Flutter how to store selected values from the DropdownButton?

Question

How could I make the selected item from the dropdownButton to store the current selected min and max value of the json in to minTip and maxTip.

A small sample of my code below:

 String minTip;
 String maxTip;
 String _mySelection;

  List<Map> _myJson = [
    {"id": "1", "name": "Restaurant", "min": "10", "max": "20"},
    {"id": "2", "name": "Delivery", "min": "5", "max": "15"}
  ];

DropdownButton<String>(
                value: _mySelection,
                style: TextStyle(color: Colors.orange),
                onChanged: (String newValue) {
                  setState(() {
                    _mySelection = newValue;
                  });
                },
                items: _myJson.map((Map map) {
                  return DropdownMenuItem<String>(
                    child: new Text(map["name"]),
                    value: map["id"].toString(),
                  );
                }).toList(),
              ),