How to use virtualkeyboard in popup

[sonicss]

I made a colordialog popup. I want the user can select the color by RGB or HSV. There are one circle and two slider for HSV. A textfield for RGB. When the textfield get focused, the virtualkeyboard displayed. but the virtualkeybord is Main.qml's child. in this case. the virtualkeyboard is masked(as the pics). How do I use the virtualkeyboard in popup?