How can I change DropdownButton values from another widget in Flutter? - flutter

Question

I am using that DropdownButton inside of the Stateless wigdet but I want to change that DropdownButton values from another Stateful widget. Likewise with using DropdownButton value, I want to change another stateless widget's container color.
Here is my First Stateless widget
List<String> dropdownValues = ['red', 'green', 'blue'];
#override
Widget build(BuildContext context) {
return Container(
child: DropdownButton(
items: dropdownValues
.map((value) => DropdownMenuItem(
child: Text(value),
value: value,
))
.toList(),
onChanged: (String newValue) {},
isExpanded: false,
hint: Text('Chose Color'),
selectedItemBuilder: ,
),
);
}
}
This is my Stateful widget
bool isLightOn = false;
#override
Widget build(BuildContext context) {
return Container(
color: Colors.blue,
padding: new EdgeInsets.all(5.0),
child: Column(
children: <Widget>[
LightBulb(
isLightOn: isLightOn,
),
LightButton(
isLightOn: isLightOn,
onButtonPress: onButtonPress,
),
LightColorSelector(),
],
),
);
}
void onButtonPress() {
if (isLightOn == false) {
setState(() {
isLightOn = true;
});
} else {
setState(() {
isLightOn = false;
});
}
}
}
How can I handle these problems and how can I manipulate DropdownButton values?
Likewise, I want to reflect that DropdownButton value with changing LightBulb's container color.
Here is LightBulb class
final bool isLightOn;
LightBulb({this.isLightOn});
#override
Widget build(BuildContext context) {
return Container(
color: isLightOn == false ? Colors.red : Colors.green,
padding: EdgeInsets.all(5.0),
child: isLightOn == false ? Text("OFF") : Text("ON"),
);
}
}

Answer 1

Here is a full working example:
import 'package:flutter/material.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return MaterialApp(
home: MyHomePage(),
);
}
}
class MyHomePage extends StatefulWidget {
#override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
List<String> dropdownValues = ['red', 'green', 'blue'];
String selected;
Color color;
#override
Widget build(BuildContext context) {
return Material(
child: Column(children: <Widget>[
DropdownButton<String>(
items: dropdownValues
.map((value) => DropdownMenuItem(
child: Text(value),
value: value,
))
.toList(),
onChanged: (String newValue) {
setState(() {
selected = newValue;
if (newValue == "red") color = Colors.red;
if (newValue == "green") color = Colors.green;
if (newValue == "blue") color = Colors.blue;
});
},
//isExpanded: false,
hint: Text('Chose Color'),
//selectedItemBuilder: ,
),
Container(
color: color != null ? color : Colors.black,
padding: EdgeInsets.all(5.0),
child: selected != null ? Text(selected) : Text("OFF", style: TextStyle(color: Colors.white)),
)
]),
);
}
}