtual keyboard showfullscreen issue

Hello..
i have downloaded below code and compiled successfully.

https://github.com/KDAB/virtual-keyboard-demo

Then Open terminal and fire below command
export QT_IM_MODULE=vkim

then open any QLineEdit or any input Box related application .
So when you click on input box so Virtual Keyboard popup will aperar.

But if i my application running on showFullscreen so it will not displayed on application...
So any one can help me to fix out this issue?
NOTE: This code will work on QT5

Thanks.
DIpen Patel