exampleofstatefulwidget.dart

class SelectColor extends StatefulWidget {
 @override
 _SelectColorState createState() => _SelectColorState();
}

class _SelectColorState extends State<SelectColor> {
 final List<String> _colors = ['Red', 'Green', 'Blue'];
 String _selectedColor;
  
 @override
 Widget build(BuildContext context) {
 return Column(
 children: <Widget>[
 DropdownButton(
 value: _selectedColor,
 items: _colors.map((String color) {
 return DropdownMenuItem(
 value: color,
 child: Text(color),
 );
 }).toList(),
 onChanged: (value) {
 setState(() {
 _selectedColor = value;
 });
 },
 ),
 Text('Selected: ${_selectedColor ?? "}'),
 ],
 );
 }
}