how to return data from cupertino picker to bottomsheet?

[Error Place]

hey guys. 

i have a button inside the showmodelbottomsheet that returns a cupertino picket. 

higher up i have a textwidget that should return the value selected from the picker. but it only refresh the value when i close the bottomsheet . how can i make the text widget to get the new value everytime the cupertino closes instead?

best regards all

this is the code. 

 OutlineButton(
  child: Text(
      citys[selectedcity]),
  onPressed: () =>
      showModalBottomSheet(
          context:
              context,
          builder: (BuildContext
                  context) =>
              Container(
                color: Colors.white,
                height: 200,
                width: MediaQuery.of(context).size.width,
                child: CupertinoPicker(
                  onSelectedItemChanged: (int index) {
                    setState(() {
                      selectedcity = index;
                      print(citys[selectedcity]);
                    });
                  },
                  itemExtent: 30,

                  children: List<Widget>.generate(citys.length, (index) {
                    return Center(
                      child: Text(citys[index]),
                    );
                  }),
                ),
              )),
),