bool isChecked = false;
Switch(
            activeColor: Colors.purple,
            activeTrackColor: Colors.purple[100],
            inactiveThumbColor: Colors.grey,
            inactiveTrackColor: Colors.grey[400],
            value: isChecked,
            onChanged: (bool value) { 
              setState(() {
                isChecked = value;
              });
             }, 
            ),