how to show keyboard on flutter code example

Example: how i can call keboard in flutter

class YourState extends StatelessWidget {  
FocusNode inputNode = FocusNode();
void openKeyboard(){
FocusScope.of(context).requestFocus(inputNode)
}

@override
Widget build(BuildContext context) {
  return Scaffold(
  	body:Column(
    children:[
      TextFormField(
          focusNode: inputNode)
      )
      ...
      FlatButton(
          onpress:openKeyboard
      )
    ])
  )
}