In flutter, can you set the appbar backgorund to change base on the value of a dropdown box? - flutter

Question

my drop down box cycles through 5 strings
['blue','red','yellow','orange','grey']
I want my appbar title to be that dropdown box and for the value in the dropdown to determine the appbar color
DropDownWidget ddw = DropDownWidget();
var color = {
"blue": Colors.blue,
"red": Colors.red,
"yellow": Colors.yellow,
"orange": Colors.orange,
"grey": Colors.grey,
};
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
centerTitle: true,
title: ddw,
backgroundColor: color[ddw],
),
}
The dropdown (ddw) shows up as the title, no problem.
I made a dictionary with those strings as the keys and the corresponding color as the value, but I am not able to use the string value of the dropdown to change the background.
Any suggestions?

Answer 1

You can copy paste run full code below
You can call setState in onChanged of DropdownButton
code snippet
appBar: AppBar(
backgroundColor: _appbarColor,
...
DropdownButton<Item>(
hint: Text("Select item"),
value: selectedColor,
onChanged: (Item Value) {
setState(() {
selectedColor = Value;
_appbarColor = selectedColor.color;
});
},
working demo
full code
import 'package:flutter/material.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
// This widget is the root of your application.
#override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: MyHomePage(title: 'Flutter Demo Home Page'),
);
}
}
class Item {
const Item(this.name, this.color);
final String name;
final Color color;
}
class MyHomePage extends StatefulWidget {
MyHomePage({Key key, this.title}) : super(key: key);
final String title;
#override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
int _counter = 0;
Color _appbarColor = Colors.blue;
Item selectedColor;
List<Item> colorList = <Item>[
const Item('blue', Colors.blue),
const Item('red', Colors.red),
const Item('yellow', Colors.yellow),
];
void _incrementCounter() {
setState(() {
_counter++;
});
}
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
backgroundColor: _appbarColor,
title: Text(widget.title),
),
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
DropdownButton<Item>(
hint: Text("Select item"),
value: selectedColor,
onChanged: (Item Value) {
setState(() {
selectedColor = Value;
_appbarColor = selectedColor.color;
});
},
items: colorList.map((Item item) {
return DropdownMenuItem<Item>(
value: item,
child: Row(
children: <Widget>[
Container(
height: 15,
width: 15,
color: item.color,
),
SizedBox(
width: 10,
),
Text(
item.name,
style: TextStyle(color: Colors.black),
),
],
),
);
}).toList()),
Text(
'You have pushed the button this many times:',
),
Text(
'$_counter',
style: Theme.of(context).textTheme.headline4,
),
],
),
),
floatingActionButton: FloatingActionButton(
onPressed: _incrementCounter,
tooltip: 'Increment',
child: Icon(Icons.add),
),
);
}
}